1

Thesis Paper

Alien Invasive Plant Species in Bangladesh and Their

Impact on Indigenous Plant Biodiversity

A dissertation presented (by Mohammad Redowan) as a requirement for the degree of 1-year professional Master of Science (M.Sc.) degree

in Forestry, Institute of Forestry & Environmental Sciences,

University of Chittagong Chittagong, Bangladesh

Guided By

Dr. Mohammed Kamal Hossain

Associate Professor

Institute of Forestry and

Environmental Sciences

University of Chittagong

Submitted by

Mohammad Redowan

MSc student

Session: 2004-2005

Institute of Forestry and

Environmental Sciences

University of Chittagong

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Chapter 1: Introduction

1.1. Introduction

The word ‘alien’ denotes ‘foreign’ or ‘exotic’ and ‘invasive’ indicates which

violates the rights of others’. So, alien invasive species are those that occur outside their

natural range or have established themselves accidentally or introduced deliberately to any

land and being established there suppressing the native vegetation. An alien species, also

called ‘non-native’, ‘non-indigenous’, or ‘exotic’, is one that is introduced, accidentally or

purposefully, into an ecosystem in which it did not evolve. Alien or exotic species can

come from other continents, other countries and even other parts of the same country

(Winkler and Herding, 2004). Here ‘foreign’ or ‘exotic’ actually is not justified by

political boundary rather natural range of origin of the plants and their movement outside

to that range is the point of concern.

All alien plants may be exotic, but all exotic plants may not be alien. Alien species

do not always become invasive. To conserve native species and ecosystems appropriately,

we must judge which alien species should be given the highest priority as “invasive alien

species” in management programs. Native plant species may occasionally show invasive

behaviour in ecosystems modified by human activities (Brisson, 2003).

Invasive alien species are those that threaten the existence of native plants and

animals or other aspects of biodiversity and occur in all groups of plants and animals

(Gregorio, 2002). The problem of invasive species is increasingly being recognized around

the world. Invasive alien species can cause severe disruption to both natural and managed

ecosystems (Weber, 2003).

Awareness of the impacts of invasive alien species on biodiversity and human

livelihoods has grown greatly. Information on the topic has burgeoned, invasion biology

has become a recognized science and local actions and international agreements against

IAS have increased (Joan, 2003). Invasive alien species (IAS) are considered to be the

second largest threat for biodiversity loss on a worldwide scale as is reflected in recent

international conventions and politics (CBD, 2001).

The issue of alien invasive species and their use or abuse has generated a lot of

controversy all around the world including Bangladesh. Invasion biology has progressed

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substantially in the past decade (Mackinnon, 2002). Invasions are occurring around the

word at an unprecedented rate and scale (Anon, 2003). But the nation’s approach to

invasive species remains in the dark.

From over a long time, many alien species have been introduced in Bangladesh

with the belief that it would increase the total production (Das, 1982). Most of them have

become naturalized and integrated into the local ecosystem and have little adverse impacts

on the ecosystem but many of them have become invasive. They are damaging our

ecosystem, invading agriculture or natural habitat and displacing indigenous species.

Increasing human population and per capita consumption, leading to expansion of global

trade and increases in human mobility have resulted in unprecedented invasion by

nonnative species.

These biological invasions produce severe, often irreversible impacts on

agriculture, recreation, and our natural resources. Invasive species threaten biodiversity,

habitat quality, and ecosystem function (Daehler and Carino, 1999). They are the second

most important threat to native species, behind habitat destruction, contributing to the

decline of endangered and threatened species. Introduced species also present an ever-

increasing threat to food and fiber production (Gregorio, 2002). In Bangladesh, like other

parts of the world, the economic costs of nonnative species invasions is anticipated to

millions of taka each year .If they are given an inch, they will take an acre!

Invasions by both native and exotic species potentially can threaten natural

communities (Stanton et al., 2003). Invasives threaten the productivity of the soils and

waters upon which our economies and we depend. They imperil the native species that

make this country unique. In sum, the devastation done by non-native invasive species is

one of the most serious and least-recognized tragedies of our time (Yan, 2003). Invasive

species can change the ecosystem composition and function; reduce the indigenous

biological diversity that in extreme case may lead to local extinction of species.

Unfortunately a large number of alien species have been introduced in our

ecosystems without proper scientific investigation on possible impacts. Thus, not all, but a

good number of the species so far been introduced in Bangladesh have become invasive.

The incredible variety of species that have the ability not just to travel in ingenious ways,

but also to establish, thrive and dominate in new places. More than 300 exotic species are

supposed to either wildly growing or cultivated as an economic crop in Bangladesh. Of

them the herbaceous and lianas are the dominant exotics followed by trees an shrubs

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(Islam, 1991). Most of the plants have been brought by settlers, invaders, seamen and

traders. The origins of most of the exotics are Africa, Australia and South America. In

Bangladesh there are no detail records of exotic plants except the plants of some common

and few cultivated ones (Das, 1982). Though the undisturbed natural forests are resistant

to such invasion, but the degraded and secondary forest areas and wastelands are

aggressively invaded by the invasive species.

Foresters have consistently introduced exotic trees for plantations. There is often a

short-term advantage in planting a species in the place where its natural pests and diseases

are absent. In some cases such species spread out of control, displacing natural vegetation

and profoundly changing the natural ecology. Exotic species are not automatically “bad”.

Most of our important food crops and domesticated animals are exotic. But, both exotic

and native species become problems when they are invasive (Mackinnon, 2002).

Despite frequent implied association in the literature, invasiveness and exotic

status are not really closely correlated. Most aliens in Bangladesh are not exotic weeds,

whilst some natives are. The term ‘invasive’ should only be applied to alien species, whilst

for native we should use the less pejorative term ‘expanding’, which is more like semantic

politics than an objective assessment. Invasive alien species in this literature would remain

restricted to Invasive Alien Plant Species only.

1.2. Objectives:

1. To identify the possible invasive plant species in Bangladesh;

2. To determine the distribution of invasive plant species in Bangladesh;

3. To determine the effect of invasive trees Acicia auriculiformis, Eucalyptus

camaldulensis and Melaleuca leucadendron on indigenous plants.

4. To study the habitat, vegetative characteristics, growth and biomass of

invasive shrubs Lantana camara, Eupatorium odoratum, Ipomea carnea and

Mikania cordata and their impact on indigenous plant species.

1.3. Rationale of the research

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Biological invasion is a worldwide problem. Bangladesh like many other countries

of the world faces the problem with alien invasive species whether these are plants or

animals. These invasive species are causing huge loss to our ecosystem, which is not yet

quantified, but the damage to our environment and biodiversity is only felt. Many species

of plants has been introduced here in Bangladesh, many of which are blamed rigorously as

the invasive plants, which are aggressively invading the ecosystems. Some species like

Acacia auriculiformis, Melaleuca leucodendron, Imperata cylindrica, Lantana camara,

Mikania coudata, Ipomea carnea, Eupatorium odoratum have notorious past of ecosystem

invasion in different countries of the world. Lantana camara, Eupatorium odoratum,

Mikania cordata, Ipomea carnea etc are self-spreading aggressive weeds in Bangladesh

ecosystem like many other countries. Imperate cylindrica is a notorious weed in 73

countries of the world (Holm et al., 1977). Eucalyptus and Acacia species have already

spreaded to more than 80 countries of the world (Anon, 2003). Melaleuca also constitute

significant health hazard because of flowers and new foliage airborne substance

production that cause severe asthma-like symptom in sensitive people and also displace

native vegetation (Pernas and Francois, 2003).

But Acacia auriculiformis, Eucalyptus camaldulensis, Acacia mangium etc.

constitutes a substantial part of the plantation program of Bangladesh while they are

problem species in many countries. Lantana camara, Eupatorium odoratum, Mikania

cordata, Ipomea carnea etc are common invasive weeds of fallow land, waste land,

roadside, grassland, canal bank and forests in Bangladesh. Lantana camara and

Eupatorium odoratum are listed weed of 100 of the world’s most invasive species (IUCN, 2003).

Within the last two or three years the work on the problems caused by invasive alien

species has intensified (Ema and Alzbeta, 2004). Attempt has been made in this research

work to investigate the phenomena as what impacts do the trees, Acacia auriculiformis,

Eucalyptus camaldulensis and Melaleuca leucodendron impose to indigenous plant

biodiversity. The vegetative characteristics of Lantana camara, Eupatorium odoratum,

Ipomea carnea and Mikania cordata have been recorded with qualitative observational effect

of these species on nearby co growing vegetation, habitat and indigenous biodiversity. The

finding of the research work can, at least help scientists throughout the country conscious of

biological invasion and can be a help of the policy makers in designing national strategy to

combat biological invasion in Bangladesh and conserve indigenous biodiversity.

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Part 2: Review of

literature

Chapter 2: Review of literature

2.1. What are Alien Invasive Species?

2.1.1. Alien Species: (synonyms: non-native, non-indigenous, foreign, exotic):

a species, subspecies, or lower taxon introduced outside its normal past or present

distribution; includes any part, gametes, seeds, eggs, or propagules of such species that

might survive and subsequently reproduce (CBD, 2001).

An alien species, also called non-native, non-indigenous, or exotic, is one that is

introduced, accidentally or purposefully, into an ecosystem in which it did not evolve.

Alien or exotic species can come from other continents, other countries and even other

parts of the subcontinent. Alien species are those that occur outside their natural range or

have established themselves accidentally or introduced deliberately (Gregorio, 2002) Non-

native plants are those that exist outside their natural range or natural zone of dispersal and

include domesticated and undomesticated species and all hybrids, except those that

naturally occur between native species (Kandasamy et al., 2003).

2.1.2. Invasive Alien Species (IAS): Various authors and organizations

defined invasive alien species differently as given below:

An “invasive alien species” is an alien species whose introduction or spread

threatens biological diversity (Ecological Society of Japan, 2002; UNEP, 2002). It can

safely be assumed that these species are invasive since they often competitively exclude

native plants (e.g. Miyawaki and Washitani, 1996; Muranaka and Washitani, 2001).

Therefore, alien plants that do not form the dominant vegetation should not be considered

as “invasive.” Propagule pressure is widely recognized as a fundamental driver of invasion

(Williamson, 1996).

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An "invasive species" is defined as a species that is 1) non-native (or alien) to the

ecosystem under consideration and 2) whose introduction causes or is likely to cause

economic or environmental harm or harm to human health. (Executive Order 13112).

Invasive species can be plants, animals, and other organisms (e.g., microbes). Human

actions are the primary means of invasive species introductions. An invasive species is a

species occurring as a result of human activities beyond its accepted normal distribution

and which threatens valued environmental, agricultural or personal resources by the

damage it cause. Invasive alien species (IAS) are those species, which have been

introduced outside their normal current or past range, and whose introduction and spread

cause harm to human health, the economy, and or the environment. They pose particular

threats to plant biodiversity and to the plant habitats on which we and millions of other

species depend for survival (Daehler and Carino, 1999).

Invasive alien species (IAS) are those species, which have been introduced outside

their normal current or past range, and whose introduction and spread cause harm to

human health, the economy and or the environment. They pose particular threats to plant

biodiversity and to the plant habitats on which we and millions of other species depend for

survival. IAS may have been introduced accidentally or intentionally, and they may be

plants, animals, fungi, bacteria, blue-green algae or viruses, IAS from all these groups are

an immense threat to the world’s plant diversity. Apart from habitat destruction, IAS are

the single biggest reason for the accelerating biodiversity crisis. Invasions of alien species

are also made worse by many of the other pressures facing the planet-habitat degradation,

climate change, urban sprawl and the impact of globalization and trade on natural

resources and biodiversity, both wild and domesticated (www.gisp.org).

Whether they are called invasive, nonnative, exotic, alien or nonindigenous,

introduced species are those that evolved elsewhere and have been purposely or

accidentally relocated. While some species have invaded habitats on their own (e.g.

migrating wildlife, plants and animals rafting on floating debris), human exploration and

colonization have dramatically increased the diversity and scale of invasions by exotic

species. Introduced species often find no natural enemies in their new habitat and therefore

spread easily and quickly (Blair, 1996).

Invasive species are ‘alien’ species whose introduction does or is likely to cause

economic or environmental harm or harm to human health”(Binggeli and Hamilton, 1993).

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Invasive alien species (IAS) are those that threaten the existence of native plants

and animals or other aspects of biodiversity, and occur in all groups of plants and animals.

The Species Survival Commission of IUCN reports that as competitors, predators,

pathogens and parasites, alien species have invaded almost every type of native

ecosystem, and caused hundreds of extinctions. Accordingly, their impacts are immense,

insidious and usually irreversible (Gregorio, 2002).

An alien species whose establishment and spread threaten ecosystems, habitats or

species with economic or environmental harm. These are addressed under Article 8(h) of

the CBD, which states that:

"Each Contracting Party shall, as far as possible and as appropriate:

...........(h) Prevent the introduction of control or eradicate those alien species which

threaten ecosystems, habitats or species."(Shine at al., 2000)

Many exotic plants are also successful colonizers of disturbances, however, and

may in turn compete with native populations (Martin et al., 2003). Many factors,

especially climate, soils and other environmental conditions can potentially influence the

number of exotic species that become established in an area. It is therefore perhaps

surprising that human population size often plays the most dominant role in determining

exotic species richness (Mckinney, 2003). Thus, predicting the ultimate impact of

disturbance requires an understanding of the differential responses of natives and exotics,

which is essential to managing, endangered plant populations in, invaded plant

communities (Mcgraw, 2003). Invasive exotic trees, especially those species that persist

during succession, may have far longer and more pronounced effects (Martin et al., 2003).

Many species of plants can crowd ecosystem, cause problems with forestation,

biodiversity conservation and have local impacts on peoples' uses of lands – yet they are

not alien invasive species. On reflection, the invasive ability of natives is not surprising.

These are plants that have proven reproductive ability within their climatic range and they

are often very able to exploit opportunities created by, say, excessive habitat disturbance

or land use change. They are often local species that respond to some changing

circumstance that makes them more obvious and deleterious to the objectives of land

management. They are usually called WEEDS - not alien invasives. A bright example of

problem native plant is cogon grass (Imperata cylindrica), a native plant of South-East

Asia, is considered as a notorious invasive species in the U.S.A. they are also useful

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wetland species that provide goods and services to people and biodiversity, while also

causing problems when they occupy new areas or increase their densities from what was

considered "normal".

2.1.3. Types of Invasive Alien Species and the ecosystem they

invade:

IAS may have been introduced accidentally or intentionally, and they may be

plants, animals, fungi, bacteria, blue-green algae or viruses (Akerson, 2003). IAS from all

these groups is an immense threat to the world’s plant diversity. Invasive Alien Species

(IAS) occur in almost every watershed and ecosystem, and represent many taxonomic

groups, including mammals, birds, reptiles, amphibians, fishes; arthropods and

crustaceans; algae, ferns and seed plants; and fungi, viruses, bacteria, and other micro-

organisms (Yan, 2003). The categories “invasive alien species,” “agricultural weeds,”

“revegetation species,” often overlap with each other, and consequently a species can

belong to more than one category (Ecological Society of Japan, 2002; UNEP, 2002).

2.2. Biological invasion is a worldwide problem

Biological invasion of ecosystem by invasive alien species (IAS) is a worldwide

problem, e.g. more than 30% of the species known from the small Indian Ocean Island of

Mauritianas are threatened with extension, principally through the effects of invasive alien

species (Sawmy, 2004). Some major culprites like Eichhornea crassipes, Pistia strateotes,

Melaleuca, Eucalyptus, Kudzu, Japanese knot weed Cogongrass (imperata cylyndrica)

etc. are major ecological problem to many countries of the world. Threat due to invasive

species on native biological diversity is increasing at an alarming rate in tropics (Allesh et

al., 2003). In South East Asia alone, according to MacKinnon (2002), IAS are causing

billions of dollars worth of damages. Invasive Alien Species (IAS) are found in all

taxonomic grounds and have affected native biota in virtually every ecosystem type on

earth. They are a major threat on a global scale and addressing IAS is of major

significance to biodiversity and sustainable livelihood outcomes. Invasive non-native plant

species are causing worldwide economic and ecological damage (Gregorio, 2002). As an

example, the State of Florida spends over 20 million dollars each year to manage just a

few of the worst problem species (Clark and Randall, 2003). Economical and ecological

losses caused by invasive species make successful control of invasions a desirable aim

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(Nehrbass et al., 2003). Next to the loss of habitats the increasing number of alien species

influences and changes worldwide native flora and fauna.

0ne of the major threats to biodiversity in the ASEAN region as well as globally is

the introduction of exotic species into the region. For the past 40 years, the rate of and

risks associated with biotic invaders have increased enormously because of human

population growth, rapid movement of people, and alteration of the environment

(Gregorio, 2002). Political boundaries are indeed porous to the intentional and

unintentional movement of species from various ecosystems in all parts of the world. And

in both ecological and economic terms, the scope and cost of biological alien invasions are

enormous (Gregorio, 2002). Although invasive alien species are a growing reality in

Bangladesh, they are still widely unnoticed by most and expanding over precious natural

resources and species.

2.3. Introduction of alien or exotic trees in the plantation

forestry of Bangladesh

Bangladesh is one of the countries to initially sign the convention on Biological

Diversity pledging to conserve the natural and biological resources. But, plantation of

woodlot in Bangladesh is antagonistic to the main premise of the convention. A big

criticism of woodlot that it is bringing in exotic species, which is damaging for bio-

diversity and when the exotic trees mature they might not prove fit for rural and wild life.

(Ammen, 1990). Teak (Tectona grandis) was the first tree introduced on hill forest

ecosystems of Bangladesh in 1871 from Myanmar (Burma). Main object of management

was and is to replace these heterogenous forests by a plantation of alien fast growing

species The rationale of clear-felling the Dipterocarp dominate natural heterogeneous

forests was that the introduced valuable timber species will be more productive than the

natural tropical wet evergreen and semi-evergreen forests (Hossain, 2004). The yield and

management of the heterogeneous forests of Bangladesh is very low and complicated.

Therefore, the need for the introduction of valuable monoculture of exotics of indigenous

or mixtures of both the species was felt at the very beginning of the scientific management

of these forests. Present day Government policy is to maximize the productivity of the

existing forests and development of new high yielding forests both on private and public

land. Introduction of fast growing exotic and multipurpose tree species both in rural and

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national forests was given priority during the 3rd 5-year Plan period (1985-90). For that

purpose, introduction of many fast growing exotic species was made. The main constraint

with these species is the collection of seeds of appropriate provenances. Exotic species

were introduced into the country without any proper documentation. Without proper

impact assessment in place, the Government had encouraged the introduction of species

with high growth rate to increase food productivity to meet the needs of the ever-

increasing population (Ameen, 1999). The most prevalent economic uses of invasive plant

species are ornamentals (40% of species), followed by erosion control (12%) and wood

production (9.5%)(Weber, 2003).

The first attempt to introduce Teak was successful in early seventies of nineteenth

century. Subsequently from 1930 and onwards, a large number of species have been tried

in different Silvicultural Research stations for searching out suitable exotics as well as

indigenous species. Out of these trials, Albizia moluccana (Acacia arabica, Anarcardium

occidentale, Dalbergia sissoo, Eucalyptus camaldulensis, Elaeis guinensis, Hevea

braziliensis, Leucaen leucocephala, Morus alba, Pinus caribaea (variety Hondurensis),

Swietenia macrophylla, Xylia dolabriformis have been successfully introduced in our

plantations (Das, 1982). Bangladesh being a member of the International Provenance

Research Programme has received a number of provenances of Pinus caribaea, Pinus

oocarpa, Tectona grandis, Albizia procera, Gmelina arborea which have been put

already in the nursery and it will go the field for provenance trials.

2.3.1. A short account of the alien and exotic trees so far introduced in

the plantation forestry of Bangladesh

From 1871 to 2005 knowledge about the forests of Bangladesh has increased in

many directions. Attempts have been made to replace the heterogeneous low yield forests

by valuable indigenous species as well as by exotic species since the beginning of the

scientific management of the forest here. Teak (Tectona grandis) was first introduced in

Bangladesh in 1871 from Myanmar (Burma). So, 1871 is the beginning point of plant

introduction of Bangladesh. Except Teak and Mahagony, the works on exotics were

organised mostly from 1930 and onwards. The exotic species, which have been

successfully introduced in the plantations, have been mentioned:

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1. Albizia moluccana Miq; Synonyms are A. falcate Backer and A. falcataria Fosbrg

a native of Moluccea was first introduced in seventies. It was planted on an experimental

basis at Lawachara in the Sylhet Forest Division. Subsequently it has been planted in

various forests areas of Bangladesh. It is a very fast growing species.

2. Acacia arabica & A. catechu: These species are the native of the drier part of the

sub-continent. Its introduction into the northern districts of Bangladesh dates back perhaps

in the nineteenth century. It is being cultivated by the farmers in the boundary of their

fields in the northern districts. A. arabica have been introduced in the late sixties in the

coastal afforestation works also.

3. Anacardium occidentale (Kaju badam); This species was first introduced in the

Chittagong Coastal areas by the Portuguese, perhaps in the later part of eighteenth century.

As a cash crop it has been introduced in Bangladesh in late fifties. The seeds were brought

from Ceylon. Its capacity to thrive in poor soils is excellent and yield of fruit is also good.

Plantation raised haphazardly is not economic at all. It needs an organised and

concentrated blocks of plantation which will be economically viable.

4. Dalbergia sissoo (Shisam): The species was introduced in this part as a roadside

tree in the northern districts. The seeds were brought from India. But now it is being

planted as a plantation species. This is being also planted in the village groves. The growth

rate is less about 1/2 Mean Annual Increment (M.A.I) over d.b.h. The growth rate here is

better than natural habitat.

5. Eucalyptus sp; Sometime in the 1930’s Eucalyptus citriodora was haphazardly

introduced into eastern Bangladesh by tea estates as an ornamental. As a forest species, it

was tried in the year 1938. This species was spread throughout Bangladesh by botanists,

foresters, gardeners and other people, but no formal plantations were developed (Davidson

and Das, 1985). First interest in other species of eucalypts was recorded in 1963 when

germination tests of three species, E. citriodora, E. tereticornis and E. botryoides were

conducted in the Silvicultural Research stations in Mymensingh and Chittagong. From

then on until 1984 about 37 species were introduced and tried . From the growth record it

appeared that it can establish in the climate and soil of Bangladesh. But, it was planted

mostly as an ornamental plant instead of forest species. It is now being also tried as forest

species.

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No attempt was made to consider Eucalyptus as a forest species till 1962. In the year

1962, seeds of Eucalyptus siderophloia, E. robusta, E. tereticornis, E. glabulus, E. rubida,

E. gigantea, E. obliqua, E. grandis, E. citriodora, E. botryoides, E. saligna, E.

camaldulensis were received from the C.S.I.R.O., Australia. Seeds were in small quantity

and were sown in the Silvicultural Research Stations at Hathazari, and Charaljani. On the

preliminary observations, it was found that E. robusta, E. tereticornis, E. glabulus, E.

rubida, E. grandis, E. saligna, E. botryoides, E. gigantea, E. citriodora can be grown.

Due to lack of subsequent persuation till 1976, no further progress was made. However, in

the meantime, Forest Research Institute, Chittagong tried few species like Eucalyptus

grandis, E. globules, E. alba, E. gigantea, etc., in the year 1969 in their campus. Here also

no subsequent persuation was made.

With the assistance of UNDP again the works on Eucalyptus species started in 1978 at

Bangladesh Forest Research Institute (BFRI). 85 seed lots of 12 species: Eucalyptus

camaldulensis, E. brassiana, E. teretocornis, E. robusta, E. saligna, E. molucana, E.

grandis, E. citriodora, E. maculata, E. acmeniodes and E. pilularis were tried in species

elimitation trial at Keochia, Hathazari, Hazarikhil, Lawachara, Charkai and Chittagong

Headquarter Stations. Out of these trials, E. camaldulensis, E. brassiana, E. citriodora, E.

robusta, and E. tereticornis have shown good growth. Eucalyptus camaldulensis has

shown over 1 MAI growth on dbh. This is the most important one out of these 5 species

tried recently. One of these 5 species, E. camaldulensis (variety petford) is being planted

in the plantations on small scale. Over 100.0 acres plantations of E. camaldulensis and E.

brassiana have been raised in different Silvicultural Research Stations. Seedlings of these

two species have also been supplied to different Forest Divisions for raising small-scale

plantations. Collection of seed is the number one problem. It is under our consideration

that we should develop our own seed sources through the seed Orchard Division.

6. Elaeis guinensis (Oil-palm): About 2 Ibs. seeds of oil-palm (E. guinensis variety

Dura) were received from Malaysia by the Silvicultural Research Division in the year

1964. It was tried at Hazarikhil and Rasulpur Silvicultural Research stations. The plants

planted at Hazarikhil started giving fruits in the year 1969. Later on, the Rubber Planting

Project also Planted some Dura variety brought from Malaysia. The fruits produced by this

plants were analysed and found that the yield of oil is comparable to those of Malaysia.

The species has gone now to plantations.

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7. Hevea braziliensis (Para rubber): The species was introduced in tea-gardens of

Bangladesh around 1910 in the districts of Sylhet and Chittagong from the seeds collected

from Calcutta Botanical Graden. Subsequently a few trees were planted at Hazarikhil

Silvicultural Research Garden. Being encouraged in 1959 from the clones brought from

Malaysia, the larger scale plantations have been undertaken by the Forest Industries

Development Corporation.

8. Leucaena leucocephala: Ipil Ipil is the common name used in the Philippines for

the exotic leguminous species Leucaena leucocephala which is also exotic to Bangladesh.

The sources of early introductions are not recorded and like many such introductions,

these have developed into a local rice. In Bangladesh, the species is frequently found in

Coastal areas where it is known as Teli Kadam (presumably because the flowers are

similar to Anthocephalus kadamba). It grows into a shrub about 15 to 20 tall. L.

leucocephala has proved itself a valuable, fast growing plantation species in the

Philippines. The timber is used for fuel-wood. The foliage provides high protein fodder for

cattle. It has also been shown to be a useful green manure crop in Hawaii and a valuable

cattle fodder in Australia. Though L. leucocephala has only been grown in Malaysia for

few years, it is already an important cattle and poultry feed. It could, therefore, be an

important species in Bangladesh where there is considerable pressure on the existing forest

for fuelwood and also for grazing land, both factors critically influence forest re-growth.

Small quantities of seed of varieties K –8 (called the “Hawaican Giant”), K –28 and K-67

were obtained from the Philippines in August 1978. These were tried at different.

Silvicultural Research stations. The results are encouraging in the plain land forests, in

homestead, on the canal and riverbanks etc. where the soil PH is over 5.5 and needs

further trial in the hill forests.

9. Pinus sp.: Pinus caribaea (from Honduras) was first tried at Hazarikhil in the year

1940. Out of these trials, two seedlings survived. These two seedlings have attained a

height of 48 and g.b.h. 32 at the age of 38 years. The second batch Pines (Pinus elliottii)

seed was collected through the Forestry Adviser, AID and the seeds were sown in the 3rd

week of November 1961. The germination was over 80%. The seedlings raised were

planted in the Forest Research Institute campus mostly. It has been found unsuitable for

our purpose. The third batch of seed was received by the D.F.O, Silvicultural Researh

Division in 1962. These include few grams of each Pinus pinaster, Pinus radiata, Pinus

thumbergii, Pinus insularis, Pinus pseudostrobus, Pinus merkusii, Pinus massociana,

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Pinus michoeana, Pinus douglansiana, Pinus montezume, Pinus caribaea, Pinus elliottii,

Pinus canariensis, Pinus ayachuta. Amongst these species, Pinus caribeae, Pinus radiata,

Pinus insularis were found to give good indication in the nursery. An acre of Pinus

radiata plantation was raised in the year 1963. Subsequently no care was taken to maintain

and no further trial was made with these species. The 4th batch of seeds was received

through the F.A.O / U.N.D.P. Project Manager in January 1970. This 4th batch included

Pinus caribeae, Pinus oocarpa, Pinus khassya, Pinus radiata and Pinus merkusii. The

seedlings were raised in polybags in the winter and were planted in July 1971 mostly in

Bangladesh Forest Research Institute (BFRI) campus. Amongst these, Pinus caribeae

(mostly Honduransis) and Pinus oocarpa have shown good growth. M.A.I. of Pinus

caribeae is near to 1 over d.b.h. estimates of yield from the in-sufficient data are highly

speculative. This projected yield comes about 25-27 m3 per hectare per year (e.g. 350-380

Cft per acre per year), but 17 m3 per hectare (240 Cft per acre) will be on the safer side. In

July 1974 Pinus caribeae and Pinus oocarpa were also planted in the F.R.I. campus,

Dariadighi, Barduara and Kaptai East Range on trial basis. About 50.0 acres of Pinus

caribeae plantations have been raised in different Silvicultural Research Stations during

the past two years from the seeds obtained through various agencies like F.A.O / U.N.D.P.

10. Swietenia macrophylla: The species was planted at Kaptai in the year 1891. The

growth is quite satisfactory. The species is now widely planted along road sides,

homestead and forest areas.

11. Xylia dolabriformis: This species was first tried at Lawachara and Hazarikhil

Silvicultural Research Stations from the seeds brought from Myanmar. Subsequently the

species was tried at Charaljani Silvicultural Reasearch Stations. The species have been

recommended for plantation in order to supply poles for the Rural Electrification Board

(REB).

2.3.2. Different stages through which the exotic species have been

passing:

2.3.2.1. Exotic species, which proved successful in trials and have already been

introduced in the plantations:

I. Tectona grandis (Myanmar and India)

II. Hevea brazilensis (Malaya)

III. Anacardium occidentale (Ceylon)

16

IV. Albizia moluccana (Not known)

V. Dalbergia sissoo (India and Pakistan)

VI. Swietenia macrophylla (Perhaps – Honduras)

VII. Acacia arabica (Not known – probably India)

VIII. Acacia catechu (Not known – probably India)

2.3.2.2. Exotic species which proved successful and have already been

recommended for introduction in the plantation:

I. Eucalyptus camaldulensis (Petford, Australia)

II. Morus indica (India and Pakistan)

III. Pinus caribaea (Hondurensis) (Honduras)

IV. Xylia dolabriformis (Myanmar)

V. Leucaena leucocephala (Philippines)

2.3.2.3. Exotics and exotic provenances which were under arboreta trials but were not

tried in plantations and now needs small-scale trial for further assessment:

I. Artocarpus fraxinlfolius (Garo Hills-Provenances)

II. Ailanthus grandis (Sadya and Assam)

III. Alurites fordii (Malaya)

IV. Alurites montanes (Malaya)

V. Alstonia scholaris (Kachar Provinances)

VI. Anogeissus acuminata wall (Central India- Provenances)

VII. Artocarpus hirsuta (W. Ghat and India)

VIII. Chcikrassia tabularis (Darang, Provenances, Assam)

IX. Calorophera excelsa (Uganda)

X. Dalbergia latifolia (India)

XI. Eucalyptus botryoides (Australia)

XII. grandis ()

XIII. robusta ()

XIV. rubida ()

XV. saligna ()

XVI. alba ()

XVII. citriodora ()

XVIII. Eugenia alba ()

XIX. Lagerstroemia hypoleuca (Andaman)

17

XX. Melia indica (Malaya-Provenances)

XXI. Pterocarpus santalinas (S. India)

XXII. Pterocarpus marsumpium ()

XXIII. Sterculia campansulata (Andaman)

XXIV. Swietenia mahagoni (Honduras)

XXV. Pinus oocarpa ()

XXVI. Pinus khasya (Thailand)

XXVII. Pinus radiata (Tanzania)

XXVIII. Pinus markusii (Thailand)

XXIX. Podocarpus nerifoliua (Kachar, Provenances, Assam)

2.3.2.4. Exotic species and exotic provenances, which were under arboreta trial

but does not require plantation trial due to their poor performances:

I. Acacia senegal (West Africa)

II. Canarium euphylum (Andamans)

III. Dipterocarpus griffithii (Burma)

IV. Eucalyptus globules (Australia)

V. maculata ()

VI. sededorophloia ()

VII. umbellate ()

VIII. Grevillea robusta ()

IX. Mangliotia insignis (Lakhshmipur)

X. Mansomia altissima (Nigeria)

XI. Michelia insignis (Tejpur, Assam)

XII. oblonga ()

XIII. clifolia (South India)

XIV. Pancevia rubignosa (Assam)

XV. Phoebe goalparansis ()

XVI. Polygala arillata (Ceylon)

XVII. Santalum album (S. India)

XVIII. Shorea assamica (Assam)

XIX. Pinus insularis (Not known)

XX. longifolia (India)

XXI. sinensis (Mauritins)

18

XXII. thumbergii (Not known)

XXIII. elliottii (U.S.A)

XXIV. Araucaria angustifolia (Not known)

XXV. cunninghamii ()

2.3.2.5. The following exotic species failed to grow due to various reasons:

I. Acacia karoo

II. cyanophylla

III. Calamus scipionum (Molucca)

IV. Populus nigra

V. wislengii

VI. trichcearpa

VII. Populus clone – 214

VIII. - 262

IX. Salix species (Willows)

X. Pinus pinaster

XI. Pseudostrobus

XII. michocana

XIII. douglansiana

XIV. montezume

XV. canariansis

XVI. ayachute

XVII. Agathis palmestromii

XVIII. Podocarpus falcatus

XIX. Taxodium spp

2.3.2.6. The following exotic species and exotic provenances are under trial in the

nursery and arboretum:

1. Gmelina arborea: Bangladesh is a member of International Provenances Trial of

Forest Tree species. Under this programme, 15 provenances of Gmelina arborea were

received from Brazil, India, Srilanka and Thailand. Seeds have been sown in the nursery.

The seedlings raised will be planted in the field during the coming planting season.

One clone of gamar received from Nigeria has also been planted in the field.

19

2. Tectona grandis: Seeds of 6 provenances of Tectona grandis from India and Thailand

have been put in the nursery. The seedlings will go to the field planting during the coming

rainy season.

3. Pinus caribeae Var: hondurensis: As a member of the International Provenance Trial

Programme, as stated earlier, provinces of Pinus caribaea were received from the

Commonwealth Forestry Institute. Out of these 7 Provenances received, 4 provenances

were from Honduras, 1 from Nicaragua, 1 from Guatemala and 1 from Belize.

4.Pinus oocarpa: Under the programme of International Provenance trial Programme,

seeds of P. oocarpa were received and seedlings have been raised for field planting. Total

8 provenances were received. These are – 3 from Nicaragua, 3 from Guatemala, 1 from

Honduras and 1 from Belize.

5.Albizia procera (Roxb.) Benth: Small quantity of seeds has been received from

Australian provenances. The seeds are being put in nursery trial (Das, 1982).

2.4. The Status of Alien or exotic Invasive plants in Bangladesh

Bangladesh has a long history of plant introduction. There are no detailed records

of exotic plants introduced in Bangladesh, except the more common plants and a few

cultivated ones. Perhaps the first widely introduced alien species in Bangladesh is Water

Hyacinth (Eichhornia crassipes), which was brought from Brazil during the British period.

British ladies were fond of its flowers and brought it over for decorative purposes. At that

time, nobody realized how vigorously this species could turn into an aquatic weed. Now it

has invaded almost all the wetlands of Bangladesh.

Many of the exotic plants are of economic benefit. Some of the very common fruit

trees, like litchi (Litchi chinensis), pineapple (Annas sativus), watermelon (Citrullus

lantus), coconut (Cocos nucifera) and guava (Psidium spp.) are also introduced, as are

most of the pulses and oil yielding plants. Many important vegetables, like cucurbits

(Cucurbita spp.), radish (Raphanus sativus), potato (Solanum tuberosum) and carrot

(Daucus carota) came from other countries and have been naturalized throughout the

country (Islam, 1991). In the 19th century, the British Foresters were mostly contributed to

the introduction of economically important forest trees (Tectona grandis, Paraserianthes

falcataria, Henea brassiliensis, Xylia kerrii, Swietenia macrophylla, S. mahagoni) from

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almost all the continents. The same trend of introducing species continued and 20th century

and some Australian (Eucalyptus camaldulensis, Acacia auriculiformis, A mangium) and

South American species (Leucaena leucocephala, Pinus caribaea, P. oocarpa) are getting

preferences in plantation forestry. More than 100 tree species were tried in the forest

plantations of Bangladesh, of which only about 15 species are successful in plantation

programs (Hossain, 2004).

The main trees recommended for woodlot are Eucalyptus camaldulensis, Acacia

Mangium and Acacia auriculaeformis. In neighboring countries like India, Thailand

criticism against Eucalyptus is very strong and in India the angry villagers have reported

to have felled Eucalyptus from vast areas. The deliberate biasness of planting exotic

invasive already has changed the species rich natural forests to mono plantations of some

invasive species. Some of the species are aggressively occupying the natural ecosystems

and replacing the native vegetations.

The deliberate biasness of planting exotic invasive already has changed the species

rich natural forests to mono plantations of some invasive species. Some of the species are

aggressively occupying the natural ecosystems and replacing the native vegetations. The

ecologists, foresters, policy makers and environmentalists became concerned about the

loss of native biodiversity along with the deterioration of soil properties due to the

establishment of plantations with introduced species (Hossain, 2004). Scientific studies

show that indigenous species and even mono-culture of Sal found to have been more

productive and economic than the mono-culture of alien exotic species (Chowdhury ,

2003).

However, a good number of exotic plants are weedy in nature. Most of them were

first introduced as garden or ornamental plants before becoming established elsewhere.

Some of them are so well established that they are now the dominant plant and became

noxious weeds of forests and wastelands (Eupatorium odoratum, Mikenia cordata, Croton

spp. etc.). some are also considered noxious weeds of cultivated fields (Alternanthera,

Scoparia and Heliotropium spp.). Others are found in water (Eichhornia, Eleocharis and

Monocharia spp) (Ameen, 1999)

Uddin and Mohammad (2003) described a total of 113 plant species have been

identified as invasive those introduced here in Bangladesh by intentionally, accidentally,

purposely or by vectors. These are assigned into six categories including timber yielding,

fruits bearing, vegetable producing, flowers bearing, avenue tree, and weeds. Hossain and

21

Pasha (2001) prepared a short list of the alien invasive plants that are threatening the

ecosystem of Bangladesh which is given below:

Table 1: Some Alien exotics in Bangladesh, which have a detrimental impact in the

ecosystem:

Scientific Name Family Origin Impact on the ecosystem

Acacia

auriculiformis

Mimosaceae Australia Widelyplanted in afforestation

programs,butcontroversy over

pollen allergy!

Eucalyptus

camaldulensis

Myrtaceae Australia Promising growth

performance in experimental

plantations, but now ban due

to its controversial impact on

environment.

Leucaena

leucocephala

Mimosaceae Tropical

America

Occasionally cultivated; wild

in coastal areas; suppressed

the regeneration of other

species.

Acanthospermum

hispidum

Asteraceae South

America

Common weed of cultivated

fields

Cassia occidentalis

L.

Caesalpiniaceae Tropical

America

Common weed for wasteland

and road side

Cestrum diurnum L. Solanaceae Tropical

America

Weed of road side and rail

line

Lantana camara L. Verbanaceae Tropical

America

Common weed of hilly areas,

prevent regeneration of native

species

Ageratum

conyzoides L.

Asteraceae South

America

Common weed of waste and

cultivated field; aeroallergic

pollen species

Alternanthera

flocoidea L. R.Br.

Amaranthaceae Brazil Common weed of cultivated

and waste land

Atylosia

scarabaeoides

Benth.

Fabaceae Australia Common weed of wasteland

Eupatorium Asteraceae Central

South

Common weed of wasteland;

suppressed the regeneration of

22

odoratum L. America other species in plantation

programs

Commeline oblique

Buch-Ham.

Commelinaceae Java Frequent weed in wasteland

Convolvulus

arvensis L.

Convolvulaceae Europe Frequent weed of waste place

Croton

bonplandianum

Baill.

Euphorbiaceae South

America

Abundant weed of waste and

cultivated land

Eichormia crassipes

(C. Martius) Solms.

Pontederiaceae Tropical

America

Abundant aquatic weed;

aggressive growth inhabits

other aquatic flora

Evolvulus

nummularius L.

Convolvulaceae West India Common weed in cultivated

and open fields.

Hyptis suaveolens L.

Poit.

Lamiaceae Tropical

America

Common weed of hilly

regions

Ipomoea carnea

Jacq.

Convolvulaceae America Common weed of all habitat

Ludwigia

adscendens L.

Onagraceae Central

America

Common weeds in aquatic

and marshy habitat

Mikenia cordata

(Burm. f.) Robinson

Asteraceae Tropical

America

Abundant weed of forest and

wasteland; engulf other

economic crops by its

luxuriant growth

Mimosa pudica L. Mimosaceae South

America

Common weed of cultivated

and waste land

2.5. Alien Invasive Plant Species in the Global Context

2.5.1. Alien Invasive Plants in Europe: Europe appears to have less

invasive plant species but is the source of many invaders elsewhere (Weber and Peter,

2003). Fallopia japonica (Houtt.) Ronse Decr and F. sachalinensis (Schm.) Ronse Decr as

well as their hybrid F. x bohemica (Chrtek et Chrtkova) J. P. Bailey native to East-Asia

belong to the most dangerous invasive alien plants in Europe. Impatiens glandulifera,

Robinia pseudoacacia also causing harm to environment (Balogh and John, 2003).

23

In central Europe IAS are considered to be of lower ecological risk compared to

other regions. Of the 3383 established species of higher plants in Germany, About 30 of

the around 1000 neophyte plant species are considered to have negative impacts on native

biodiversity (Frank, 2004).

Environment obligation to eliminate invasive alien species in Slovakia applies

only to the seven most problematic plant species: Fallopia japonica, Fallopia x bohemica,

Fallopia sachalinensis, Heracleum mantegazzianum, Impatiens glangulifera, Solidago

canadensis and Solidago gigantean (Ema and Alzbeta, 2004).

Only four species orgroups present over 50% of all reported cases (Heracleum

mategazzianum, Fallopia spp, Solidago gigantea and S. canadensis). There are only a few

variations in the species mentioned. Prunus serotina and Rosa rugosa are especially

mentioned in the North of Germany, and Acer negando in the East

2.5.2. Alien Invasive Plant in North America: Invasives in the United

States included Canada thistle (Cirsium arvense), musk thistle (Carduus nutans), spotted

knapweed (Centaurea stoebe ssp. micranthos), diffuse knapweed (Centaurea diffusa),

yellow starthistle (Centaurea solstitialis), Russian knapweed (Acroptilon repens),

hawkweed (Hieracium sp), purple loosestrife (Lythrum salicaria), leafy spurge

(Euphorbia esula), Dalmatian toadflax (Linaria dalmatica), perennial pepperweed

(Lepidium latifolium), sericea lespedeza (Lespedeza cuneata), downy brome (Bromus

tectorum), medusahead (Taeniatherum caput-medusa), saltcedar (Tamarix spp.) and

tropical soda apple (Solanum viarum) (Duncan et al., 2003).

2.5.3. Invasive Alien species in South America (Brazil): Brazil is the

largest country in South America and it holds nearly 20% of the planet’s biodiversity, as

well as the largest percentage of freshwater species. Certain species which have a clear

history of invasion in other parts of the world and which have proved to become far more

of a problem than a solution, are currently being promoted in Brazil. The best example

may be Azadirachta indica (neem), a species widely invasive throughout West Africa,

recognized by farmers as a threat to economic sustainability. Neem is currently “the

species of the moment” in North Eastern Brazil, where the dry climate of the Caatinga is a

restriction to non-native species. Neem has been so successfully promoted that by now

nearly every rural property has a few trees planted for producing “natural herbicides” for

crops and medicinal substances.

24

Common invasive plant species are: Eragrostis plana, Ulexeuropaeus, Pinus

elliottii and Pinus taeda, especially in Southern grasslands; African grasses in the genus

Brachiaria all over the country and covering large extensions of central savannas;

Hedychium coronarium (white ginger), Artocarpus heterophyllus (jackfruit), Acacia

mangium, Elaeis guineensis (oil palm) in the Atlantic Forest; Hovenia dulcis (Japanese

cherry), Eriobotrya japonica (loquat), Melia azedarach (china berry), Ligustrum lucidum,

L. japonicum (tree privet) and Mangifera indica (mango) in riparian areas in the North

east. Species currently promoted for bio-diesel production are Ricinus communis (castor

bean) and Elaeis guineensis (oil palm), possibly characterizing the “ecological” production

of fuel as an environmental problem (Silvia, 2004).

2.5.4. Invasive Alien Species in South East Asia (SEA): Invasive alien

species (IAS) are causing billions of dollars worth of damage in Southeast Asia (SEA) as

well as causing displacement and, in some cases, extinction of hundreds of indigenous

species. Yet despite the magnitude of the damage, the prominence given to the control of

IAS in the Convention of Biological Diversity and the many international protocols and

initiatives to tackle this issue, almost no attention is paid to this threat in SEA; there are

few national programmes to combat established IAS or reduce the risk of more from

becoming introduced. Equally shocking is the fact that whilst some species have become

established accidentally, the bulk was deliberately introduced. The data sheets held on

SEA countries by the Global Invasive Species Programme database (Allan, 1936). for

instance fail to reflect the great extent or urgency of the problem. Hundreds of species are

involved - not less than ten species per country documented in the database.

In Malaysia, certain foreign species like itch grass (Rottboella cochinchinensis

Lour); water hyacinth (Eichhornia crassipes Martius); aquarium watermoss (Salving

molesta Mitchell) are officially listed by the country’s regulatory agencies as dangerous

exotic species as these are potential threats to agriculture (plants, crops, animals, live-

stock), non-cultivated ecological systems and human beings once these species enter and

establish themselves in the country.

In Philippines, Hagonoy weed (Chromolaena odorata) Large leaf lantana ihinese

creeper (Mikania micranth) Gmelina arborea, Acacia mangium, Eucalyptus

camaldulensis, Swiietenia macrophylla, Dipterocarpus grandiflorus, Leucaena

leucocephala, Toona ciliata, Water fern (Salvinia molesta), Water hyacinth (Eichormia

crassipes) etc. are doing great loss to ecosystem.

25

Of the 100 world’s worst IAS listed by the Invasive Species Specialist Groups

(ISSG), at least, 1 aquatic plant, 13 land plants, exists in Thailand. Some of the more

important IAS identified are water hyacinth (Eichornia crassipes) and giant water fern

(Salving molesta) among the water weeds, and gaint sensitive plant (Mimosa pigra), Siam

weed (Chromolaena odorata), mila-a-minute (Mikania micrantha), and Maui pamakani

(Ageratina adenophora) among the terrestrial weeds.

Some major culprits: Among the worst IAS in the ASEAN region are the: water

hyacinth (Eichhornia crassipes), pantropical weeds (Imperata cylindrica), Chinese

super-tree (Paulownia tomentosa) (Gregorio, 2002). Almost all lakes and fresh waterways

of the region are clogged with such species as water hyacinth (Eichhornia crassipes),

water lettuce (Pistia stratiotes), and yellow burhead (Limnocharis flava). These species

impede boat transport and fishing activities and also cause eutrophiation and loss of

productivity. Clearing these weeds annually involves great labour costs.

In addition to many pantropical weeds that have become very aggressive such as

Eupatorium (Chromolaena) odoratum, Mimosa pudica and grasses like Imperata

cylindrica, many ornamental plants are spreading out of control across the region. These

include. Lantana camara, Caesalpinia pulcherrima and climbing plants that can smother

the original vegetation such as Blue Trumpet Vine (Thunbergia grandiflora), Morning

glory (1pomea cornea), 1pomea cairica, Mile-aminute vine (Mikania micrantha),

Bougainvillea spectabilis and the edible Thai vine (Coccinea indica). Exotic coloniser

shrubs such as Piper aduncum, Mimosa pigra and prickly pear (Opunia monacontha) now

cover huge areas of the region (Mackinnon, 2002).

Foresters have consistently introduced exotic trees for plantations. There is often a

short-term advantage in planting a species in the place where its natural pests and diseases

are absent. In some cases such species spread out of control, displacing natural vegetation

and profoundly changing the natural ecology (Mackinnon, 2002). The Chinese super-tree

(Paulownia tomentosa) is listed as invasive in many countries. Several introduced conifers

have become established in the region and the spread of Australian Eucalyptus and Acacia

has a profound effect. Both Acacia auriculiformis and Acacia mangium grow well in SEA

(e.g. Bangladesh, India, Pakistan, Philippines, Thailand etc.) and spread naturally over

cleared and burned areas. These species create conditions of great flammability and

themselves thrive on regular fire episodes in lands where natural forest fires were unheard

of. As the 'haze' fires now burn annually in Borneo and Sumatra, so do these species

26

spread at the expense of native species and transform those islands into firescape monsoon

forests (Mackinnon, 2002).

2.6. 100 of the world’s worst invasive alien species:

(Listed by the Invasive Species Specialist Groups (ISSG) of IUCN (2003).

AQUATIC PLANT

Caulerpa seaweed (Caulerpa taxtfolia)

Common cord-grass (Spartina anglica)

Wakame seaweed (Undaria pinnatifida)

Water hyacinth (Eichhornia crassipes)

LAND PLANT

African tulip tree (Spathodea campanulata)

Black wattle (Acacia mearnsii)

Brazilian pepper tree (Schinus terebinthifolius)

Cogon grass (Imperata cylindrica)

Cluster pine (Pinus pinaster)

Erect pricklypear (Opuntia stricta)

Fire tree (Myrica faya)

Giant reed (Arundo donax)

Gorse (Ulex europaeus)

Hiptage (Hiptage benghalensis)

Japanese knotweed (Fallopia japonica)

Kahili ginger (Hedychium gardnerianum)

Koster’s curse (Clidemia hirta)

Kudzu (Pueraria lobata)

Lantana (Lantana camara)

Leafy spurge (Euphorbia esula)

Leucaena (Leucaena leucocephala)

Melaleuca (Melaleuca quinquenervia)

Mesquite (Prosopis glandulosa)

Miconia (Miconia calvescens)

Mile-a-minute weed (Mikania micrantha)

Mimosa (Mimosa pigra)

Privet (Ligustrum robustum)

Pumpwood (Cecropia peltata)

Purple loosestrife (Lythrum salicaria)

Quinine tree (Cinchona pubescens)

Shoebutton ardisia (Ardisia elliptica)

Siam weed (Chromolaena odorata)

Strawberry guava (Psidium cattleianum)

Tamarisk (Tamarix ramosissima)

Wedelia (Wedelia trilobata)

Yellow Himalayan raspberry (Rubus ellipticus)

MICRO-ORGANISM

Avian malaria (Plasmodium relictum)

Banana bunchy (Banana bunchy top virus)

27

Chestnut blight (Cryphoneotria parasitica)

Crayfish plague (Aphanomyces astaci)

Dutch elm disease (Ophiostoma ulmi)

Frog chytrid fungus (Batrachochytrium dendrobatidis)

Phytophthora root rot (Phytophthora cinnamomi)

Rinderpest virus (Rinderpest virus)

AQUATIC INVERTEBRATE

Chinese mitten crab (Eriocheir siensis)

Comb jelly (Mnemiopsis leidyi)

Golden apple snail (Pomacea canaliculata)

Green crab (Carcinus maenas)

Marine clam (Potamocorbula amurensis)

Mediterranean mussel (Mytilus galloprovincialis)

Northern Pacific seastar (Asterias amurensis)

Fishhook flea (Cercopagis pengoi)

Zebra mussel (Dreissena polymorpha)

LAND INVERTEBRATE

Argentine ant (Linepithema humile)

Asian longhorned beetle (Anoplophora)

Asian tiger mosquito (Aedes albopictus)

Bigheaded ant (Pheidole megacephala)

Common malaria mosquito (Anopheles quadrimaculatus)

Common wasp (Vespula vulgaris)

Crazy ant (Anoplolepis gracilipes)

Cypress aphid (Cinara cupressi)

Flatworm (Platydemus manokwari)

Formosan subterranean termite (Coptotermes formosanus shiraki)

Giant African snail (Achatina fulica)

Gypsy moth (Lymantria dispar)

Khapra beetle (Trogoderma granarium)

Little fire ant (Wasmannia auropunctata)

Red imported fire ant (Solenopsis invicta)

Rosy wolf snail (Euglandina rosea)

Sweet potato whitefly (Bemisia tabaci)

AMPHIBIAN

Bullfrog (Rana catesbeiana)

Cane toad (Bufo marinus)

Caribbean tree frog (Eleutherodactylus coqui)

FISH

Brown trout (Salmo trutta)

Carp (Cyprinus carpio)

Large-mouth bass (Micropterus salmoides)

Mozambique tilapia (Oreochromis mossambicus)

Nile perch (Lates niloticus)

Rainbow uout (Oncorhynchus mykiss)

Walking catfish (Clarias batrachus)

Western mosquito fish (Gambusia affinis)

28

BIRD

Indian myna bird (Acridotheres tristis)

Red-vented bulbul (Pycnonotus cater)

Starling (Sturnus vulgaris)

REPTILE

Brown tree snake (Boiga irregularis)

Red-eared slider (Trachemys scripta)

MAMMAL

Brushtail possum (Trichosurus vulpecula)

Domestic cat (Felis catus)

Goat (Capra hircus)

Grey squirrel (Sciurus carolinensis)

Macaque monkey (Macaca fascicularis)

Mouse (Mus musculus)

Nutria (Myocastor coypus)

Pig (Sus scrofa)

Rabbit (Oryctolagus cumiculus)

Red deer (Cervus elaphus)

Red fox (Vulpes vulpes)

Ship rat (Rattus rattus)

Small Indian mongoose (Herpestes javanicus)

Stoat (Mustela erminea)

Chapter 3: Of the attributes of

invasive plants

3.1. What are the negative impacts of invasive plants? /What

Threats Do Invasive Species Impose to ecosystem?

Biological invasions have caused severe unwanted impacts to local environments

and economics (Gollasch, 2004). Biological invasion has been becoming one of the most

serious problems in environmental protection and economic development (Zhang, 2004).

Invasive exotics rank second only to habitat destruction as a threat to rare and endangered

species. Yet competitive interactions between invasive and rare plants are often poorly

understood, with few data available to direct management (Thomson, 2003).

The significant impact of invasive alien species (IAS) to biodiversity has been

widely acknowledged (IUCN, 2000), yet little has been done to link IAS management with

29

biodiversity conservation, especially from an on ground perspective (Mahon 2000;

Downey 2003a). Reasons for this failure may be attributed to: (i) IAS management has not

been aligned with available information on alien species impacts to biodiversity (Mahon,

2000); (ii) information on the species directly impacted by each IAS is inadequate

(Downey 2004); (iii) the legislative requirements for alien species are listed under several

Acts, while others are not listed under any Acts (Downey 2003a); and (iv) the separate

historical management approaches of these two disciplines (Saunders et al. 1995; Downey

2003a).

The invasive alien species are mainly causing three different types of damage.

They are: 1) Damage to ecosystems, 2) Damage to human safety, 3) Damage to

agriculture, forestry and fisheries (Toshikazu, 2004).

The causes and impacts of increasing invasive species abundance are complex and

of interdisciplinary nature, involving ecological, social, and economic issues, and

interactions between them. The spatiotemporal distribution and composition of

biodiversity, and local forest resources in general, can be affected directly by invasive

species due to predation, herbivory, parasitism, pathogens, and competition (Poulsen, 2004).

Invasions by both native and exotic species potentially can threaten natural

communities. Invasive species contribute directly to the decline of threatened and

endangered plants and animals. Only habitat loss poses a greater threat. Invasive

species also exact heavy costs in lost productivity (Anon, 2003).

Second only to habitat destruction, invasive species pose the most significant threat

to native biodiversity worldwide. Invasive species have many devastating environmental

effects, including predation upon native species, unfettered population growth due to lack

of natural predators, and competition with indigenous species for scarce resources. Once

introduced, invasive species are difficult, if not impossible, to eradicate and may cause

extensive economic as well as environmental damage (Courtney and Perkins, 2004).

Biological invasion can permanently change ecosystems but methods for constraining

most invasions are unknown (Wilson, 2003). Species invasions are hypothesized to occur

in a series of steps, beginning with initial immigration of individuals to a new site.

Following an establishment period, the population begins to spread in an uncontrolled

manner and replace native species (Stanton et al., 2003).

Invasive species introduced by human being whether intentionally or

unintentionally create serious threats to biodiversity by replacement or predating of native

30

species. Invasive species also bring many threats to agriculture, fisheries and forestry and

help to spread communicable diseases (Makiko and Nobuo, 2004).Invasive and exotic

species may negatively affect a community by leading to decreases in population numbers,

increases in species extinctions, or altering ecosystem function (Mooney and Drake 1986;

Vitousek et al., 1996). The effects may be brought about by several factors, including

increased competition pressures, predation, disease, or amensalism (Martin and George, 2003).

Invasive species is an increasingly important disturbance factor throughout the

world’s humid tropical forests, affecting the spatial and temporal distribution and

composition of plants and animals. This change the availability of non-timber-forest

products to people who live, and depend upon resources found in, forests. Indigenous

people living in more interior parts of the forest away from developed infrastructure, and

hence often having few or no alternative income sources or options, will therefore tend to

be more sensitive to changes in the availability of local natural resources.

Although the number of invasive weeds is small, the costs are huge to the economy

and to the environment (Anon, 2003). Invasive weeds strive towards a monoculture,

choking out all desirable species (Vollmer and Jennifer, 2003). Invasive plants made

alteration of fundamental ecosystem structures and processes. Invasive plant species are

recognized to be a severe threat to environmental sustainability altering biogeochemical

cycles and disturbance regimes (Ustin et al., 2003). Mass invasions of alien plants (Plants

form the biological foundation of all terrestrial and aquatic communities) more or less

cause structural and functional changes in ecosystems, including alterations in nutrients

and/or structural conditions (Schmitiz et al., 1997). When an invasive plant species has

characteristics quantitatively different from those of species indigenous to the invaded

community, it has a great potential to alter ecosystem properties (Symstad, 2003). Many of

the invasive species have severely affected existing natural systems by displacing or

competing with native species and altering native habitats, or by damaging agro

ecosystems and other human resources (Andreasen, 2001). Particularly, changes in

dominant plant species may lead to the replacement of dominant plant consumers,

followed by their predators, and further cause a chain of changes in species compositions

at every trophic level, and thus disrupt food webs and other structural and functional

features of the ecosystem. In some cases, such ecosystem changes induced by an invasive

species can be perpetuated by a positive feedback cycle not dependent on the invader. In

31

these circumstances, eradication of the invasive species will not be sufficient to restore the

invaded community to its pre-invasion state (Symstad, 2003).

Even if the invasive species are pioneers dominating only early phases of the

vegetation succession were, the effects of the invasion may last long through persistent

soil seed bands. Invasive alien plant species, when once established in an ecosystem, may

cause irreversible changes by producing large seed sources above and/or under the soil

surface. (Thompson, 2000). Contemporary surface soils of various habitats, including

wetlands, woodlands, plantations, floodplains and farmlands have more or less

accumulated viable seeds of such alien plant species, even if the above-ground vegetation

contains no or few alien plant species. Flourishing invasive alien plants furnished with

strategies enhancing spatial and temporal dispersal of seeds inevitably cause alteration of

the earl stages of succession series. This is likely to be one of the most conspicuous

influences of plant invasions on ecosystem processes. Once a persistent soil seed bank of

an invasive species has been established, either natural or human disturbances will always

ring about the domination of the alien species, which will further replenish the soil seed

bank or enlarge the seed sources of the invasive species

Invasive species may negatively impact native species in any number of ways

including: competing with them, mating with them and decreasing genetic diversity,

introducing pathogens and parasites that sicken or kill them, and -disrupting available

nutrients. Art introduced species can change the look and makeup of an entire

system-changing species composition, decreasing rare species, and even changing or

degrading the normal functioning of the system. Maintaining intact natural systems is

important to ensure the continuation of ecosystem goods and services upon which humans

depend. Invasive plants can smother native vegetation or change the timing and severity of

fires, floods, and other disturbances. Introduced diseases and parasites can attack and

eliminate dominant native plant species.

In forestry and agricultural production, invasive plants outcompete crops for soil

and water resources, reduce crop quality, interfere with harvesting operations, and reduce

land values. The U.S. Department of Agriculture estimates the annual productivity loss of

64 crops due to exotic species at $7.4 billion. On rangelands, invasive plants, such as

Ageratum conyzoides, Eupatorium odoratum, crowd out more desirable and nutritious

forage, cause soil erosion, and poison some wildlife and livestock species. In natural areas,

nonnative plants, such as Eucalyptus camaldulensis reduce habitat for native and

32

endangered species, create fire hazards and interfere with recreational activities. Aquatic

invasive species, such as the Eichhornia crassipes clogs lakes and waterways and

adversely affect fisheries, public water supplies, irrigation, water treatment systems,

recreational activities, and shipping. In 'the ocean, nonnative marine organisms are now

impacting the availability of energy (Khanna, 2003)

Throughout the humid tropics, highest concentrations of native and endemic

biodiversity tend to occur in the interior of forests, which also tend to be critical for the

livelihoods of many indigenous peoples. Invasive species change the utilization (such as

extraction) patterns of local forest resources. Finally, there may be a feedback impact of

the changed spatiotemporal utilization patterns on the distribution and composition of the

natural resources (Poulsen, 2004).

Invasive alien species represent a major disruption for all biotic systems including

terrestrial and aquatic, managed and wild. Invaders can have enormous economic and

human health impacts as well as degrading many system properties that society values,

including biodiversity. Invasive species can devalue the ecosystem services upon which

we all depend in all nations, developed and developing (Harold, 2001).

Invasive species cause ecological damage by outcompeting native species,

reducing biological diversity, and changing ecosystem functions such as flood and fire

regimes or nutrient cycling. The Asian vine Mikania quickly climbs over trees and shrubs

and even kill them by strangling and shading. Invasive species also have major economic

consequences, ranging from the loss of economically valuable species to the costs of

controlling or managing infestations on public lands.

3.1.1. Harold (2001) summarized negative impacts of invasive plants as follows:

Invasive can disrupt community and ecosystem processes

Invasives are causing large economic losses and are threats to human health and

welfare and to sustainable development

Invasive alien species have altered evolutionary trajectories

Losses to agriculture, forestry and fishery

Increased maintenance costs for roadways

Damage to waterways and rivers

33

Alien species that are health hazards

Endangerment of native species.

3.2. The scale of economic losses by invasive plants

The spread of invasive alien species may have an economic or ecological impact.

For example, In total, the enumerated costs for these species and add up to an average

annual expenditure of € 167 million in Germany, and are estimated to cost $ 137 billion

annually in losses to agriculture, forestry, fisheries and the maintenance of open

waterways in the United States alone (Anon, 2003). These losses are seen in production

losses in agriculture, forestry, and fishery, and costly eradication programmes to eliminate

undesirable species (Money and Hobbs, 2000). Similar costing exercises are almost totally

absent in the South East Asian(SEA) region. But given the size of the region, the total

human population and the greater direct dependence of the population on biodiversity and

primary production systems, it is clear that the damage to ecosystems and economies must

also be counted in billions of U.S dollars per annum (Mackinnon, 2002). But the economic

or ecological loss of invasive alien species are not quantified in Bangladesh.

3.3. The traits of successful invaders

Invasive species often exhibit certain characteristics: they spread aggressively,

reproduce quickly, have short juvenile periods, tolerate a wide range of climatic conditions

and habitats, compete efficiently against other species, and thrive in disturbed areas

(Rahel, 2002). These alien invasive plants are able to reproduce rapidly because the

animals and diseases that keep them in check in their home ranges are missing (Drees,

2003). For example, Teak (Tectona grandis) trees from Myanmar threaten to replace the

ground vegetation. When the populations of native plants are reduced, the animals that

depend upon them lack the food and shelter needed for survival (Drees, 2003). Species

with fast reproductive rates and good dispersal ability are very dangerous. Such species

include many grasses, climbers, coloniser shrubs and trees with wind dispersed seeds.

Introduction of close relatives of indigenous species is highly prone to result in genetic

pollution of the local form (Mackinnon, 2002).

34

3.3.1. We are facing a great challenge of the invasives because:

Invaders are self replicating

Evolve response to control efforts Invasive, invasive plants and animals in

particular, can quickly

Lag times are common before adverse effects are seen

Invaders alter and respond to community interactions in complex ways

Movement of potential invasive material is increasing

Global changes mostly favor invasives

Informations base inadequate for risk assessment

Inadequate public awareness of the problem (Harold, 2001).

3.4. What makes a community invisible?

Understanding plant community susceptibility to invasion is important to

implement invasive plant management. Determining susceptibility may be achieved

through study of the invasive plant species distribution and growth along environmental

gradients (Prather et al., 2003). The notion of assembly rules lies at the heart of predictive

community ecology and the prediction of successful invasion of communities by non-

native species is an important goal for forest managers. Neutral (null) models of

community assembly, as well as drift models (Hubbell) suggest that all communities

should be equally invasible and that good invaders are mainly good dispersers. Niche-

based assembly theory would suggest another set of answers. First, invasible communities

(i.e. “open” communities) should be those that are constrained by weak assembly rules

(e.g. places of maximum species density) or they are communities that do not conform

closely to the local assembly rules (e.g. places that are chronically disturbed or places

where the natural processes have been altered for a protracted period of time). Second,

species that have good dispersal ability and establishment ability tend to be good invaders,

but these species are only rarely labeled “invasive” because they rarely dominate

communities. In order to dominate. invasive species must also have high rates of resource

acquisition and have strong competitive effects on neighbors. Invasive species with very

high competitive ability may simply be a replacement for a native dominant species and

35

this may make the question of community invisibility moot. The most difficult question

for understanding species invasiveness is how dispersal, establishment, and competitive

effect are enhanced upon introduction. Escape from co-evolved microbial and fungal

pathogens as well as parasites and predators, must be critical for prolonged invasiveness

(Weiher, 2004).

Examining patterns of invasion allows us to make some generaIisations. Some

ecosystems are more vulnerable than others. Freshwater systems, Small Island, areas with

high number of local endemic species and areas undergoing major landcover

transformation are particularly vulnerable and need special vigilance and protection. A

logged forest is more prone to invasion than a primary forest (Mackinnon, 2002)

Invasions of alien species are also made worse by many of the other pressures

facing the planet — habitat degradation, climate change, urban sprawl, and the impact of

globalization and trade on natural resources and biodiversity, both wild and domesticated

3.5. Process of biological invasion of the ecosystem

Biological invasion is an irreversible process. Contaminated chemical in the

environment will be decomposed after several years, however invaded organisms

reproduce themselves and persist almost for ever. New invading organisms will change the

nature of forests, rivers and lakes in the future.

The process of biological invasion is complicated, involving many interacting

factors related to the invader, the vector, and the source and recipient ecosystems.

However, an invasion can be conveniently broken down into three phases: arrival,

establishment, and ecological integration. A successful invader, however, must be

accomplished at each. Examination of the worldwide invasion of Musculista senhousia

also emphasizes several topics of general importance to invasion biology. First, prolonged

time lags might exist at each stage of the invasion process, making prediction difficult.

Second, the factors that make ecosystems vulnerable to invasion are typically difficult

identify, and are often confounded with the supply of potential invaders to the system.

However, experimental approaches can offer some insight into the problem of invisibility.

Third, some of the most profound effects of invaders result from the physical modification

of habitats, and certain classes of these impacts may in fact have a relatively high degree

of predictability (Crooks, 2004).

36

3.6. Mechanisms of habitat degradation due to invaders

Harold (2001) presented the mechanisms of habitat degradation due to invaders.

For most invasive alien species it is not difficult to demonstrate negative impact. By

illustrating the great number of ways in which an invasive alien species can threaten the

goods and services provided by natural systems upon which society depends. This list

includes species that are:

Fire stimulators and cycle disruptors;

Water depleters;

Disease causers;

Crop decimators;

Forest destroyers;

Fisheries disruptors;

Impeders of navigation;

Clogger of water works;

Destroyer of homes and gardens;

Grazing land destroyers, Species eliminators;

Noise polluters and Modifiers of evolution

3.7. Invasive Weeds

We are all affected by weeds. Weeds are simply plants that grow where they are

not wanted. Invasive weeds are plants that must be managed intensively or they will

overgrow crops or completely take over natural ecosystems. Weeds are invasive plants

that degrade our natural areas, reduce the sustainability of our agricultural industries and

affect the health of people and animals. Plants provide us with food and fibre, decorate our

yards and gardens, and provide habitat for wildlife. But when plants grow where they are

not wanted, we call them weeds. To homeowners, weeds may be unwanted plants in lawns

or gardens. To farmers, weeds are plants that interfere with raising crops or livestock. To

37

biologists who manage natural areas, weeds are plants that interfere with the functions of

natural communities.

Natural area weeds are often exotic plant species (plants whose natural range does

not include Bangladesh and were brought here from outside the country that have become

naturalized (capable of reproducing outside of cultivation). Invasive exotic plants are

weeds that alter the functions and value of natural areas by displacing native species and

disrupting natural processes such as fire and water flow (Rahel, 2002). Some invasive

weeds like Mimosa pudica Eupatorium odoratum L., Lantana camara L., Croton

bonplandianum Baill., Atylosia scarabaeoides Benth., Ludwigia adscendens (L.) ,Mikenia

cordata, Alternanthera flocoidea etc. are creating major problem to our forests and

wastelands. Foresters must remove invasive exotic plants species to maintain the integrity

on natural areas:

3.7.1. Weeds can:

Cause allergies and sickness.

Poison and injure domestic pets and livestock.

Increase the cost of food.

Block and pollute waterways, affecting the quality of our drinking water and

increasing the cost of its management.

Reduce the productivity of crops and pastures.

Increase the risk of herbicide resistance in agriculture.

Increase the risk of bushfire.

Harbour feral animals and diseases.

Reduce biodiversity and contribute to local extinctions of native plants and

animals.

Spoil our natural landscapes and reduce their appeal to tourists.

Affect our recreational use of natural areas

3.7.2. Invasive weeds share several common traits:

o Grow fast and spread across large areas,

38

o Reproduce several ways including seeds, buds, fragments, and shoots from

roots,

o Survive in many different temperature, light, water and soil conditions,

o Difficult to control, and nearly impossible to eradicate (Anon, 2003). Pasture

grass species are a major source of plant invaders in many parts of the world

(Heywood, 1989; Lonsdale, 1994). It is not surprising, therefore, that these

plants, which were chosen because of their rapid growth, adaptation to sunlit

environments, and tenacity, have also shown markedly high invasiveness

(Washitani, 2002a; Myers & Bazely, 2003).

3.8. Invasive Aquatic plant problem

Plants grow in a variety of different forms. Some are emergent plants, some are

floating plants and others submersed plants. Aquatic plants that evolve or develop in one

geographic area or region are said to be native aquatic plant to that area. Native aquatic

plants are a natural part of lakes, rivers, and wetlands and play several important roles in

maintaining healthy aquatic ecosystems. Native aquatic plants seldom cause problems

because they have adapted to one another and their environments over millions of year.

Invasion by non-native species is a serious threat to the conservation of freshwater

ecosystems (Fuller et al., 1999; Rahel, 2002). Aquatic plants that are moved, either on

purpose or by accident, to other areas are called non-native, non-indigenous, exotic or

alien aquatic plants. People move plants from one location to another for many reasons

including food for themselves and for livestock, or because of the plant’s unusual or

beautiful appearance (Anon, 2003).

Many different insects and diseases evolved with and control native plants,

keeping them from becoming problems. The delicate balance among native plants is often

destroyed when people introduce fast growing invasive aquatic weeds from other areas

without the controls that keep them in check in their home waters.

3.8.1. Native aquatic plant benefits include:

o Shelter for fish, birds and other wildlife,

o Habitat for insects that are eaten by fish,

o Protect shorelines from erosion,

39

o Clean some pollution from water.

3.8.2. On the other hand Invasive aquatic weeds:

o Destroy fish and wildlife habitat,

o Block navigation and flood control,

o Stop recreation like swimming and fishing,

o Reduce tourism and properly values,

o Clog drinking, irrigation and hydroelectric power and pipes

(Anon, 2003).

Biological invasion into aquatic systems causes, in some occasions, drastic

changes and serious impacts to native ecosystems. Oceanic islands are in general much

more susceptible to invasions than continents (Philip and Lloyd, 2001). Dispersal vectors

of aquatic invasions are shipping (ballast water and hull fouling), intentional releases for

fisheries, aquaculture and recreational fishing, and uninterntional introduction with the

target species. The new convention for the control and management of ballast water and

sediment was adopted at the diplomatic conference of International Maritime Organization

(IMO) in February 2004, and legislative management of introduced marine organisms is

now being developed in each ratifying country. However, methods for the risk assessment

and management for other vectors have never been developed effectively (Keiji and

Katsuki, 2004).

In comparison with unvegetated systems, the early stage of non-indigenous aquatic

weed infestation in lakes and reservoirs appears to provide some environmental or

ecological benefits. Unfortunately, short-term habitat and water quality gains are often

followed by long-term management as well as ecological problems (Smart et al., 2003).

The aquatic environment provides unique opportunities for invasive species and

challenges for resource managers. The combination of an open niche and the usual

presence of numerous nonindigenous species in the watershed often result in serious

management problems when nonindigenous aquatic plants invade (Howard, 2003).

Unfortunately, it is often difficult to establish aquatic plants in unvegetated

systems. Fluctuating water levels, high levels of nutrients and turbidity, and the presence

of omnivores such as common carp and turtles can be serious impediments to

establishment of diverse native plant communities (Smart, 2003).

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3.9. Invasive Alien species in wetlands in Bangladesh

Wetlands in Bangladesh are increasingly being recognized as ecosystems of

extreme importance to man and biodiversity. People derive many benefits from the goods

and services provided by wetlands while wetland systems are the “homes” of many

species of animals and plants and their habitats.

Wetlands, as well as lakes and rivers, however, has been impacted by alien

invasive species that specialize on aquatic (and semi-aquatic) systems and which cause

damage to their human benefits and their biodiversity. These are species that come from

“outside” and which arrive without their native controls – such as their own competitors,

predators, parasites and pathogens. They are species which grow fast, spread quickly and

cause all manner of problems in their “new” ecosystems.

The damage caused by alien invasive species to Bangladesh wetlands runs into the

billions of dollars annually – but hard data is hard to acquire as the impacts of these

species are only just being realized. Most well-known would be the Water Hyacinth -

sometimes called “the world’s worst water weed” – which has inflicted wetlands, lakes,

rivers hydro-schemes, irrigation and water supply systems, fisheries and human welfare -

not to mention its effects on Bangladesh’s aquatic biodiversity. There are the huge costs of

control, to manage the invasive species and then to try restoring the affected ecosystems to

their previous condition.

Bangladesh’s wetlands and then the threats they pose in existing and future

invasions. It is also necessary to provide some information on their identify, possibilities

for control and sources of available information and technical assistance. Wetland

invaders can rarely be eradicated, but they can usually be controlled if efforts to prevent

their arrival have failed and if they have become established. Control is always expensive

and time-consuming but can result in lasting ecosystem integrity.

3.10. Exotic invasive plants in the hill forest of Bangladesh

Exotic invasive plant species are threatening world forests through the alteration

of plant community composition. As a result, forest regeneration and understory diversity

may be restricted or greatly reduced (Ross and Joan ,2003). Bangladesh, like many other

41

countries have a long history of plant introduction from different geographic areas of the

world. A good number exotic plant became weedly in nature. Most of them were first

introduced as garden or ornamental plants and mainly brought by settlers, invaders,

seamen and traders. Some of them are so well established that they are now the dominant

plant and became noxious weeds of forests and wastelands. Some of the species, namely

Ageratum conyzoides, Eupatorium odoratum, Hyptis suaveolensis, Lantana camara and

Mikenia cordata have luxuriant growth and suppressed the regeneration and growth of

other native valuable species. This results low productivity and loss of native floral

diversity of the hill forests areas of the country. Infestation of these aggressive plants is

expanding and posed threat to natural habitats and plantation forests. The possible

suggestions to prevent the impacts of invasive plant species are enhancing awareness

among the planters, growers and publics; development of a database on invasive species,

quantify the abundance of the species, development of an environmentally sound

eradication methods and also introducing the necessary quarantine, legislation and

regulations on the spreads of the invasive plants (Hossain, 2003).

3.11. invasive plants in Sunderbans mangrove forest

Sunderbans is the world’s largest continuous single block of mangrove forest. Its

rich blend of flora, fauna and vivid ecosystem function make it a unique ecosystem in the

world. Over the few years the forest is under severe human disturbance. These are

basically changed in the salinity regime, introduction of terrestrial species in the

mangroves, construction of dams and illicit feling. All these leads introduction of few

alien species at the same time several native species to become invasive. Among the exotic

species Echhornia crassipes, Eupatorium odoratum, Micania scandens, Syzygium

fruticosum are causing enormous damage to the Sunderbans ecosystem. On the other hand,

Derris trifoliate, Acrosticum aureum, though known widely as mangrove associates, now

affecting the ecosystem badly. Initially these species does not seems problematic but as

human disturbance increase, so as their rate of invasion also increase. A study was

conducted through a combination of systematic and purposive sampling to identify their

impact on the Sunderbans. It was appeared that these species affect the Sunderbans

ecosystem from very initial stage of ecosystem dynamics. Echhornia crassipes,

Acrosticum aureum impedes the mangrove propagule restricting propagule movement also

impedes mangroves normal expansion. Derris trifoliate twist the host tree. Syzygium

42

fruticosum initially was limited only within open raised area of Sunderbans but the species

has coped to stay with the saline environment and densely colonizes inside the forest floor.

In newly formed land these species with their profuse regeneration colonizes and restricts

mangrove settlements. The ecological associations of these species were also identified.

Monitoring of rate of invasion with abundance was suggested for determination of

ecosystem health hazards caused by invasive plants (Biswas, 2003).

3.12. Invasive Alien Plant Species in Riparian Areas

Invasion by alien plants constitutes one of the most serious threats to biodiversity

through the displacement of native plants (Coblentz, 1990; Vitousek et al., 1996;

Simberloff et al., 1997). Owing to frequent disturbance, riparian areas are particularly

vulnerable to invasion by alien vascular plants (Stohlgren et al., 1998; Hood & Naiman,

2000). Riparian ecosystems are important for maintaining local biodiversity because of

their environmental uniqueness. Riparian vegetation is established under the influences of

unique environmental conditions such as flooding disturbance regimes. The vegetation

thus established in turn influences the dynamics of water flow and the movement of

sediments and nutrients into rivers (e. g., Peterjohn & Correll, 1984; Decamps, 1993) and

it features high species diversity (Gould & Walker, 1997). One explanation for the high

species diversity of riparian ecosystems is that floods periodically destroy vegetation

cover, create bare ground for recolonization, and produce a shifting mosaic of vegetation

patterns and landforms that create diverse habitats (Hood & Naiman, 2000). In addition,

riparian areas serve as landscape corridors facilitating the dispersal of propagules by water

flow, which is indispensable to range expansion and maintenance of metapopulation

dynamics of riparian plants. (Campbell et al., 2002).

The same factors that maintain a diversity of plant species may equally increase

vulnerability to invasion by alien plants in riparian areas (Washitani, 2000). Disturbances

to create unoccupied sites and dispersal of propagules by water flow in riparian areas may

promote invasions by alien plant species for some of the same reasons that they sustain

native species diversity.

The availability of suitable habitats and the supply of propagules of alien

agricultural weeds and revegetation species in riparian areas may account for their

invasiveness. As we already mentioned, riparian habitats are subject to increase the

43

creation of bare areas suitable for colonization by these species. (Pollock et al., 1998).

Although the terrestrial habitats of riparian areas are diverse, the aquatic environment is

relatively uniform (Ashton & Mitchell, 1989). Accordingly, many species, particularly

submerged and floating plants, are widely distributed throughout the world. This holds for

alien aquatic plant species such as water hyacinth (Eichhornia crassipes (Mart.) water

lettuce (Pistia stratiotes L.) Red water fern (Azolla filiculoides) water fern (Salvinia

molesta) etc. (Committee for Investigating the Effects of and Countermeasures against

riparian exotic Species, 2003).

In riparian areas, propagule supply from adjacent invaded habitats (e.g., Pastures,

revegetated levees, agricultural fields, roadsides) is likely to contribute significantly to the

further invasion of alien plants. More than half of riparian invaders are agricultural weeds,

so appropriate management of weeds in agricultural areas could be effective in restricting

the introduction of new invaders to riparian areas. Most weeds of agricultural systems

have competitive ruderal adaptations that are suitable for taking over disturbed habitats

(Grime, 1977). Consequently, environments favoring these species include sparse

meadows that are subject to seasonal disturbances such as floods, as well as roadsides and

agricultural fields. These characteristics of agricultural weeds make them potential

invaders of riparian habitats. Therefore, alien plant management plans are needed for both

natural habitats and agricultural areas. In addition, the use of alien pasture species for the

purpose of revegegetation or control of soil erosion should be restrained, firstly to

conserve biodiversity and native ecosystems, but also to avoid provoking grass pollen

allergies. Identifying the characteristics of invasive alien species is the first step in

developing management strategies for riparian areas and will be a stepping-stone to further

detailed studies on invasion biology and conservation ecology.

3.13. Atmospheric invasion by pollens of non-native plants

Most research on plant invasion impacts focus on the effects of weeds on crops or

the effect of well established introduced species on community structure or ecosystem

functioning. However, quantitative information regarding the risk they pose for human

health is anecdotal.

One of such risks can be the allergenic nature of the pollen of some introduced

plants. The pollen spectrum contains 95 pollen taxa. Even though pollen from native taxa

44

is more diverse than pollen from non-native taxa, that it is present in the atmosphere for a

longer period of time. Most of the airborne pollen is allergenic. Non-native pollen has a

larger proportion of allergenic pollen than native pollen. Most of this non-native pollen is

allergenic. The presence of non-native airborne pollen enlarges the period of allergenic

symptoms susceptibility (Vila and Jordina, 2003).

Invasive species like Melaleuca in limited plantation in Bangladesh is blamed to

spread pollen allergy.

3.14. Ways of spread of invasive plants or the vectors of

invasives

Today, many species, either intentionally or accidentally, have been introduced

into sites that were not their original habitats (Primack and Kobori, 1997). Some

nonnative species have been deliberately introduced in Bangladesh. More than 300 exotic

species are supposed to either wildly growing or cultivated as an economic crop in

Bangladesh. Of them the herbaceous and lianas are the dominant exotics followed by trees

and shrubs.

Introduction of invasive alien plants may be intentional or unintentional.

"Intentional introduction" means an introduction made deliberately by humans, involving

the purposeful movement of a species outside of its natural range and dispersal potential

(Such introductions may be authorized or unauthorized). Intentional introduction may be

by Institutions (FD, BFRI etc.) setters, invaders, seamen and traders. Most of the plants

have been brought by Institutions (FD, BFRI etc.) settlers, invaders, seamen and traders.

"Unintentional introduction" means an unintended introduction made as a result of a

species utilizing humans or human delivery systems as vectors for dispersal outside its

natural range. Unintentional introduction may follow natural process.

The distributions of many species are restricted by factors such as climate,

environmental conditions, and geographic limitations. However, humankind has

considerably changed the process of natural evolution by relocating countless species of

plants. Invasive species can move among and across continents in a number of ways,

Identifying and understanding those pathways can suggest ways to slow or stop the

movement (Reichard S. H. 2003).

45

Increased and more efficient worldwide trade, travel, and transport is greatly

increasing the number and diversity of harmful organisms being moved around the world,

as well as the rate at which they are moving. Expanding global trade in agriculture,

forestry, fisheries and other industries that depend on raw materials has allowed the

transport of species to various parts of the world. This has provided wider access to the

world’s biodiversity, thus providing better opportunities for economic and social

enrichment. One of the most significant impacts of the globalisation of trade has been the

establishment of non- native species that have wreaked havoc on local ecosystems.

Imported agricultural materials are principal source of exotic weed seeds (Makiko and

Nobuo, 2004).

Human activities have increased the wholesale movement, either accidental or

deliberate, of many species of plants and animals from one region of the planet to another.

Human activities have improved the odds for many non-indigenous species. A rapidly

increasing human population has led to greater land disturbance, which favors the spread

of invasive species. Increased demands for food and fiber and overuse of public lands for

recreation and commercial purposes have also contributed to nonnative invasions.

Invading species have often been able to establish populations in the new regions, many

spreading successfully over large areas or achieving high abundances (Andreasen, 2001).

Good invaders are mainly good dispersers (Weiher, 2004).

Some agricultural crops and trees have escaped plantations and became pests and

the importation of agricultural and forestry products have brought assorted pest species

and diseases into new areas. Nonnative ornamental plants are used in landscaping around

homes and institutions. Many have moved into natural landscapes, some with significant

ecological or economic impacts.

The aquarium trade is the source of a large number of aquatic species accidentally

or Intentionally released into waterways. Aquaculture has also increased the spread of fish

and other aquatic species and associated diseases.

The expansion of international distribution associated with globalization of

economy has caused increase of biological invasion (Koich et al., 2004). At the same time,

human- driven changes in land use and climate are rendering some habitats more

susceptible to invasion.

46

Thousands of species of marine organisms were and are moved around the world

on ship bottoms, and hundreds more have been moved globally by the wholesale transfer

of edible oysters, for "replanting."

Ships’ ballast water is known as one of the primary vectors of un-intentional

species introductions in aquatic ecosystems. Shipping, i.e. ballast water and hull fouling, is

the most important vector of un-intentional species introductions in aquatic ecosystems

(Gollasch, 2004). It is estimated that more than 10,000 marine species each day may hitch

rides around the globe in the ballast water of cargo ships. When ships unload their cargo,

they often fill their ballast tanks with water to provide balance for their return journey. In

addition to water, marry aquatic organisms are sucked into these tanks and given transport.

A ship will then empty its ballast tank (and various aquatic stowaways) at the next port it

takes on cargo. Many invasive species have become introduced into new areas this way.

Flooding can also transport nonnative aquatic and marsh species to row regions.

Species invasions are one of the top four anthropogenic threats of the worlds oceans

(Gollasch, 2004).

Fragmentation of habitat may be important factor to determine spread of invasive

plants. Habitats of plants are usually fragmented to some extent. Sparse habitat patch

density may cause delay in spatial spread of invading plants, and sometimes prevent

invasion if habitat patch density is low enough (Koike, 2003). Knowledge of the

ecological constraints on an invading species is essential for predicting its potential

distribution and can reinforce the justification for removing isolated populations beyond

the main invasion front (Pattison and Richard, 2003).

3.15. Invasive Alien Plants may not show signs of invasion

through years

The impacts on biodiversity and ecosystem functioning, caused by invasive alien

species (IAS), are often more surprising or more complex than the impacts of agricultural

weeds, for example. Indirect impacts on native species can also be surprising. An

established alien species may be “dormant” and show no signs of being invasive for years

or decades, before rapidly expanding in range and abundance and becoming invasive

(Crooks and Soule 1999, Mack et al., 2000). Triggers can include changes in ecological

conditions- human disturbance, or even natural disturbances like hurricanes. Another

47

reason why it may take time for invasiveness to show up is that it may require cumulative

interactions with other alien species. Not only can interactions with other alien species

trigger invasiveness in previously non-invasive species, it can also create a risk that an

already invasive species might become even more invasive (McNeely et al., 2001).

Of course, many if not most, alien species will not become invasive. But given that

the impacts from alien species can be direct, indirect, cumulative and/or complex,

unexpected, surprising and counter-intuitive and that they often only show after

considerable lag times, any alien species must be considered “guilty” until proven

“innocent”, where the risk of becoming invasive is concerned. This has also been

expressed by IUCN and GISP respectively as: “In the context of alien species, unless there

is a reasonable likelihood that an introduction will be harmless, it should be treated as

likely to be harmful” (IUCN, 2000). Or every alien species needs to be managed as if it is

potentially invasive, until convincing evidence indicates that it presents no such threat”

(McNeely et al., 2001)

3.16. Attributes of the invasiveness (invasibility) of a non-native plant

species

To determine which characteristics contribute to the invasiveness of a species and to

the invisibility of an ecosystem, Milbau and Ivan (2003) conducted experiments with

simulated invasion in synthesized grassland communities. The results suggested that

species characteristics would largely determine the possible extent of an invasion event

(number of seedlings), while the final success of the individual invaders (growth and

survival) is determined by both species and ecosystem characteristics. They therefore

argued that invasion success depends on a match between invader characteristics and

habitat, and that life-history traits themselves are not a significant predictor. Their second

experiment showed that on a small scale invasion resistance was higher in more diverse

communities. Both invader and leaf length decreased with increasing species number,

while invader germination was unaffected. Differences in invisibility could be partly

explained by the increasing biomass of the plants surrounding the invaders and the

decreasing amount of photosynthetically active radiation (PAR) reaching the invader

seedlings in the more diverse communities.

48

Weber and Nicole (2003) forwarded a key question towards predicting the invasion

ability of plant species is, whether invasive species have characters that distinguish them

from closely related non-invasive species. Their experiment demonstrated that plant size is

the most pronounced difference between invasive and non-invasive congeners, and that

relative growth rates as well as amount of phenotypic plasticity are not necessarily

correlated to invasion success.

Successful invasion may depend on the capacity of a species to adapt to a spatially

varying environment. Local adaptation is usually considered to result from the interplay

between natural selection (which increases locally favoured genes) and gene flow (which

introduces foreign maladapted genes) (Alleaume -Benharira et al., 2003). A nitrogen-

fixing species can increase nitrogen levels, change nitrogen-cycling in the ecosystem and

potentially facilitate the further invasion of other exotic species (Van Riper and Jennifer,

2003).

3.17. Biological invasion and ecological resistance

The term, ecological resistance was first coined by Elton in the 1950’s to describe

those processes or system properties that reduced the likelihood of an invader establishing

and having an impact in a community. Over the following decades, ecological theory

developed primarily around the assumption that competition was the key structuring force

in natural communities and was the likely source of resistance to invasion for species

introduced to communities where they were previously absent. However quantitative

evaluations of resistance have shown that it can result from competition,

predation/herbivory or from abiotic factors, these factors vary over space and time and that

resistance is therefore probabilistic and variable (D’antonio, 2003).

3.18. Effect of climate change on the success of invasive plant

species

Biological invasions and climate change are two of the greatest environmental

challenges that we face today. Individually, each of these elements of global change is the

subject of much research. However, studies of invasion biology have rarely considered

climate change, and vice versa. Such research is important because biological invasions

can have strong effects on the structure and function of ecosystems that are responding to

49

a changing climate and on the services provided by those ecosystems; climate change is

also altering the context in which potentially invasive species succeed or fail. There are a

variety of reasons why climate change might be expected to increase the success of

biological invaders. For instance, a rapidly changing climate might favor species that can

extend their ranges quickly or that can tolerate a wide range of climatic conditions. Both

of these traits are shared by many invasive plant species. Few studies have focused on the

general mechanisms through which climate change could benefit invasive species. How

much climate change will benefit invasive species remains difficult to predict and will

always be difficult to measure. Hopefully, results from future research will teach us how

to minimize the benefits that invasive species might draw from a changing climate (Dukes,

2003).

3.19. Restoration of soils altered by exotic plant invasions

The potential for restoring soils affected by exotic plant invasions is not well

known, in part because the kinds of changes that occur following invasions are not yet

well characterized. Ehrenfeld (2003) described the changes that have been documented in

upland soils, following invasions of Japanese stilt grass (Microstegium vimineum). Include

the loss of the organic horizon, an increase in soil pH, altered patterns of nitrogen cycling

and availability and changes in microbial community structure. These results suggest that

the restoration of forest soils may require reductions in both pH and N availability,

alterations that are opposite to the most common manipulations in soil restoration of

degraded sites. Methods for such soil manipulations are not well developed, and so there

are few well-known tools to accomplish such changes. The manipulations that have been

used to decrease soil pH and N availability are likely to be effective only over short time-

periods, suggesting that long-term restoration requires identification of the mechanistic

link that allows an exotic to cause the alteration to begin with. Long-term restoration

strategies should include the introduction or re-introduction of native species whose effect

on the target soil process is opposite to that caused by the invasive species. Methods for

manipulating the soil biota to produce long-term, stable changes in both the microbiota

and the fauna are particularly poorly known (Ehrenfeld, 2003).

50

3.20. Hybridization and evolution of invasiveness in plants

Ellstrand et al., (2003) presented and review a remarkable number of cases in

which hybridization occurred prior to the appearance of the emergence of successful

invasive populations. Hybridization between species or between disparate source

populations may serve as a stimulus for the evolution of invasiveness. Progeny with a

history of hybridization may enjoy one or more potential genetic benefits relative to their

progenitors. The observed lag times and multiple introductions that seem a prerequisite for

certain species to evolve invasiveness may be a correlate of the time necessary for

previously isolated populations to come into contact and for hybridization to occur.

3.21.Biological invasions in protected areas

Invasive species are largely seen as a problem by virtue of their devastating effects

in high conservation value areas (Akerson, 2003). Protected areas (PAs) form the last

remnants of less degraded landscapes and ecosystems around the world. Invasive alien

species (IAS) are frequently cultivated and intentionally dispersed in protected areas for a

variety of reasons. Considering the formally protected areas such as national parks, which

are more commonly assured of legal protection from habitat fragmentation, invasion may

become the greatest threat to many protected areas.

Macdonald et al (1989) showed that the increase in number of visitors to a reserve

leads to an increase in the number of introduced plants species. This is probably due to the

importation of propagules by the visitors themselves, or by attaching to vehicles. If the

hypothesis that an increase in tourism will lead to an increase in biological invasions holds

true, the short-term benefits of increased revenue will place an ever-increasing demand on

resources in the long-term. Macdonald et al. (1989) also indicate that habitat modification

leads to an increase in alien plant species, through building of roads, campgrounds and

other facilities.

Many forest managers simply cannot identify many of the invading alien species

(Macdonald, 1991) and rely on a few organizational experts to cover vast areas. In

practical senses, this is simply not possible and rangers, game guards, tour guides and

others staff (and suitably trained volunteers), that are operating in the field on a daily basis

need to be responsible for detecting and reporting invasions (Pauchard & Alaback, 2004).

As with many other aspects of PA management, fences and other artificial

boundaries are ecologically meaningless. Protected areas, even those of millions of

51

hectares, are islands and need to adopt an approach that is outward looking and considers

the broader physical and social environment. Examples of invasive species causing

damage in PAs are numerous in the terrestrial, freshwater and marine environments and

invasive alien species have been a major concern for PA managers (Howard, 2003).

3.22. Risk assessment of invasive plants

This refers to an approach that seeks to identify the relevant risks associated with a

proposed introduction and to assess each of those risks. Assessing risk means looking at

the size and nature of the potential adverse effects of a proposed introduction as well as

the likelihood of them happening. It should identify effective means to reduce the risks

and examine alternatives to the proposed introduction. The proposed importer often does a

risk assessment as a requirement by the decision-making authority (Shine et al., 2000).

Risk assessment associated with invasive weed species has to date focused

primarily on assessing the risk of invasion and/or establishment in uninfested areas. It is

suggested that this approach is relevant only to those species with limited or unknown

local distributions (Sing and Robert ,2003). The majority of managed invasive weeds fall

outside of this category. Weed management options included in a variety of environmental

impact assessments generally list no treatment within reviewed strategies. However,

quantitative or even qualitative evidence of invasive species impacts seldom support the

stated outcome (Sing and Robert ,2003).Before introducing any plant into Bangladesh

from any country, assessment of the possible risk of ecosustem damage should be

assessed. Othrewise society must pay the damage in terms of mass ecological damage of

the country.

3.23. Justification of planting only native trees in afforestation/ reforestation/

landscape plantings

Native plants are believed to be superior to introduced species because of their

better growth, reduced likelihood to become invasive, their indirect and direct biodiversity

value and their contribution to local sense of place. In all cases there are exceptions where

non-native species play an important role. Interest in landscaping with native plants has

grown rapidly in recent decades, but there is also a rise in ‘native only’ policies where

52

attempts are made to exclude introduced and exotic species from landscape schemes

(Kendle and Forbes, 1997). There are five common arguments that are forwarded

concerning the importance of native plants and the dangers of introduced aliens or exotic

species (Hitchmough and Dunnett, 1996; Gilbert and Anderson, 1998).

1. Natives grow better, or are more hardly or disease resistant than exotics:

Simple observation and common experience quickly refute this argument. What it is

always possible to find instance where poorly chosen exotics perform badly, agronomists,

foresters and horticulturists have shown over centuries that many of them can grow

outside of their place of origin without problems. At sub-specific level a lot of work on

‘provenance’ of seed source has been done by foresters. Whilst again it is possible to find

comparisons where locally adapted provenances outperform imported stock (Jones and

Evans, 1994) there are also examples where the opposite is true (Lines, 1987).

Not only can non-natives grow well, and not only are we dependent on many of

them for food, shelter, cloths etc. but some can perform functions that ultimately benefit

native species, such as the use of soil-building species in derelict land reclamation. These

potential benefits are reviewed by Williams (1997) who argues that possible functional

benefits of non-natives in natural habitats include:

Structural diversification and niche creation

Food supply

Facilitation of regenerations of natives (nurse species)

Modification of disturbance (e.g. reducing erosion or fires)

Directly compensating for the loss of a native that was important

for ecosystem function.

It is true that many exotic species are not so well adapted as to form reproducing and self-

sustaining populations out of their range, but that is actually one of their advantages in

many land use situations as they are unlikely to become weeds.

2. Exotics are likely to become invasive and out complete natives: Whilst being

identified as less well adapted to our climate than natives, exotics are simultaneously

expected to grow much better and to become invasive weeds (e.g. Gilbert and Anderson,

1998). Invasiveness is of course a serious problem and weed invasions are causing havoc

in habitats worldwide. An extensive range of legislation and policy necessarily underpins

international and national attempts to control the spread of potentially damaging species,

but for this to be effective it is important for implementation to be well focused. The

53

greatest source of confusion is that it is false to attribute the risk of invasion to aliens

alone.

Despite frequent implied association in the literature, invasiveness and exotic

status are not really closely correlated. Most aliens in the Bangladesh are not exotic weeds,

whilst some natives are. The term ‘invasive’ should only be applied to alien species, whilst

for native we should use the less pejorative term ‘expanding’, which is more like semantic

politics than an objective assessment. On reflection, the invasive ability of natives is not

surprising. These are plants that have proven reproductive ability within their climatic

range and they are often very able to exploit opportunities created by, say, excessive

habitat disturbance or land use change. In many cases in landscape work it is, therefore,

the very absence of reproductive capability in exotic species, which obviously cannot be

guaranteed for natives, that makes them so useful. If exotics have any unique capability to

be weeds, it is because out of those that can reproduce, some of them may lack local pests

or pathogens that would put constraints of their reproductive ability. However, the

disappearance of constraints can also happen to natives, for example, if a major predator

goes through a population decline). Sometimes existing but rare indigenous species can

become weeds because of change in land management (Garrott et al., 1993

3. Native support many more associated species than exotic species: It is known

that there is a close relationship between native plants and co-adapted feeding

invertebrates. As a general rule the longer a plant has been established within a region’s

flora the number of associated species that have adapted to feed on it (this process is

ongoing – nature allows for new arrivals even if some scientists do not). It need not hold

true for all circumstances or for other forms of plant-animal and plant-plant relations. For

example:

Non-natives can carry a high biomass of those invertebrates that they do support,

thereby fuelling a food chain (Gilbert, 1989). This may be because they lack some

of the defenses against invertebrate feeding that would be shown by the co-adapted

native plants.

Non-natives may have beneficial structural effects within a habit, such as

providing shelter for over-wintering birds or habitats for lower plants (Harding and

Rose, 1986).

They may produce animal food at times when the native flora does not.

54

Non-natives may be able to survive in unusual circumstances where the native

flora will find it difficult.

The range of associated species may not be able to colonize all habitats or all life

stages of the natives they are associated with. Conversely for most of our

introduced species we have never explored the invertebrate list that they may

support if allowed to become veteran trees in ancient woods in the countryside. So

on balance, natives do often support more feeding invertebrates, but this does not

merit an assumption that the conservation value of non-natives is negligible.

4. Native genetic diversity needs to be protected as part of the world’s store of

biodiversity: It is unquestionable that native plants represent each country’s own slice of

the world’s genetic diversity and there is a local responsibility to protect them. It is,

however, worth balancing this point with a recognition that form a global representative

non-natives may represent a resource of genetic diversity that has been lost or suffered

massive depletion in its country of origin. One example is the Bermuda Cedar (Jumiperus

bermudiana), which is a self-regenerating timber tree in St Helena but is a threatened

species in Bermuda. Lugo (1997) tells a similar story with Delonix regia, naturalized and

common in Puerto Rico, and in danger of extinction in its country of origin, Madagascar.

Increasingly conservationists will be faced with situations where a species’ original habitat

has become unsuitable because of environmental change, and deliberate translocation

outside of its former range in the only option (Davis, 1989). Similarly where there is only

a constrained vulnerable population, extension outside of the native range may be seen as

an important insurance strategy (Maunder, 1992).

In many cases different native ecotypes, and even native species, freely interbreed

to produce hybrids (Cousens, 1963) but the process of environmental selection continue to

operate and usually re-establish genetic boundaries. In fact this hybridization is an

important evolutionary process and the hybrids can sometimes directly support a greater

range diversity than when species are kept pure (Whitham et al. 1999). They often

accumulate the invertebrate taxa of both parents, rather than exclude them. Some

additional invertebrates depend on the hybrids. This seems to be because the hybrids often

show less resistence to exploitation by associated biota, such as invertebrates, than

resistant pure species do (Whitham et al. 1999). For artificially inbred populations

breaking up gene complexes may lead to better adapted individuals than the parents are

(Fenster and Dudash, 1994).

55

5. Native plants are regionally appropriate and define our landscape character:

The concept of regionally appropriate vegetation clearly has importance. Plants do help to

define the landscape character of an area. However, once again it does not follow that

native plants are always the most appropriate and it certainly does not follow that non-

natives do not have a place. The pine forests of Scotland (Pinus sylvestris) are a

fundamental part of the atmosphere and character of the region, but many would feel that

the landscape of Breckland, East Anglia in England would also be compromised if lost

the introduced shelter-belts of the same tree (Brown, 1997).

We appreciate plants for their diversity, interest, beauty and geographical and

cultural histories rather than condemning them because they ‘did not originate here’. This

perspective opens doors to ethnic groups, by recognizing the positive side of the urban mix

and providing opportunities for dialogue to begin. More fundamentally it also remains all

of us that protection of local nature is just a tactic in the wider issue of protecting global

nature.

Ending remark: The above functional critique of the importance of native plants in

the landscape amounts mostly to an illustration of how, in a complex environment super-

imposed with equally complex human history, culture, values and aspirations, it is

impossible to characterize one group of plants as ‘superior’ than others. This is especially

true when the classification system is as nebulous and as value-laden as our definition of

native. In essence it is clear that all of the arguments given to favour the use of native

plants in the landscape contain truths, but they can never be always true and they cannot

all be acted on. So in the conclusion, are native-only policies justified? Of course not.

They are often better, and we would subscribe to the argument that local character and

local species should always be given a presumption in their favour when planting

anything, but this is not the same as endorsing condemnation of alternatives or ‘arbitrary

discrimination against exotic species’ (Brown, 1997).

Chapter 4: Instruments dealing

with IAS

It is increasingly apparent that international cooperation is essential for the

prevention, eradication and control of invasive alien species (IAS). This has been formally

56

recognized by the UN Convention on Biological Diversity (CBD) and in various other

international forums. Various other organizations dealing with IAS has been given below:

4.1. The Global Invasive Species Database (GISD):

The Global Invasive Species Database (GISD) is primarily a management

information and awareness-raising tool. A database was compiled comprising of plant

species that are currently viewed as highly invasive in natural habitats in various regions

of the world. The basis for the plant list was an extensive literature search and information

available from the Internet. The database includes 814 plant species and each species was

complemented by ecological and geographic features such as life form, geographic

distribution, family, and economic uses. It has a focus on geographic and information gaps

so that more of the world’s communities can have access to relevant information (Browne

and Maj, 2003). The database was analyzed with regard to taxonomic patterns of invasive

plant species, patterns of economic uses and whether there are differences among life

forms with regard to their geographic distribution and economic uses. The most prevalent

life forms were perennial herbs, followed by treesand shrubs.

The Global Invasive Species Database (GISD) provides a broad audience with easy access

to authoritative information on IAS. It disseminates globally sourced information,

including good practice, case studies, specialist’s knowledge and experience. The database

has a dual aim: to raise awareness about invasive alien species, their impacts, and the

opportunities to fight back; and to be a management tool assisting decision makers,

practitioners and communities to address their IAS problems. Now the GISD contains

profiles of more than 250 species that threaten biodiversity, ranging from microorganisms

to plants and animals. Future plants include ongoing population of the database with more

profiles and development of a CD-ROM version of the database for those who have poor,

or no access to the Internet, -bridging the digital divide (Weber, 2003).

4.2. Global Invasive Species Program (GISP)

The need for concerted global action to combat IAS has led to the creation of the

Global Invasive Species Programme (GISP). The Programme was established in 1 997 to

address the global threats caused by IAS and to provide support to the implementation of

Article 8(h) of the Convention on Biological Diversity (CBD). GISP is operated by a

consortium of the Scientific Commiftee on Problems of the Environment (SCOPE), CAB

57

International (CABI), and the IUCN-World Conservation Union in partnership with the

United Nations Environment Programme (UNEP).

In essence, GISP aims to conserve biodiversity and sustain human livelihoods by

minimising the spread and impact of IAS. To realise this mission, GISP operates through a

“Partnership Network” comprised of scientific and technical experts on IAS issues from

around the world. GISP stakeholders are its Partners-governments, intergovernmental

organisations, non-governmental organisations, academic institutions, and the private

sectorThe Global Invasive Species Programme (GISP) has been instrumental in

encouraging international scientific collaboration to improve understanding of IAS, their

impacts and their management.

4.3. Other organizations working with IAS

Aside from the GISP numerous international instruments have been developed to

deal with IAS. The most comprehensive is the 1993 Convention on Biological Diversity,

which calls on its parties to “prevent the introduction of, control or eradicate those alien

species which threaten ecosystems, habitats or species” Article 8h). The World

Conservation Union (IUCN), through its Invasive Species Specialist Group, has also

worked to raise international awareness of IAS issues, through its network of experts and

its list server, newsletter and database. Several international initiatives against invasive

species are now underway or planned, under the auspices of GISP and with the

involvement of IUCN and other organizations (Clout, 2003). Another is the 1952

International Plant Protection Convention (IPPC), which applies primarily to plant pests,

based on a system of phytosanitary certificates. The IPPC was extensively revised in 1997

to meet some of the new challenges of plant pests.

The International Maritime Organization (IMO) has also been working on ways to

prevent the spread of marine alien organisms in ballast water and sediments since the mid-

1970s. In 1997, the IMO Assembly adopted Guidelines for the Control and Management

of Ships’ Ballast Water to Minimize the Transfer of Harmful Aquatic Organisms and

Pathogens. The Guidelines are intended to assist Governments and appropriate authorities,

ship masters, operators and owners, and port authorities, as well as other interested parties,

in minimising the risks through ships entering their ports, but call for this issue of

worldwide concern to be addressed through action based on g\lobally applicable

regulations.

58

Table 2: A partial list of international instruments dealing with IAS

Cartagena Protocol on Biosafety to the Convention on Biological

Diversity

2000

IUCN-Guidelines for the Prevention of Biodersity Loss Caused by

Alien Invasive Species

2000

Guidelines for the Control and Management of ships’ Ballast Water

to Minimize the Transfer of Harmful Aquatic Organisms and

Pathogens

1997

Convention on the Law of Non-navigational Uses of International

Watercourses

1997

Agreement on the Application of Sanitary and Phytosanitary

Meassure

1995

Convention of Biological Diversity 1992

Protocol for the Conservation and Management of Protected Marine

and Coastal Areas of the South East Pacific

1989

ASEAN Agreement on the Conservation of Nature and Natural

Resources

1985

United Nations Convention of the Law of the Sea 1982

Convention on the Conservation of Antarctic Marine Living

Resources

1980

Convention on the Conservation of European Wildlife and Natural

Resources

1979

Convention of Migratory Species of Wild Animals 1979

The Convention on Wetlands of International Importance especially

as Waterfowl Habitat

1971

59

Agreed Measures for the Conservation of Antarctic Fauna and Flora 1964

Plant Protection Agreement for the Asia and Pacific Region 1956

International Plant Protection Convention 1952

-

Chapter 5: Details of some

invasive plants in Bangladesh.

Actually there is no accurate list of invasive plants in Bangladesh. Some researchers

tried to make partial list of invasive plants in Bangladesh, which is described earlier.

Acacia auriculiformis, Eucalyptus camaldulensis, Acacia mangium, Melaleuca

leucodendron, etc. all are blamed of biological invasion in different countries of the world.

In Bangladesh, there are extensive plantation of these trees and also seen as guilty of

having negative impact on indigenous biodiversity. But no doubt that Eupatorium

odoratum, Mikania cordata, Ipomea carnea, Ageratum conyzoides, Imperata cylindrica,

Lantana camara, and water plants like Eichhornea crassipes, Pistia stratiotes etc. are

doing large scale damage to our ecosystem. Description of these plants are given below:

5.1. Akashmoni (Acacia auriculiformis) A Cunn. ex Benth.

Local names: Akashmoni, Akashi, Family: Leguminosae (Mimosoideae)

5.1.1. Akashmoni in Bangladesh : There is no record of how and when A.

auriculaeformis was imported to Bangladesh, but indications are available that the species

60

was first imported by tea planters for its use as a shade tree about 25-30 years ago (Das,

1986). The species is native to the savannas of Papua New Guinea. The Islands of the

Torres Strait and the northern areas of Australia. Because of its ability to grow on very

poor soils or difficult sites, it has been introduced in several tropical countries such as

Solomon Islands, Indonesia, Malaysia, India, Nigeria, Tanzania, The Philippines and

Bangladesh.Now it is an fastly spreading invasive plant in Bangladesh and an important

constituent of plantation forestry throughout Bangladesh.

5.1.2. Description: Acacia auriculiformis is a moderate sized evergreen tree, attaining

a height of 10 m, rarely upto 15m. and 60 cm diameter in about 30 years, which is its

normal length of life. Bark smooth white or light grey, somewhat fissured in later years,

twigs green without spines. The leaf stalks are modified into flattened blade called

phyllode, which is narrowly oblong, slightly curved or sickle-shaped, leathery and dull

green with 4-6 parallel nerves, 8-18 cm long, 1, 2-3, 7 cm broad. Young seedlings have

usually normal leaves. Flowers 4 mm long, tiny, rich yellow, fragrant, crowded in axillary

spikes, 4-9 cm long. Pods are 1.2 cm wide, flat, hard almost woody and much twisted in

irregular coils, initially green but turn brown on ripening. Coiled pod 2.5-3, 8 cm wide,

splitting open along the edges( Luna,. 1996).Fruits are somewhat earshaped, brown,

contorted pods that persist for months.

5.1.3. Distribution: The species is native to the savannas of Papua New Guinea. The

Islands of the Torres Strait and the northern areas of Australia. It ranges from Queensland

(north of about 250S) to the northern parts of the Northern Territory, across southern New

Guinea to the Kei Islands of Indonesia.

5.1.4. Habitat: 4. It grows best under humid, tropical conditions with annual

temperatures of 26oC to over 30oC. However, it is equipped to grow on dry savanna

conditions, since its thick, leathery “leaf” (actually a flattened and expanded leaf stalk,

phyllode) withstands heat and desiccation. A. auriculiformis is drought resistant, that is, it

can survive in areas with a dry season up to 6 months. Although it is well adapted to

drought, it grows most quickly in humid climates. It survives in areas with less than 1,500

mm annual rainfall, however, it is better suited to climates with annual rainfall from 1,500

mm to more than 2,000 mm. In the Northern Territory, Australia A. Auriculiformis grows

mainly on lowland sites, along drainage channels above tidal range, on the edges of dunes,

behind mangrove swamps and along river levees.

61

The tree will grow with practically no maintenance, in a wide range of deep or

shallow soils including sand dunes, mica schist, compacted clay, limestone, podsols,

laterite and lateritic soils. It may also grow in other problem soils such as the eroding

hillslopes, mining spoil, as well as in highly acid and alkaline soils. These problem soils

are often poor in nutrients, however, since A. Auriculiformis produces profuse bundles of

root nodules, it can survive in such areas very low in nitrogen and organic matter where

most eucalyptus and other species fail. In West Bengal, it grows well on red shallow

lateritic soils. Soil pH ranges from 3.0 to 9.0. Its altitudinal range is from sea level to about

600 meters in elevation. Introduced as a fast-growing tree for home and commercial

landscapes. It is frequently used as a street and parking lot tree, institutional plantation,

barren land, and wasteland and degraded site plantation and will survive with little care or

maintenance (Hammer, 2003). Recent works suggest that interactions between plants and soil

microbes are important. Acacia species are able to use soil microorganisms to enhance resource

availability allowing a better resource partitioning than native plants (Ferreira et al., 2003).

5.1.5. Phenology: It flowers profusely at an early age, and continues fruiting almost

continually. In Bangladesh, the seeds are collected from November to April but the best

time is January/February when the pods mature. The production of flower and fruit depend

on the moisture content of the soil. In most cases, flowering occurs twice in a year.

5.1.6. Silvicultural Characteristics: It is a light demanding species. It is moderately

drought resistant, but fails to withstand severe drought, and is fire-tender. It grows very

fast even on marginal land. In Papua New Guinea, A. Auriculiformis planted on too

infertile land grew to 6 m tall in 2 years with a diameter of 5 cm and had reached 17 m in

8 years (Nicholson, 1965).

5.1.7. Natural Regeneration: It is a colonizing species in its native habitat, which

provides the initial ground cover and shading for the establishment of rainforest. It flowers

profusely and produce large amount of seeds, which germinate easily. Big number of

regeneration is found under the tree but because it is an intolerant species, most of the

seedlings are smothered and failed to regenerate in the shade beneath the closed rainforest

canopy. It is only when the canopy is open and large amount of light penetrating to the

ground layer that young regeneration will have the chance to develop.

5.1.8. Ecological threat: Acacia species were introduced as a fast-growing tree,

with the objective to supplement fuelwood and restore degraded lands. However, now

Acacia has become invasive, menacing native flora by reducing native species density and

62

biodiversity. Acacia is exceptionally weedy along roadsides and other disturbed sites and

readily invades habitat and the margins of hardwood forests (Hammer, 2003). The tree is

fast growing and fruits at and early age. Birds are the primary seed dispensers. Once

established in natural areas it can quickly form extensive colonies that replace native

vegetation.

5.2. Mangium (Acacia mangium), Wild.

Local name: Mangium, Family: Leguminosae (Mimosoideae)

5.2.1. Acacia Mangium In Bangladesh: Mangium is a fast growing and fastly

spreading timber species introduced in Bangladesh by the Bangladesh Forest Research

Institute. It has been planted in the forests by the Forest Department (Kabir et al., 1994). It

was first introduced in this country in 1979 and later in 1980. The species has been

introduced to Bangladesh and is being planted since 1983 (Latif et al., 1993).

5.2.2. General Description: Acacia mangium grows as tall as 30 m with a straight,

clear bole that may be unbranched for more than half its total height. Stem dimeters up to

90 cm have been recorded in the natural forests of Queens land and Papua New Guinea.

The bark of older trees is thick, rough, and hard, and is furrowed longitudiually and varies

from dark brown to fawn in color. The inflorescence is a loose spike up to 10 cm long,

made of small white or cream flowers (Latif et al. 1984).

5.2.3. Distribution: It is native to three small areas of Queensland, Australia, the

South Western portion of New Guinea and the Molluca Island, of Eastern Indonesia.

Populations extend from a northern limit in Irian Jaya of 0o50’S to the most southern

occurrence in Queensland, Australia at about 19oS. It was introduced in Sabah in 1966 and

in 1978 in Bangladesh.

5.2.4. Climatic Conditions: Experiment conducted in Bangladesh since 1979 had

indicated that the species can be grown even in dry and poor soils, especially in the hilly,

barren and undulating areas. It also competes well with Imperata grass (Das, 1984). On

good sites in Bangladesh, the tree had an average height of 8 m and an average diameter of

7.7 cm. In its natural habitat (Queensland, Australia) it is a pioneer species which

establishes itself often sites have been disturbed. It occurs principally in the coastal

63

tropical lowlands, on the fringes of mangrove as well as in reverine forests. It does not

occur in mature rainforest but is most often found on the forest margins.

5.2.5. Ecological threat: A. Mangium is a very profilic seeder. Abundant

regenerations are reproduced in the natural stand. As a pioneer species, the trees occur in

small groups, then may occasionally dominate large areas. It establishes itself after sites

have been disturbed, particularly by fire. The seeds can remain viable for more than one

year, and fire naturally scarifies them and enhance germination. The stumps of young trees

coppice.

5.3. Eucalyptus Species

5.3.1. Eucalyptus Introduction in Bangladesh: Eucalypt has a long history in

Indian subcontinent. It was first planted around 1790 by Tippu Sultan, the ruler of Mysore,

in his palace garden on Nandi hills near Bangalore. According to one version he received

seed from Australia and introduced about 16 species (Shyam S. 1984). But according to

Tanvir (1996) its first introduction in the sub-continent dates back to 1843 as single trees,

arboreta and roadside plants. Eucalypt has come to stay in India (Palanna, 1996).

Sometime in the 1930’s Eucalyptus citriodora was haphazardly introduced into eastern

Bangladesh by tea estates as an ornamental. This species was spread throughout

Bangladesh by botanists, foresters, gardeners and other people, but no formal plantations

were developed (Davidson and Das, 1985). First interest in other species of eucalypts was

recorded in 1963 when germination tests of three species, E. citriodora, E. tereticornis and

E. botryoides were conducted in the Silvicultural Research Ranges in Mymensingh and

Chittagong. From then on until 1984 about 37 species were introduced and tried

excluding those introduced in the tea estates. After five years of experimentation, the

Bangladesh Forest Research Institute in Chittagong have arrived at a conclusion that E.

camaldulensis, E. tereticornis and E. brassiana could be profitably grown in the soil and

climatic conditions of Bangladesh (Das 1984; Davidson, 1985). Out of the little more than

one million ha of land under existing forest in Bangladesh (FAO 1995), eucalyptus

occupies a substantial land area. Besides, eucalyptus enjoys a good popularity in social

forestry, home garden and even in the cropland agro-forestry practice in our country. (Paul

et al., 1998). Eucalyptus camaldulensis of Petford provenance is being planted fairly

widely on a commercial basis for fuelwood and other purposes in Bangladesh.

64

Eucalypts are amongst the most widely planted trees in the world. Because of their

fast growing character and outstanding physiological, genetic and silvicultural attributes

(Davidson 1985), these trees are extensively used for afforestation and reforestation in 58

countries (FAO 1981)

5.3.2. Eucalyptus camaldulensis, Dehnh

Local name: Eucalyptus, Family: Myrtaceae

5.3.2.1. General Description: It is a large-boled tree in its natural habitat, medium-

sized to tall tree, reaching up to 25 meters tall, with erect or spreading branches and a

smooth bark that may be pink, cream or white. Occasionally, the dbh is 1-2 meters. The

trees are often crooked. Juvenile leaves, ovate to broadly lanceolate, tend to be pendant;

adult leaves, narrow lanceolate, alternate, petrolate.

5.3.2.2. Distribution: This is the most widely distributed of all eucalyptus, occurring

along or near almost all of the seasonal water courses in the arid and semi-arid areas. It is

widely planted in plantations throughout the world ranging from the Mediterranean, Spain,

Morocco, Pakistan, Uruguay, Argentina, Kenya, Nigeria, Tanzania, India, Bangladesh, etc.

In its natural state, the latitudinal range is about 12.5o - 38oS. It is one of the most widely

spread eucalyptus in Australia occurring naturally in all the Australian states except

Tasmania.

5.3.2.3. Climatic Condition: This species grows under a wide range of climatic

conditions from warm to hot, sub-humid to semi-arid with the mean maximum

temperature for the hottest month in the range 27o – 40o C and the mean minimum for the

coldest month around 3o – 15o C. In the native habitat the mean annual rainfall range is

mostly 250 – 600 mm, while a few areas receive up to 1250 mm and same as little as 150

mm.

5.3.2.4. Physiographic, Edaphic and Biotic Requirements: The species is usually

found on acidic soils (pH 4.5-5.5) of low fertility, low in phosphorus, shallow and sandy

and even in some sites it tolerates passing floods (Salazar 1988).

It is also adapted to sandy alluvial soils. It perform very poorly on calcareous and

shallow soils over limestone. It is important to know the right provenance for planting in a

given site condition as the seed from a specific origin may grow better in a specific site.

65

Although the tree is a riverine species of the plains it can be grown in highland areas of

over 1200 meters. However, for better growth development it should not be planted on

areas higher than 700 meters.

5.3.2.5. Forest Types: It occurs along or near almost all of the seasonal watercourses

in the arid and semi-arid areas and is found along many other stream and rivers in the

southeast of Australia.

5.3.2.6. Silvicultural Characteristics: A light demander species in favourable sites,

Eucalyptus camaldulensis grows very fast. With the right provenance planted in

plantation, mean annual growth increments of 2 meters in height and 2 cm in diameter can

be maintained for the first 10 years. One good sites, plantations are managed on coppice

rotations of 7-10 years(Davidson and Das 1985). The species has a high root-shoot ratio,

which accounts for its drought resistance. Natural regeneration is reported under the

mother trees of 105 cm dbh for the first time from Sriganganagar (Rajashtan) on alluvial

sandy soil having good moisture due to irrigation (Nautiyal et al., 1994)

5.3.2.A. Criticism on Eucalypts:

At present eucalypt planting around the world extends to about 80 countries and

another 50 countries are in trial phases. Eucalypt planting is a controversial issue in some

countries where it has been planted extensively. Critics assert that: i) it has deleterious

effect on the hydrological balance; ii) it depletes the soil nurtrints; iii) it has an allelopathic

effect leading to inhibition of growth of other plants; and iv) it has a deleterious effect on

native animals (Ali, 1996).

5.3.2.B. Attributes of introduced Eucalypts:

It is important to understand the attributes of eucalypts planted in Bangladesh to

understand their environmental consequences. The most outstanding eucalypts introduced

are E. tereticornis and E. camaldulensis. These species, including others introduced

elsewhere as exotics, as E. grandis and E. urophylla in the Indo-Malaya region, tend to

have a number of characteristics in common:

a) They belong predominantly to the subgenus Sumphyomyrtus – individual members

of which may be characterized by a wider environmental tolerance than members of other

subgenera.

66

b) They are the more successful species capable of responding more positively to

better soil conditions- particularly higher soil fertility.

c) They are capable of rapid root development, particularly in depth. This may be a

general attribute of eucalypts growing, or capable of growing, away from moist regions.

d) The species usually reach early and strong peaks in current annual volume

increment (CAL). This peak may be as early as 4 years in E. tereticornis, 6-7 years in E.

grandis and 12-15 years in E. globulus. By the time the peak is reached wood volume

production on high quality sites may be in the range of 24 m3/ha/yr for E. tereticornis to

50 m3/ha/yr for E. globulus (Florence, 1992).

5.3.2.B.1. Water use by eucalypts:

Claims are made that eucalypts use excessive amounts of ground water by developing

a deep root system. In dry areas, though eucalypts develop long deep tap root in moist

areas, they mostly develop fibrous roots (Zimmer and Grose, 1958). Dabral et al. (1987)

observed that the fibrous root of eucalypts extend up to 18 m within a soil depth of 30 to

60 cm in moist areas. When moisture content varies at different localities of a site,

eucalypts may try to maintain growth by extending root systems in drier areas.

Where a eucalypt is planted in countries other than Australia, it is removed from its

regulated environment context, and the checks and balance imposed by site no longer

apply. For example, E. camaldulensis occurs naturally as a woodland in dry areas over

most of the Australian continent where the rate of water use is hardly an issue in the

Australian circumstances (Florence, 1992), it could become and issue where it is

established elsewhere as a forest on moderately fertile soil with good rooting depth and

access to a water table.

It is possible that where one of the more opportunistic of the faster growing

eucalyptus (e.g. E. camaldulensis) has access to a substantial water resource and where

there is a prolonged dry period with high vapour pressure deficts, large amounts of water

may be transpired (Florence, 1992).

5.3.2.B.2. Effect on soil fertility:

67

Eucalypts absorb a large amount of nutrients to maintain fast growth. Recent opinions

conclude that eucalypts could lead to the decline of soil fertility, as the forest land quality

in eucalypt plantation declines.

George (1986) concluded that the organic matter and exchangeable potassium are

depleted in the soil under eucalypt plantation than in woodlands, but no difference in

calcium and magnesium was observed.

In a study carried out in the Dry zone in Srilanka, it was observed that the soil under

Eucalyptus camaldulensis tend to become slightly acidic with the increase in depth

(Ranasinghe and Jaysuriya, 1991).

Scientific evidence from Sri Lanka made in short and long rotation eucalypt

plantations confirm findings reported from many other countries (Poore and Fries, 1985)

and Shiva and Bandyopadiyay (1985).

Impervious and/or highly erodible soils will be washed away more easily than porous

soils. One of the factors which can make soils under eucalyptus impervious is a non-

wettable or water repellent property which is found in both natural stands in Australia

(Hamilton 1964, Davidson 1967) and under exotic plantations water repellent soils are

abnormal soils which resist wetting by water , a behaviour which is caused by a

hydrophobic coating of organic origin on the soil particles (De Bano 1971). Water

repellent soils cause impeded infiltration and percolation, resulting in water moving over

and through the soil (Davidson 1967), causing patchy wetting of the upper soil horizons.

Blocks of soil near the surface may remain dry after considerable rainfall (Davidson

1967).

Water repellency is of course not restricted only to soils under eucalypts. It is also

commonly associated with certain other species and vegetation types such as citrus

orchards (Jamison 1942).

Other conditions being similar, the precipitation reaching the ground is 20-25 percent

more in eucalypts plantation than in the plantations of other broad leaved species (Hassan

1994).

Eucalypts leaf contains growth inhibitor such as tarpenes. This compound prevents

the germination of herbs and shrubs intended for underplanting. This has been proved to

be strong when the leaves are fresh, but the effect becomes faded as the leaves decay and

the inhibitor compound volatilizes (Hassan, 1994).

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5.3.2.B.3. Alletopathy /understory vegetation and eucalypts:

It is widely held in some countries, notably India, that eucalypts are strongly

allelopathic; that they produce foliar and root exudates directly toxic to other plants. It is

more likely that the effect of eucalypt on understory plants or adjacent crops are the result

of the very great capacity of eucalypts to complete for short supply soil resources

(nutrients and water). Where soil resources are not in short supply the understory

vegetation may be maintained under a vigorous tree canopy.

In India Dabral et al. (1987) found an undergrowth vegetation of Lantana spp.,

Murraya koenigii, Carissa karonda, Jasminum officinale, Mallotus philippensis and

Syzygium cumini under 16 year old eucalyptus hybrid plantation, at spacing 2m x 2m, at an

experimental site near Dehra Dun Forest Research Station. In our forest conditions

undergrowth under eucalypt plantings at 1.8m x 1.8m spacing but the diversity is less than

of native forest types. The composition observed could have been disturbed by weeding,

ground fire and shrub collection of local people and a confirmation study of the diversity

of undergrowth needs to be made under suitably undisturbed eucalypt plantation.

Lisa and Michelsen (1993) reported in Ethiopia that eucalypt leaf exudates have some

inhibitory effect on germination, and on reduction of shoot dry weight of four crops tested;

they state an allelopahaic potential rating from lower to higher as Cupressus lusitanica <

E. globulus < E. saligna < E. camaldulensis.

The nutrient accumulation is generally greater in species with a comparatively larger

crown biomass relative to stem size. The rangs of nutrient accumulation in E.

camaldulensis was established by Hopmans et al (1990). A considerable amount of N

accumulated in the leaves and twigs of eucalypt can be left in the forest environment, and

would compensate for the loss to some extent but in case of other macro nutrients some

corrective measures may have to be taken. This is very important, especially in the case of

eucalypts, because nutrient content in the litter of eucalypt is lower than other species as

they usually absorb nutrients before the shedding of litter (Banks, 1992).

5.4. Ipil-ipil (Leucaena leucocephala) (Lamb) de wit Family: Leguminosae (Mimosoideae) Local name: Telekadam; Common names: Ipil-ipil, house tamarind, white babool.

69

5.4.1. General Description: Depending on variety, leucaena is either a tall, slender

tree that may grow up to 20 m, or a rounded, many-branched shrub less than 5 m high.

Generally, the leaves are evergreen, alternate, bipinnate with 3-6 pairs of pinnae, each of

these with 10-20 pairs of sessile, narrowly oblong to lanceolate feathery leaves, often

almost translucent. The flowers are small, white and fluffy balls, usually self-ppllinated

and produce thin flat almost straight pods. More than 800 varieties of this species are

known

5.4.2. Distribution: The species is probably native to Mexico and northern central

America, and introduced to Indonesia, Philippines, Malaysia and other countries in South

East Asia, Hawaii, Northern Australia, India, Bangladesh, East and West Africa and

islands in the Pacific and Caribbea.

5.4.3. Habitat: Leucaena grows under a wide variety of climatic conditions, though it

is a tree of the tropics and sub-tropics where it grows upto an elevation of 500 m. The

species is capable of tolerating large variations in rainfall, temperature, wind, drought and

topography (NAS, 1977). The root system is characterized by well developed and deep

taproot which is capable of even breaking the impervious layer (Gray, 1968).

5.4.4. Silviculture Characteristics: This species is very light demanding. It grows

best in full sunlight and in high light intensities. Leucaena coppices readily from stumps of

almost any age. Coppice growth is more vigorous than seedling growth, new shoots of

Giant varieties reach 6 m in one year.

The species is an aggressive colonizer. Because of its copious seed producing nature

and special seed dispersal mechanism of ripe seeds splitting naturally along both the edges

of the pod and ejecting 15-30 seeds per pod it easily escapes from cultivation and colonise

the adjoining agricultural fields. The pods fallen on the ground are also dispersed by

animals, wind etc(Patil & Kumar, 1990). Ipil-Ipil can naturally regenerate by seed and

coppice (Zabala, 1985). Since the species is prolific seeder, harvesting the crop by clear

cutting exposes the seeds to sunlight (being scarified), then profuse growth of seedlings

follow.

5.4.5. Ecological threat: Invasion by Leucaena leucocephala and its impact on the

native plant community: Leucaena leucocephala is native to Central American savannas.

It is an invasive leguminous shrub that has become naturalized on many countries. It forms

dense thickets in disturbed areas. The invasion of L. Leococephala promotes the invasion

70

and establishment of more aggressive alien tree species. Consequently, the invasion and

expansion of L. leucocephala has had a severe effect on the native plant community

(Yoshida and Shuichi, 2003). Leucaena is a weedy, fast-growing tree that readily invades

coastal strand, pine rockland, the margins and canopy gaps of hardwood forests, and open

disturbed sites. Population densities can be high if left unchecked. (Hammer, 2003).

5.5. Melaleuca (Punk Tree).

Melaleuca quinquenervia S. T. Blake

Melaleuca leucodendron L. f.

Family:Myrtaceae.

5.5.1. Melaleuca debate: In the 1970’s, the popularity of melaleuca took a hit.

Biologists and land managers are now beginning to curse melaleuca as it spread

unchecked across the landscape at the expense of native plants. Severe wildfires were

being blamed on the prevalence of melaleuca. Melaleuca is now a scapegoat for people’s

itchy eyes and runny noses. Biologists and land managers were now thinking of ways to

rid themselves of the melaleuca menace (Pernas and Francois, 2003). Melaleuca rapidly

invades moist, open habitats, both disturbed and undisturbed, and forms dense,

impenetrable forests. In general, invasion is less prominent on forested sites than marshes.

5.5.2. Native range: Eastern Australia through Malaysia and Myanmar (Burma).

5.5.3. Description: Melaleuca is a large evergreen tree typically 65-100 feet in

height with brownish white, many-layered papery bark. Melaleuca (Melaleuca

quinquenervia) trees grow quickly, typically 3-6 feet per year in marshes and swamps.

An upright, slender tree usually single-trunked but may develop multiple trunks. Trunk

and branches covered with thick layers of white, papery bark, peeling off in sheets. Leaves

are dull green, 2 to 8 inches long and 3/8 to ½ inch wide, stiff and highly aromatic when

crushed. Flowers are showy and produced in bottlebrush-like spikes with prominent ivory-

white stamens. Fruit broadly cylindrical, thick-walled, capsules to 3 mm (3/8 in) wide,

in clusters surrounding young stems; each capsule holding 200-300 tiny seeds. Dust-like

seeds are enclosed in rounded, tightly clustered, persistent, greyish-brown capsules

produced along the stems.

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5.5.4. Ecological threat: Melaleuca causes both ecological and public health

problems. It rapidly colonizes freshwater wetlands, almost completely displacing native

vegetation and degrading wildlife habitat. Any physical disturbance, such as fire, freezes,

felling, and even herbicide application liberates millions of seeds from a single tree. The

tree can reproduce from seed when only one or two years old and is still undergoing rapid

population expansion in the Big Cypress National Preserve and the northern portion of

Everglades National Park. Melaleuca also constitutes a significant health hazard because

the flowers and new foliage produce airborne substances that cause severe asthma-like

symptoms in sensitive people.

Invasive characteristics of Melaleuca include its evergreen habit, prolific seed

production, frequent flowering and flood and drought tolerance. This tree threatens

biodiversity of native flora and fauna by diminishing the value of their habitat (Serbesoff-

King, 2003).

This non-native tree is a notorious invading tree in different countries of the world, as

for example, rapidly displacing native cypress and sawgrass in the Everglades(U.S.A.).

Melaleuca can flower five times per year. Any damage to the tree that cuts water flow to

the stems containing seed capsules, such as fires, freezes, and control techniques, will

result in seed release. Seeds can remain viable for 10 years, and a single tree can store

2-20 million seeds.

5.5.4.1. Environmental damage caused by melaleuca

Melaleuca forms dense stands resulting in the almost total displacement of native

plants that are important to wildlife.

Melaleuca forests represent a serious fire hazard to surrounding developed areas

because of the oils contained within the leaves that create hot crown fires.

Melaleuca forests provide relatively poor habit for wildlife and almost totally

displace native plant species

Melaleuca invasions alter the landscape of the Everglades by creating

monospecific forests in formerly treeless sawgrass marshes.

Melaleuca forests alter ecosystem properties such as water flow in the Everglades.

Dense stands of melaleuca trees produce hot crown fires that result in native tree

mortality and pose a significant threat to developed areas.

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5.6. Dul kolmi ( Ipomoea carnea) .

Invasion by Ipomoea carnea: Invasiveness of certain introductions has been obvious

because of their rapid expansion and widespread detrimental ecological impacts. Ipomoea

carnea, a native of South America has spread fast in Indian subcontinent during the last

three decades and has become an obnoxious aquatic weed (Kandasamy, 2003).It is a

Common weed of all habitat In Bangladesh(Hossain and Pasha, 2001). It is a perennial

diffuse or straggling shrub growing to a height of 2-3 m. Can come up in waterlogged

areas and is resistant to drought. Widely seen in roadside and farm ditches, waterlogged

areas, shorelines, river-sides. In Bangladesh it is seen in almost all districts

5.7. Ageratum conyzoides

Family: Asteraceae

Invasion by Ageratum conyzoides – the exotics from South America (with wide

ecological amplitude apart from effective and well-organized dispersal mechanism) have

overpowered natives and caused much ecological harm because of their invasion, density

of native flora and crop productivity has diluted affecting adversely the socio-economic

condition. How their strong allelopathic potential and colonizing character has changed

the soil fertility, the ecological succession and thereby whole ecological dynamics (Kohli

and Kuldip, 2003).

It is a Common weed of waste and cultivated field in Bangladesh; blamed as

aeroallergic pollen species (Hossain and Pasha, 2001)

5.8. Siam weed (Chromolaena odorata (L.)

Family: Asteraceae

5.8.1. Intriduction: Of all the species under the genus Chromolaena, Siam weed

(syn. Eupatorium odoratam.) is the best known because of its wide distribution.

Chromolaena odorata (L.) is a dominant, competitive and difficult invasive species in the

humid forest zone of Western and Central Africa (Ngobo et al., 2003) Other affected

countries are West Africa, South Africa, the Indian subcontinent, and the Pacific. In

73

Bangladesh it is a common invasive weed of fallows and bush fallow sites, wasteland and

forests.

5.8.2. Origin: Originating from South and Central America it later reached Southeast

Asia in the 19th century. Singapore was the first entry point and became present in other

Asian countries.

5.8.3. Vegetative characters: C. odorata is a perennial shrub, which attains a height

of 3 m and grows well in open areas, riverbanks, creeks and plantations of coconut, palm

oil, citrus, tubers and rice. In shaded areas, it could reach a height of 10-20 m, adopting a

climbing habit. It grows at a rate of 20mm/day or 5 m/year.

Chromolaena odorata was appreciated for its ornamental value, having pale purple

and offwhite-coloured small flowers blooming during winter. This probably led to its other

name “Christmas bush”. Because the flowers are produced in masses, they tend to cover

the whole plant. It continues to flower for three to five dry and windy months. Seed

production is prolific with up to 87,000 seeds per mature plant or 400,000 per square

meter having been recorded. Seeds germinate readily (Khanna, 2003). The condition

favours rapid drying of fruits and dissemination to wider ranges as well. Seeds are also

dispersed by sticking to clothings, farm implements, vehicles, footwear and animals. Seeds

may soon germinate after rain or remain viable in the soil for five or longer years. It is also

valued as a good ground cover

5.8.4. Chemical Compounds: Alkaloids, camphor, vitamin C, eupatorin, tannin,

essential oil, sesquiterpene.

5.8.5. Negative impact of chromolaena: Consumption of leaves and young shoots of

C. odorata by pasture animals may endanger their lives. It may cause diarrhea, abortion

and worse, death due to its high nitrate content. As a result, unmanaged areas are always

left as wastelands. In a one-hectare land, biomass production of C. odorata averages 15

tons. For humans, it may cause allergies, asthma and skin problems. Dried patches of the

weeds burn easily, opening new areas ready for invasion.

Chromolaena-dominated fallows and bush fallow site increasing intensity of land

management seemed to be a significant predictor of falling plant diversity (Ngobo et al.,

2003). Increased level of land use intensity associated with increased level of disturbances

in fallows correlate with the Chromolaena. dominated fallow type, and seem to facilitate

the invasion by weeds, both during the fallow phase and the subsequent cropping season..

74

Chromolaena was ranked as the farmers’ most important constraint to crop production in

short duration fallow systems. The species is not only consistently abundant throughout

the cropping period, but it was also dominant in fields established after clearing less

intensively farmed fallow types This species has been nominated as among 100 of the

“World’s Worst: invaders (Ngobo et al., 2003).

5.8.6. Control: Chemicals may be applied to immediately suppress the weed but

these are expensive and dangerous to some extent. Slashing of the weed is also an

ineffective control because new shoots may develop from broken and cut stems.

Biological control is still recommended such as the use of Pareuchaetes pseudoinsulata, an

archtiid moth belonging to Lepidoptera. It may be successfully established in countries

such as Malaysia but not in other areas. The agent is a voracious leaf-feeder. Other

biological agents are still being considered like Procecidochares connexa, Mescinia

parvula, Melanagromyza eupatoriella (David, 2002).

5.9. Son/Cogon Grass (Imperata cylindrica)

Family: Poaceae

5.9.1. Invasion by cogongrass (Imperata cylindrica): A Native to Southeast Asia is a

listed invasive weed in many countries. Cogongrass (Imperata cylindrica) also called Son

is an aggressive, colony forming dense erect perennial grass 1 to 5 feet (30 to 150 cm) in

height. Older infestations will be more difficult to control (Miller, 2003). A Federal listed

noxious weed (Miller, 2003). Cogongrass [Imperata cylindrical (L.) Beauv.] a

rhizomatous perennial grass, is a serious pest in many areas and situations, covering over

500 million acres throughout the world. However, it may be possible to suppress

cogongrass regrowth by introducing native vegetation after initial chemical control

measures have been employed. Also, an understanding of herbicide residues in various

soil types is crucial in the selection of desired native plant species to be incorporated into

this suppression scheme (Macdonald et al., 2003; Mack, 2003).

5.9.2. Description: Cogon grass is an erect, perennial grass. Aggressive,

colony-forming dense perennial grass 1 to 5 feet (30 to 150 cm) in height, often leaning in

mats when over 3 feet (90 cm) in height. Stem Upright to ascending, stout, not -apparent,

and hidden by overlapping leaf sheaths. Stem less tufts of long leaves, blades yellow

green, with off-center midveins and silver-plumed flowers and seeds. Flowers in February

to May Terminal, silky spikelike panicle, 1 to 8 inches (2.5 to 20 cm) long and 0.2 to 1

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inch (0.5 to 2.5 cm) wide, cylindrical and tightly.branched. Spikelets paired, each 0.1 to

0.2 inch (3 to 6 mm) long, obscured by silky to silvery-white hairs to 0.07 inch (1.8 mm).

Seeds in May to June. Oblong brown grain, 0.04 to 0.05 inch (1 to 1.3 mm) long, released

within silvery hairy husks for wind dispersal Culms area mostly erect and unbranched,

with reduced blades and open sheaths (Holm et al., 1977; Bryson and Carter, d1993).

Cogon grass is strongly rhizomatous with extensive, sharply pointed, creeping scaly

rhizomes (Holm et al., 1977).

5.9.3. Taxonomy: The genus Imperata, family Poaceae, subfamily Panicoideae,

supertribeAndropogonodae, tribe Andropogoneae (Gabel, 1982; Watson and Dallwitz,

1992),subtribe Saccharinae, includes nine species worldwide. Hubbard et al. (1944)

recognized five varieties of I. cylindrica worldwide.

5.9.4. Geographical Distribution: Cogon grass has been reported as a weed in 73

countries and on all six countries. It is widely distributed in Africa, Australia, southern

Asia, and the Pacific Islands, and less extensively distributed, or a less serious problem, in

southern Europe, the Mediterranean, the Middle East, Argentina, China, Colombia, the

Caribbean, and the southeastern United States. It has been found at latitiudes from 450N (Japan) to

450S (New Zealand), and from sea level to over 2,000 m elevation (Holm et al., 1977).

5.9.5. Ecology: Grows in full sunlight to partial shade, and, thus, can invade a range

of sites. Often in circular infestations with rapidly growing and branching rhizomes

forming a dense mat to exclude most other vegetation. Aggressively invades

right-of-ways, new forest plantations, open forests, old fields, and pastures. Absent in

areas with frequent tillage. Colonizes by rhizomes and spreads by wind-dispersed seeds

and promoted by burning. Highly flammable and a severe fire hazard, burning extremely

hot especially in winter (Miller, 2003).

5.9.6. Pest status: Cogon grass, Imperate cylindrica (L.) Beauv., has been ranked as

one of the ten worst weeds of the world (Holm et al., 1977). In tropical and subtropical

regions around the globe, this aggressive, rhizomatous perennial is generally considered a

pernicious pest plant due to its ability to successfully disperse, colonize, spread, and

subsequently compete with and displace desirable vegetation and disrupt ecosystems over

a wide range of environmental conditions (Holm et al., 1977; Brook, 1989; Bryson and

Carter, 1993; Dozier et al., 1998).

Son has been reported as a problem in more than 35 annual and perennial crops,

including rubber, coconut, oil palm, coffee, date, tea, citrus, forests, field crops (rice), and

76

row crops (corn) (Holm et al., 1977; Brook, 1989). Problems with Cogon grass often have

arisen on lands cleared of natural forest, which are then quickly colonized by Cogon grass

before cultivation, during plantation establishment and growth, or soon after the

abandonment of land used for short-duration shifting agriculture (Brook, 1989). Left

unchecked, colonized area become densely infested with Cogon grass, are difficult to

convert to other vegetation. Cogon grass infestations damage crops through competition,

causing suppressed growth, reduced yields, and delayed harvests.

5.9.7. Ecological damage: Cogon grass’ tendency to form dense, persistence and

expanding stands allows it to displace other vegetation. Its abundant biomass prevents

recruitment of other plants and changes the properties of the litter and upper soil layers

(Lippincott, 1997). Extensive rhizome reserves of Cogon grass enable it to quickly regrow.

Also, fires induce flowering and seeding, reduce competition from other plants, and

creating opening for seedling establishment (Bryson and Carter, 1993; Dozier et al., 1998).

More than 500 million ha of Cogon grass have been estimated to occur worldwide

(Holm et al., 1977). In Asia, where an estimated 200 million ha are dominated by Cogon

grass, infested areas are increasing at a rate of 150,000 ha annually (Soerjani, 1970).

Cogon grass has invaded a variety of habitats, from highly xeric uplands to fully shaded

mesic sites. Sandhills, flatwoods, hardwwood hammocks, sand dunes, grasslands, river

margins, swamps, scrub and all are invaded by Cogon grass. In addition, Cogon grass can

significantly alter the structure and function of invaded communities (Holm e al., 1977).

5.10. Lantana (Lantana camara)

Family: Verbenaceae

5.10.1. Introduction: Lantana is a land plant, widely grown as an ornamental shrub

throughout the tropics, subtropics and temperate zones, it is established as a weed of

pastures and the environment in ca. 50 countries.

5.10.2. Description: Much branched, thicket forming shrub normally 2-4 m but

capable of becoming a liana up to 15 m tall. Rambling, pubescent perennial shrub,

branched 4 – angled, prickly. Leaves opposite, ternate, strongly smelled. Flowers in

peduncles, cylindrical spikes. Sepal 4-5 toothed calyx, petals 4-5, connate in a cylindric

corolla with slender tube, orange-yellow. Stamens 4. Fruit is a fleshy dry drupe. Flowers

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all year round, main season autumn to winter. Flowers from white to red with variations in

between, including purple.

5.10.3. Habitat: Along roadside, village thicket, jungles, tea plantation, mixed forest.

Found all over the country.

5.10.4. Reproductive Mode: Year round flowering. Self and cross-pollination. Large

fruit and seed set. Fruit a small drupe with 1 seed. Lantana does not sucker from damaged

or broken roots but will regrow from the base of the stem and from rooted horizontal

stems in contact with moist soil.Concentrates nitrogen in the soil. Produces allopathic

compounds.

5.10.5. Reproductive Output: 24 fruits per inflorescence, 511 inflorescences per

plant, 12,265 fruits per plant (Khanna, 2003).

5.10.6. Medicinal Value: Its leaves have insecticidal properties, used in many skin

diseases. Barks used in rheumatic complications.

5.10.7. Chemical Compounds: Camphor, Sterol, tannin.

5.10.8. General Impacts: Decreased productivity in pastures. Poisons cattle. Invades

disturbed natural ecosystems establishing in open situation creek banks and roadsides.

Excludes understorey species. Changes faunal makeup by providing perch sites and cover.

Understorey competitor for forestry.

5.10.9. Lantana a poisonous plant: Lantana plant poisoning is seen in all grazing

animals, like cattle, sheep, and goats. Lantana plant contains certain hepatic toxins, namely

Lantadene A and B. The former is more toxic that the latter. They can cause liver damage

or degeration resulting in its dysfunction and digestive disturbances. Bile ducts in the

river are also damaged and fibrosed become hard. This can lead to bile retention in the

liver and jaundice or yellowish discoloration of skin and mucous membranes. Jaundice

also induce severe digestive troubles and weakness. Moreover, a photodynamic substance,

namely phyloerythrin is produced from the chlorophyll of lantana plant leaves. This

substance appear in the skin as a photosensetiser. When sun light falls on the skin, it reacts

mostly at the unpigmented parts like muzzle, face, ears leading to local inflammatory

reaction or dermatitis. These changes are followed by secondary bacterial infections and

diseases. Death is due to liver damage and severe weakness clubbed with jaundice, skin

damage and concomitant diseases.

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Lantana poisoning is of two types, on is acute and the other chronic. Acute form is

seen when animals consume large amounts of it and chronic when they take small

amounts for longer periods. In acute form, animals suddenly become dull and depressed.

They refuse food. There is dysentery followed by marked dullness and paralysis of legs.

Death may supervene, when they are not treated specifically for it. In chronic form,

animals become slowly dull and morosed. There are excessive salivation and yellowish

discoloration of skin and mucous membranes(Christopher, 2001).

5.10.10. Control: Control must be integrated, including manual removal, burning,

shading, chemical control and revegetation. In many cases natural restoration is difficult

after removal of thickets, due to reduced seed banks of native species. Long history of

international biological control, however few are effective to date (Khanna, 2003).

5.11. Assamlata (Mikania cordata) Family: Compositae

5.11.1. Description: Twining, strongly branched climber with limited life-span, 5-

10m long, stem slender, younger parts finely pubescent. Leaves opposite, ovate to ovate

triangular with deeply cordate base, acuminate apex, slightly dentate. Flowers 4.5-6 mm

long, numerous, peduncled, in axillary or terminal, dense coryms. Corolla white,

campanulate. Fruits, achenes blackish brown. Flowers mostly during dry season.

5.11.2. Habitat: Forest, wasteland, agricultural land, roadside, plantation, jungle.

Found in the Sylhet and Chittagong Hill Tract regions. The climber also grows in many

other countries.

5.11.3. Medicinal Value: Rich source of vitamins A, B and C. Leaves used against

snake bites. It has also bitter substances and tannin.

5.11.4. Ecological threat: Mikania cordata has become a serious problem in

Bangladesh, India, Srilanka, Thailand, Phillippines, Mauritius, Malayasia, Indonesia, and

many of the pacific islands. Once established, the plant becomes rampant and covers other

plants. It then suppresses other plants by cutting out the light and smothering them.

Though many plants are damaged by Mikania cordata some plants can grow with it. These

include Ageratum conyzoides Lantana camara etc. Mikania cordata ‘s harm is

unquestionable and it is an urgent but difficult task to control the plant.

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Aquatic invasive plants: Literature on two aquatic plants of Bangladesh, Water

Hyacinth (Eichhornia crassipes) and Waterlettuce (Pistia stratiotes) has been given

below:

5.12. Water Hyacinth (Eichhornia crassipes)

Family Pontederiaceae

5.12.1. Introduction: Waterhyacinth is one of the world’s worst aquatic invasive

weeds. It is one of the worlds 100 most invasive plants.

5.12.2. Description: Waterhyacinth is an erect, free-floating, stoloniferous, perennial

herb. The bouyant leaves vary in size and morphology. The short, bulbous leaf petioles

produced in uncrowded conditions provide a stable platform for vertical growth. Plants in

crowded conditions from elongate (up to 1.5 m) petioles (Center and Spencer, 1981).

Leaves are arranged in whorls of six to 10, and individual plants develop into clones of

attached rosettes (Center and Spencer, 1981). Seed capsules normally contain fewer than

50 seeds each (Barret, 1980). Each inflorescence can produce more than 3,000 seeds and a

single rosette can produce several inflorescences each year (Barrett, 1980). The submerged

roots (rhizoids) are relatively long and "feathery", extending as much as 1 m below the water.

The small long-lived seeds sink and remain viable in sediments for 15 to 20 years

(Matthews, 1967; Gopal, 1987). Seeds germinate on moist sediments or in warm shallow

water (Haigh, 1936; Hitchcock e al., 1950) and flowering can occur 10 to 15 weeks

thereafter (Barrett, 1980). Populations increase mainly by vegetative means.

5.12.3. Taxonomy: Waterhyacinth is the standardized spelling adopted by the Weed

Science Society of America (WSSA, 1984) to denote that it is not an aquatic relative of

true “hyacinth” (Hyacinthus spp.), as the two-word spelling suggests. The taxonomic

placement of Waterhyacinth, based on Cronquist (1988), Thorne (1992), and Takhtajan

(1997), is as follows: division Commelinidae (Liliidae [Cronquist, 1988; Thorne, 1992];

superorder Commelinance (Thorne, 1992), order Pontederiales (Liliales [Cronquist, 1988];

philydrales [Thorne, 1992]); family Pontederiaceae, genus Eichhormia; specific epithet

crassipes (Martius) Solms-Laubach.

5.12.4. Distribution: This South American native is one of the worst aquatic weeds in

the world it is now found in more than 50 countries on five continents (IUCN, 2003)

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5.12.5. Pest status of weed: Waterhyacinth, Eichhormia crassipes (Mart.) Solms.-

Laubach, is considered one of the world’s worst weeds (Holm et al., 1977), invading lakes,

ponds, canals, and rivers. It was introduced into many countries during the late 19th and

early 20th centuries, where it spread and degraded aquatic ecosystems. It is still rapidly

spreading, where new infestations are creating life-threatening situations as well as

environmental and cultural upheaval (Cock et al., 2000).

5.12.6. Economic Damage: The costs of water hyacinth invasion are often in millions

of dollars and its control is expensive and time-consuming. Waterhyacinth grows rapidly

(Penfound and Earle, 1948) forming expansive colonies of tall, interwoven floating plants.

Water hyacinth is a very fast growing plant, with populations known to double in as little

as 12 days (IUCN, 2003). E. crassipes can form small colonies, "floating islands" or

extensive mats that can cover thousands of hectares of previously open water It blankets

large waterbodies, creating impenetrable barriers and obstructing navigation (Gowanloch

and Bajkov, 1948; Zeiger, 1962). Floating mats block drainage, causing flooding or

preventing subsidence of floodwaters. Large rafts accumulate where water channels

narrow, sometimes causing bridges to collapse. Waterhyacinth hinders irrigation by

impeding water flow, by clogging irrigation pumps, and by interfering with weirs

(Penfound and Earle, 1948). Multimillion-dollar flood control and water supply projects

can be rendered useless by waterhyacinth infestations (Gowanloch and Bajkov, 1948).

Infestations block access to recreational areas and decrease waterfront property values, oftentimes

harming the economies of communities that depend upon fishing and water sports for revenue.

Shifting waterhyacinth mats sometimes prevents boats from reaching shore, trapping the occupants

and exposing them to environmental hazards (Gowanloch and Bajkov, 1948; Harley, 1990).

Waterhyacinth infestations intensify mosquito problems by hindering insecticide applications,

interfering with predators, increasing habitat for species that attach to plants, and impeding runoff

and water circulation (Seabrook, 1962). The hyacinth also increases evapotranspiration well above

that of open water and causes significant water loss to reservoirs and wild waters. The crowding of

plants at the edges of water bodies prevents peoples' access to the water for, e.g., collecting water

and fishing as well as access of fishing boats. While widespread, it tends only to become invasive

when there is some alteration to a water system.

5.12.7. Ecological damage: Ecological studies carried out to assess Eichhornia crassipes’s

impact on the phytoplankton community diversity established that it has serious ecological

consequence on the phytoplankton community assemblage and caused drastic reduction on the

diversity and density. Phytoplanktons play a key role in wastewater purification process (Otieno,

2003). Water hyacinth prevents sunlight and oxygen from reaching the water column and

81

submerged plants. Its shading and crowding of native aquatic plants dramatically reduces

biological diversity in aquatic ecosystems (IUCN, 2003). When invasive, water hyacinth forms a

complete covering of the water surface that excludes most light and air for submerged organisms

thus depriving them of essentials for survival Dense mats reduce light to submerged plants, thus

depleting oxygen in aquatic communities (Ultsch, 1973). The resultant lack of phytoplankton

(McVea and Boyd, 1975) alters the composition of invertebrate communities (O’Hara, 1967;

Hansen et al., 1971), ultimately affecting fisheries. Drafting mats scour vegetation, destroying

native plants and wildlife habitat. Waterhyacinth also competes with other plants, often displacing

wildlife forage and habitat (Gowanloch, 1944). Higher sediment loading occurs under

Waterhyacinth mats due to increased detrital production and siltation. Herbicidal treatment or

mechanical harvesting of Waterhyacinth often damage nearby desirable vegetation. Holm et al.

(1969) ascribed losses of $43 million in 1956 to Waterhyacinth infestations in Florida, Mississippi,

Alabama, and Louisiana.

5.12.8. Management or Control: Water hyacinth can be controlled by mechanical means

(using manpower and machines) but this is mostly unsuccessful as the plant grows faster than

mechanical clearance can keep up with. Various herbicides are effective but have significant risks

for other wetland biodiversity. Most successful and self-sustaining is biological control using two

beetles (the weevils Neochetina eichorniae and N. bruchi) and other species such as a moth, a mite

and pathogenic fungi. Biocontrol alone, however, is not always effective and there are often good

reasons for using integrated control involving mechanical and chemical control as well (IUCN,

2003).

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Fig: Eichhornea/Pistia

5.13. Waterlettuce (Pistia stratiotes)

Family: Araceae

5.13.1. Introduction: Waterlettuce is among the world’s worst weeds (Holm et al.,

1977). It is one of the worlds 100 most invasive plants.

5.13.2. Description: Waterlettuce is a perennial herb in the aroid family (Araceae).

The plant consists of free-floating rosettes of many leaves. The rosettes occur singly or

connected by short stolons. Leaves are gray-green, densely pubescent, and wedge shaped

(obovate-cu-neate). They have conspicuous parallel veins. Roots are numerous and

feathery. The inflorescences pale-green spathes near the center of the rosette. Pistia is a

monotypic in the subfamily Aroideae (Grayum, 1990). The rosettes are perennial along

the Gulf Coast, but act as annuals in more temperate zones. Population expansion is

83

primarily by vegetative propagation. It reproduces through flowers and seeds (which can

remain viable for up to 15 years) and by vegetative propagation from its stolons.

Flowering occurs year-round but peaks during summer and early autumn. Plants may be

found floating singly or in small groups or large mats - on open water or partly" stranded"

on the margins of a water body or wetland.

5.13.3. Origin: Widespread in the tropics and sub-tropics but probably originating in

South America; some authors suggest that it is native to Africa, others that it has become

"naturalised". Nevertheless it can become invasive in the true sense of that word. (IUCN, 2003)

5.13.4. Habitat: P. stratiotes is found in ponds, dams, lakes, rivers and a range of

permanent and seasonal wetlands. It often grows and expands in pools and wetlands

associated with river systems and then is released into the main river channel when the

river rises in its flood season.

5.13.5. Pathway: Water lettuce is spread along water systems by flow and wind and

can be moved by aquatic animals (hippos, other marsh mammals, waterbirds) and human

visitors to infested waters. Pistia is also moved on boats and wheeled vehicles that have

come into contact with infested waters (IUCN, 2003). It is widespread in Bangladeshi

water systems at relatively low density but can grow quickly and form mats when the

necessary nutrients are available - and in this way can become invasive

Pest status of weed: It forms extensive mats capable of blocking navigational

channels, impeding water flow in irrigation and flood control canals, and disrupting

submersed animal and plant communities (Bruner, 1982; Sharma, 1984). Water lettuce

can accumulate at barriers in flowing water and cause damage or blockage to, e.g.,

irrigation canals and inlets to hydropower installations.

5.13.6. Nature of Damage:

The economic costs associated with such damage have not been quantified. Indirect

losses accrue when large floating mats interfere with recreational activities such as boating

and fishing, but these have not been quantified. Also, several species of mosquitoes that

breed on Waterlettuce are important vectors of malaria, encephalitis, and filariae

(Lounibos and Dewald, 1989; Lounibos et al., 1990). Equine encephalitis, also vectored by

mosquitoes associated with Waterlettuce. Costs associated with these diseases are

unknown and the protin of mosquito control operations directed toward Waterlettuce-

borne mosquitoes has not been reported.

84

5.13.7. Ecological damage: It can grow together with Water Hyacinth and Salvinia to

worsen the effects of both. There are reports of deleterious ecological impacts associated

with P. stratiotes infestations and these studies have generally been limited in scope.

Sculthorpe (1967), for instance, noted that the intertwined root systems (composed of long

adventitious roots arrayed with copious lateral rootlets) of extensive infestations accelerate

siltation rates as they slow water velocities in rivers and streams. The resultant degradation

of benthic substrates under these infestations has never been studied directly, but

accelerated siltation often renders the affected benthos unsuitable as nesting sites for

various fish species (Beumer, 1980) and as macroinvertebrate habitat (Roback, 1974). The

accumulation of Waterlettuce-generated detritus under large infestations only adds to this

problem, and likely increases sediment and nutrient loadings much as it does under

waterhyacinth mats (Schmitz et al., 1993). Furthermore, Sridhar (1986) reports that

Waterlettuce can bioaccumulate considerable amounts of heavy metals, so the detritus

under some mats could be toxic. The waters under dense Waterlettuce populations in lakes

can become thermally stratified (Sculthorpe, 1967; Attionu, 1976), with dissolved oxygen

levels and increased alkalinity (Yount, 1963; Attionu, 1976; Sridhar and Sharma, 1985).

Prolonged oxygen deficits reduce plankton abundance (Hutchinson, 1975) and cause

increased morality of fish (Ayles and Baricaa, 1977; Clady, 1977) and macrovertebrates

(Roback, 1974; Cole, 1979). Summary can be written as:

Water-lettuce mats can lower dissolved oxygen concentrations reducing aquatic

life.

Dense populations may lower water levels because water-lettuce increases

evaporation rates over open water areas.

Water-lettuce mats can restrict water flow increasing flooding along rivers and

canals.

Dense water-lettuce populations produce ideal breeding environments for

mosquitoes.

Water-lettuce populations crowd out native plants and animals (lowers

biodiversity).

Water-lettuce populations often form large expanses of dense, impenetrable

floating mats limiting boat traffic, recreation, flood control, and wildlife use. These dense

canopies at the water surface shade out native submersed plant species and can uproot

native emergent plants that are important to wildlife. P. stratiotes can form thick and

extensive mats that can block both sunlight and air from reaching a water surface and so

have impacts on aquatic biodiversity and fisheries.

85

5.13.8. Management/Control: Pistia can be controlled by the mechanical removal of

plants - but care must be taken that they are not re-introduced to the water system.

Chemical control has been used and 2-4 D, a herbicide is quite effective - except for the

obvious impacts on non-target species in wetlands and water bodies. Biological control

using beetles (especially the weevil Neohydronomous affinis) has been effective in tropical

situations. As with other floating aquatic weeds, however,care taken with the watershed to

reduce nutrient input to wetlands is the most effective method of control -a I t h o u g h

expensive and not always possible. (IUCN, 2003)

Chapter 6: Control and management

of IAS.

6.1 Control of invasive plants.

Biological invasions pose a huge nationwide and worldwide problem that urgently

needs innovative approaches toward solutions (Philip and Lloyd, 2001). Indeed, no

agency can hope to rid their lands of hundreds of years of nonnative introductions

(Akerson, 2003). In response to the expanding ranges of and increasing damage caused by

alien species, the control of invasive alien species has become a priority for environmental

management and an integral component of many habitat conservation efforts. Alien

species damage native species and ecosystems on a global scale. Thus, to prevent further

loss of biological diversity, we need to study and control the spread of alien species as

quickly as possible. Most alien species have not been sufficiently investigated with respect

to effective countermeasures to prevent their intrusion and expansion (Primack & Kobori,

1997). In order to take prompt measures against ecological problems of invasive alien

species (IAS), we have to own jointly biological data, which indicate the IAS species

identification, the origin of the IAS, the process of invasion of the IAS, and the ecological

impact caused by the IAS (Koich et al. 2004)

Invasive plants pose a major threat to the productivity and sustainability of

agricultural, managed and natural ecosystems. Thus, invasive plants are biological

86

pollutants within infested ecosystems. Unlike chemical pollutants that diminish over time,

biological pollutants have the ability to grow adept, reproduce and spread, unless

mitigated.

6.1.1. Control methods can include the following or a combination of all

four:

6.1.1.1 Chemical control:(using pesticides) can be effectively used to destroy

invasive species, but it can be problematic due to impacts on non-target organisms

(including humans), the development of resistance, and expense,

6.1.1.2 Physical/ Mechanical control: Means either hand pulling or temporarily

changing the environment to control invasive weeds. Temporary environmental changes

include reducing light with dyes, dewatering in the water to freeze, dry, then burn plants,

and flooding to shade underwater plants or flush floating plants out of the water body

(Anon, 2003). Physically removing the invasive species is often successful, but can be

expensive and labor intensive. Depending on the types of plants and conditions, many

different kinds of machines cut, chop, shred, slurry, press, transport, and remove invasive

aquatic weeds.

6.1.1.3 Biological control:(introducing a natural enemy-predator, parasite, or

disease-often from the pest’s native range) can be an environmentally sound way to

control invasive species with minimal expense, but some control agents do not survive and

others attack non-target organisms, i.e., become invasive themselves.

6.1.2. Prevention: Clearly, The best way to limit impacts of nonnative species is to

prevent them from invading and becoming established in a new area. Prevention is the best

deterrent against invasive plants. However, it is difficult to know if a species will become

a problem in a given locality and we often don't know why some species become invasive.

Sometimes species don’t pose problems until years after they’ve been in an area.

Complete removal may be feasible early in an invasion or in a restricted area, but more

often control or containment is the only practical way to limit ecological or economic

damage, especially for species that have already invaded large areas. Once established,

successful eradication or management is contingent upon early detection, identification,

assessment, development of eradication strategies and a steadfast implementation of that

strategy. Recognition of need, desire to succeed, and the willingness to persist, are key

elements of success. The most effective way to reduce invasive weed problems is to

prevent their introduction. This is much more difficult than it may seem. It is difficult to

87

predict which may become problems before they are brought into the Bangladesh. When

freed from these controls, some plants thrive and become invasive weeds in their new

surroundings. One can help prevent problems by never putting aquarium plants in lakes,

rivers, or wetlands.

6.1.3. Eradication: The eradication or successful containment and management of an

invasive plant requires a logical process to succeed. 5 fundamental steps of this process

are: 1) Recognition of need; 2) Discussion among stakeholders; 3) Development of

strategies and a course of action; 4) Development of methodology; 5) Improvements as

needed. Implementation of these seven fundamental steps, along with common sense and

persistence, will lead to a successful program (Eplee, 2003). The Witchweed eradication

Program [Striga asiatica (L.) O. Kuntze] that was initiated in the Carolinas in 1958 is a

Fig: Eichhornea crassipes(eradication)

88

case study in the successful eradication of an alien, invasive plant. This federal – state

cooperative effort utilized the seven elements of successful program implementation. After

the program began, it took nearly 20 years to develop the strategies and science based

methodologies to effectively deal with this invasive plant.

When prevention fails, eradication of invasive plants becomes the second best

alternative to control invasive plants. Most of the invasive herbs and shrubs like Lantana

camara, Eupatorium odoratum, Ipomea carnea, Mikania cordata, Ageratum conyzoides,

Imperata cylindrica, Eichhornea crassipes, Pistia stratiotes, etc. are physically eradicated

by the farmers in Bangladesh.

6.1.3.1. Criteria to be satisfied to achieve Eradication:

Shine et al. (2000) gave some conditions to be satisfied to Achieve Eradication which are

as follows:

a. The rate of population increase should be negative at all densities. At very low

densities it becomes progressively more difficult and costly to locate and remove

the last few individuals.

b. Immigration must be zero. This is usually only possible for offshore or oceanic

islands, or for very new alien invasions.

89

c. All individuals in the population must be at risk to the eradication technique(s) in

use.

d. The survival of seed banks in the soil should be checked.

e. Adequate funds and commitment must continuously exist to complete the

eradication over the time required. Monitoring must be funded after eradication is

believed to have been achieved until there is no reasonable doubt of the outcome.

f. The socio-political environment must be supportive throughout the eradication

effort. Objections should be discussed and resolved, as far as practicable,

before-the eradication begun.

6.1.4. Early Detection and Rapid Response:

Once invasive weeds become widely dispersed within a water body or across a

large region, eradicating them becomes difficult and often impossible. Ecosystem

managers/Foresters should frequently inspect lands/waters for known invasive weeds and

to find plants that do not seem to belong. When invasive weeds are discovered,

management programs must begin immediately to reduce environmental damage and

economic costs.

6.1.5. Slowing the spread: Invasive species spread in many ways, often helped

unintentionally by people. One can slow the spread of invasive species, and prevent new

invasions, by being an aware, responsible and vocal steward of one’s own property.

Scout for invasive plants: we have to learn which plants and animals are problems

in Bangladesh, so they can be recognize if they are see them.

Remove invasive plants before they become a problem: The best way to control

invasives is through early detection and rapid response. we should pull, cut, spray

or deadhead problem plants before they go to seed.

Avoid introducing invasive plants: Checking with plant sellers home and abroad

before buying plants can be made, to make sure that the plant wanted, whether

native or exotic, is not invasive.

90

Avoid transporting invasive plants: Seeds of invasive plants are easily moved from

place to place on hiking boots, car tires, pants cuffs, and camping or recreational

gear, especially when entering wildlands or other natural areas, or new bodies of

water. We should not bring species into Bangladesh from distant parts of the

world.

Minimize disturbance: Many invasive plants, are adapted to disturbance and

rapidly take over newly disturbed areas. We should monitor disturbed areas for

species that spread quickly.

Spread the word: we should Spread the word Invasive plants that have

environmental, economic and social impacts for all of us to the common people,

appropriate state government agencies and conservation groups (Anon, 2003).

6.2. Control of invasive aquatic weeds:

Because water is so important to our survival, scientists and ecosystem managers

continually search for additional and more effective ways to control invasive aquatic

weeds while preserving native plants and animals and protecting human health and

property. Invasive aquatic weed control methods fit into any of the four basic categories

described earlier:

Aquatic plant managers combine, or integrate, (Integrated plant management) as

many different methods as possible to control invasive weeds. There is to reduce problems

from invasive weeds and improve conditions for native plants and animals using the

control methods that are best suited to conditions in and surrounding each water body.

Water hyacinth control is a good example of integrated plant management. Several insects

and diseases feed only on water hyacinth reducing plant size and the amount of seeds it

produces. This reduces the amount, and also the cost, of herbicides needed to control water

hyacinth. Mechanical harvesters remove water hyacinth from small areas where herbicides

are not practical or if immediate removal is needed like dams and bridges. Sometimes,

water hyacinth is piled up by picking and allowed to rot or burnt when dried.

91

6.3. The strategy of managing exotic invasive plants:

The goals of alien species management include eradication, control and

confinement however; the first is the ideal solution (Nobuo and Mick, 2004). The invasion

of exotic plants is a severe problem due to its tremendous damage and impact. The

management and assessments of exotic plants are so very important. In fact, introduced

species are a greater threat to native biodiversity than pollution, harvest, and disease

combined (Pokorny et al., 2003). Thus, the practical and effective ways and means of

stopping or reducing invasions are in an urgent need.

Mechanical methods are only used at the starting of invasion or small number of

non- native species appearing.

Chemical means can cause new environmental problem that can bring new

pollution and threats to other native species.

Biological control is the science and technology of controlling pests and other

dangerous species by using natural enemies. There have been many successful cases in the

field of using biocontrol. However, biocontrol is not a panacea. Without careful use, it can

produce threats to non-target species. This indicates that a more thorough screening

biocontrol agents for non- native species should have preceded the release of these agents

(Wang and Meijuan, 2003).

To manage non-indigenous plant invasions, mechanisms of invasion resistance

must be identified and modified as a portion of management. One mechanism is that

functionally diverse plant assemblages use resources more completely. Study suggested

that establishing and maintaining a diversity of plant functional groups within the

community enhances resistance to invasion (Pokorny et al., 2003). A generalized objective

for invasive plant management is to establish and maintain invasion resistant plant

communities that meet other land-use objectives. Establishing and maintaining diverse,

weed resistant plant communities must be a major goal of all integrated weed management

programs (Pokorny et al., 2003).

Successful management of invasive plants requires active attempts to prevent new

introductions, vigilant detection of nascent populations, and persistent efforts to control

and eradicate the worst exotic weeds. To achieve these objectives, Rejmanek, (2003) gave

five groups of complementary approaches. (1) Stochastic approaches allow probabilistic

92

predictions about potential invaders based on initial population size, residence time, and

number of introduction attempts. (2) Empirical taxon-specific approaches are based on

previously documented invasions of particular taxa. (3) Evaluations of the biological

characters of non-invasive taxa vs. those of successful invaders give rise to both general

and habitat-specific screening procedures. (4) Evaluation of environmental compatibility

helps to predict whether a particular plant taxon can invade specific habitats. Finally, (5)

experimental approaches attempt to tease apart intrinsic and extrinsic factors underlying

invasion success. An emerging theory of seed plant invasiveness based on biological

characters has resulted in several rather robust predictions. Population fitness homeostasis,

as a result of both individual fitness homeostasis and population genetic polymorphism, is

a general prerequisite invasiveness over a range of environments. While several characters

linked to reproduction and dispersal are best predictors of invasiveness disturbed habitats,

competitiveness for limiting resources promotes invasiveness in natural and semi-natural

ecosystems (Rejmanek, 2003).

Invasive plants impede grassland restoration by disrupting ecosystem processes.

Managing invasive plants requires manipulating disturbance regimes that favor desirable

species and wanted changes in successional trajectories. Reasons for the arrival,

establishment and spread of invasive plants should be understood before effective

grassland restoration strategies are developed. Removing an invasive plant species without

attention to plant community dynamics often only opens niches for other undesirable

species to occupy. The suitability of weed control tools (biological, chemical, mechanical

and cultural) will vary according to the invasive plant and

invaded site characteristics (Masters and Daniel, 2003).

For invasive plant control to be effective, citizen involvement is key. Linking local

issues with parallel regional, national and global ones can accomplish this task. The broad

need to conserve native biodiversity worldwide should be articulated to a specific

community in local terms, with local issues, such as controlling Kachuripana (Eichhornea

crassipes). To truly arouse human interests and meet human needs, successful

demonstration projects should be implemented and marketed so that individuals can

physically see how the recreational experience improves in absence of adjacent

monocultures and how property values rise where a diversity of native species have

regenerated (Sewak and Kylie, 2003).

93

Once the invasive species have been controlled or eliminated, ecosystems may

need to be restored to return lost components or functions to degraded areas. Restoring

native communities is an important step to minimize the chances an area will be

reinvaded.

94

Part 3: Field observations

Chapter 7: Materials and Method

7.1. Materials and Method:

7.1.1 Collection of information: Literatures were collected from the

published books, journals, weeklies, thesis and review papers or other scientific writings

from the libraries of different universities and research Institutions. Internet was one of the

important sources of literature. Consultation was made to the experts (Botanists,

Silviculturists, Zoologists, Foresters) of various Institutes and informations were written

down. Related information were also collected form various Project experts of various

agencies like Forest Department, IUCN, UNEP etc. working for the conservation of

Biodiversity in Bangladesh.

7.1.2. Method applied: The research work method included taking of 2m by

2m sample plots randomly one under alien species (Acacia auriculiformis, Eucalyptus

camaldulensis and Melaleuca leucadendron) and another under adjacent indigenous trees,

separately for each of these three trees, whatsoever indigenous trees are present very close

to the alien species plantation. Each of these two sample plots formed 1 replication. There

were 4 replications taken for each alien species in different part of Chittagong and Sylhet.

Name (scientific or local or both), total no and average height of the undergrowth plants

were taken from adjacent random sample plants of 2m by 2m size under alien trees and

nearby indigenous trees separately. Careful selection of the site was made where there

exist both alien and indigenous trees in nearby plantation. In the hills sample plots under

alien trees and nearby indigenous trees were selected taken at similar slope, altitude and

aspect. 4 replications were taken for each invasive tree species, 3 in Chittagong and 1 in

Sylhet. Each replication included 2 sample plots one under alien tree and another under

indigenous trees.

For Lantana camara, Eupatorium odoratum, Mikania cordata, and Ipomea carnea,

2m by 2m sample plots were taken and the plants growing with them in close association

or contiguous to the invasive plants were noted down. Growth of these species was

95

measured from periodic evaluation from the sample plots that were guarded in wild

condition in Chittagong and Sylhet. Their impact on nearby plants was observed by

visiting different localities of Bangladesh.

The samples that could not be identified instantly was collected and later taken to

the experts for identification and properly identified by their local name, scientific name,

and family they belong to.

The spread or distribution of the invasive plants was estimated through physical

visit to different localities in Bangladesh. Photographs of invasive plants species were also

taken.

7.1.3. Materials used: Sunto clinometer was used to measure the height of the

trees, slope and altitude of the sample plots. Diameter tape was used for diameter

measurement of the trees. Measuring tape was used to fix the sample size in the field.

Wooden scale of 1m height graduated in cm was used to measure the undergrowth height

and growth. For undergrowth vines e.g. Alulata, Asamlata etc, their length, horizontal or

vertical, has been considered as height in this literature

7.1.4. Compilation of data: Finally all the data was compiled to generate

information and the thesis was written down.

96

7.2. Rationale of the method applied in this research work:

In attempting to assess the direct effects of invasive plants on local native species

diversity, the easiest way to interpret the effect would be experimental introductions of

alien plants into native communities. But an alternative experimental approach to

assessing the impacts of invaders on native plant diversity is to physically remove alien

vegetation from a site and quantify changes in diversity that follow but is very labor

intensive. Easiest quantitative evidence for the loss of biodiversity due to invasive plants

comes from paired community surveys, where native species abundance, richness or

diversity is compared between invaded and a neighboring univaded areas. (Holms and

Cowling, 1997a; D’Antonio et al., 1998)

The latest methodology was applied in this work. The research method applied to

assess the impact of invasive plants on native plant biodiversity in Bangladesh included

taking of 2m by 2m sample plots randomly one under alien species (Acacia auriculiformis,

Eucalyptus camaldulensis and Melaleuca leucodendron) and another under adjacent

indigenous trees, whatever indigenous trees are present very close to the invasive species

plantation. Each of these two sample plots formed one replication. The sample plots in

each replication were not wide apart. In most of the cases, they were on average within 15

m apart. The shorter distance of sample plots are expected to eliminate the experimental

error roughly. All sample plots of each replication are selected carefully so that they

belong to the same slope, altitude and aspect of the slope to reduce the microclimate effect

on the growth of the ground vegetation. Nutrient status, microbial effect, biotic effects etc

on the growth of vegetation of each sample plot were considered negligible or similarly

effected. The vegetation structure and undergrowth were considered only be affected by

alien and indigenous trees.

97

Chapter 8: Result and

Discussion

8.1. Data of the sample plots in Acacia auriculiformis,

Eucalyptus Camalsulensis, and Melaleuca leucodendron

plantations.

8.1.1. Sample plots in Acacia auriculiformis and indigenous trees

plantations:

Replication 1:

Location: Lower hill slope in front of the administrative building of the Institute of

forestry and environmental sciences, Chittagong University.

Slope: 24%

Altitude: 2m from the ground level.

Spacing: For both Acacia auriculiformis and indigenous species is 2mx2m

Age: 11 years for both Acacia auriculiformis and indigenous trees plantation.

Distance: between the sample plots of Acacia auriculiformis and indigenous trees

plantation is 9m.

Average height of Acacia auriculiformis: 12m

Average diameter of Acacia auriculiformis: 11.5cm

Average height of indigenous trees (Telsur- Hopea odorata and Chickrassy- Chickrassia

tabularis): 10m

Average diameter of indigenous trees: 8.5cm

Table 3: Name of the plant species found in the sample plots under Acacia

auriculiformis and indigenous trees with their total number and average

height in replication 1.

Species name

Under Acacia

auriculiformis

Under

Indigenous tree

Local Name Scientific Name Family

Total

no

Avg.

ht

(c m)

Total

no

Avg

ht

(cm)

Ageratum conyzoides Compositae ** ** 3 23

98

Derris spp Leguminosae ** ** 2 56

Polygonum spp ** ** 11 48

Aal gash 45 27 48 27

Apang Nelsonia spp Acanthaceae 4 57 6 27

Arkila Ixora nigricans Rubiaceae 6 45 6 45

Arshogonda Withania somnifera ** ** 1 22

Asamgash Eupatorium odoratum Compositae 1 25 3 25

Bash ghass Graminae ** ** 3 86

Chotrapata Flaria interapta Articaceae 4 8 5 8

Golboroi/

Jongliboroi

** ** 2 53

Kaispata Dalbergia stipularis Leguminosae 5 47 8 47

Sample -1 3 54 ** **

Sample -2 1 56 2 50

Toynlata Jasminum spp Oliceea 5 72 6 72

Vitex Clerodendrum viscosum Verbenaceae 1 15 3 15

** Indicates that the species is absent to that plot.

Replication 2:

Location: Mid hill slope at the back of the under construction auditorium of Shahjalal

University of Science and Technology, Sylhet.

Slope: 35%

Altitude: 5m from the ground level.

Spacing: 2mx2m for both Acacia auriculiformis and indigenous species

Age: 16 years for both Acacia auriculiformis and indigenous trees plantation.

Distance: between the sample plots of Acacia auriculiformis and indigenous trees

plantation is 9m.

Average height of Acacia auriculiformis: 18m

Average diameter of Acacia auriculiformis: 16.5cm

Average height of indigenous trees (Chapalish- Artocarpus chaplasha, Arjun- Terminalia

arjuna and others): 15m

Average diameter of indigenous trees: 16.2cm

99

Table 4: Name of the plant species found in the sample plots under Acacia

auriculiformis and indigenous trees with their total number and average

height in replication 2

Species name

Under Acacia

auriculiformis

Under Indigenous

tree

Local

Name

Scientific Name Family

Total

no

Avg.

ht

(c m)

Total

no

Avg

ht

(cm)

Borreria articulark Rubiaceae 2 63 2 61

Commelina spp. Commelinaceae 5 48 6 51

Ichnocarpus frutescens

Apocynaceae 5 38 5 42

Polygonum spp 3 40 3 53

Achargash Microcos paniculata Tiliaceae 1 60 1 60

Bas gassh Graminae 1 45 1 45

Ghuruchea Combritum spp Combretacea 8 50 8 50

Gulboroi/Jo

ngli boroi

Zizyphus oenoplea Rhamnaceae 1 15 1 15

Kaispata Dalbergia stipularis Leguminosae 2 40 2 40

Putijam Syzygium cumini Myrtaceae 2 45 2 45

Sample 1 3 25 3 25

Sample-3 2 45 2 49

Ulu son Saccharum

spontaneum

Cramineae 15 65 18 71

Umberalla

Boewia spp. 1 72 1 58

Vitex Clerodendrum

viscosum

Verbenaceae 2 32 2 32

Zongli

jumka/Jumkalata

Passiflora foetida Passifloraceae 1 120 2 116

Piper

boehmerifolium

Piperaceae ** ** 1 35

Khosh khoshia lata Byttneria pillosa Sterculiaceae ** ** 2 90

Muschanilata Stephania

harnendifolia

Menispermaceae ** ** 1 75

100

Sample-4 ** ** 1 35

** Indicates that the species is absent to that plot.

Replication 3:

Location: Chittagong University Campus. Mid hill slope near the Social Science

Building.

Slope: 42%

Altitude: 6m from the ground level.

Spacing: 1.5mx1.5m for both Acacia auriculiformis and indigenous species

Age: 15 years for both Acacia auriculiformis and indigenous trees plantation.

Distance: between the sample plots of Acacia auriculiformis and indigenous trees

plantation is 8m.

Average height of Acacia auriculiformis: 16m

Average diameter of Acacia auriculiformis: 17cm

Average height of indigenous trees (Gargan -Dipterocarpus turbinatus and Gamar -

Gmelina arborea, Pitraj -Aphanamixis polystachya): 14.5m

Average diameter of indigenous trees: 15.2cm

Table 5: Name of the plant species found in the sample plots under Acacia

auriculiformis and indigenous trees with their total number and average

height in replication 3.

Species name

Under Acacia

auriculiformis Under Indigenous

tree

Local Name Scientific Name Family

Total

no

Avg.

ht

(c m)

Total

no

Avg

ht

(cm)

Achargash Microcos paniculata Tiliaceae 3 65 4 110

Alulata Dioscorea alata

Discoriaceae 2 100 2 300

Arkila Ixora nigricans Rubiaceae 5 63 8 20

Asamgash Eupatorium odoratum Compositae ** ** 4 15

Bashker 40 35

Batna Quercus spicata ** ** 5 100

Dumur Ficus hispida Moraceae ** ** 1 62

101

Ghuruchea Combritum spp Combretacea 6 80 12 130

Gulboroi/Jongli

boroi

Zizyphus

oenoplea

Rhamnaceae 1 25 ** **

Hara ** ** 1 400

Horina

/Horinna Gota

Vitex

peduncularis

Verbenaceae ** ** 3 90

Jharugash Thysaenolena

maxima

Poaceae 8 90 ** **

Kaispata Dalbergia stipularis Leguminosae ** ** 4 60

Khosh khoshia lata Byttneria pillosa Sterculiaceae 1 45 ** **

Lantana Lantana camara Verbenaceae ** ** 7 110

Maittalata ** ** 1 80

Malastoma /Indian

Rhododendron

Melastoma

malabathricum

Melastomataceae 2 100 4 80

Putijam Syzygium cumini Myrtaceae 1 15 1 150

Sample 1 ** ** 5 150

Sample 2 1 36

Sample 2 ** ** ** **

Sercuti Phyllanthus spp. Euphorbiaceae ** ** 1 120

Shialkata Cnicus arvensis Compositae ** ** 1 350

Tagar Tabernaemontana

divericata

Apocynaceae ** ** 1 90

Vitex Clerodendrum viscosum Verbenaceae 4 70 4 100

** Indicates that the species is absent to that plot.

Replication 4:

Location: Chittagong University Campus. Mid hill slope near the security office.

Slope: 20%

Altitude: 4m from the ground level.

Spacing: 2mx2m for both Acacia auriculiformis and indigenous species

Age: 14 years for both Acacia auriculiformis and indigenous trees plantation.

102

Distance: between the sample plots of Acacia auriculiformis and indigenous trees

plantation is 8m.

Average height of Acacia auriculiformis: 15m

Average diameter of Acacia auriculiformis: 16.5cm

Average height of indigenous trees (Jarul -Lagerstroemia speciosa,Gargan -Dipterocarpus

turbinatus, Chapalish- Artocarpus chaplasha): 13m

Average diameter of indigenous trees: 15.5cm

Table 6: Name of the plant species found in the sample plots under Acacia

auriculiformis and indigenous trees with their total number and average

height in replication 4.

Species name

Under Acacia

auriculiformis

Under

Indigenous tree

Local Name Scientific Name Family

Total

no

Avg.

ht.(c m) Total no

Avg

ht. cm)

Lygodium flexuosum Schiziaceae ** ** 1 40

Wikestoemia spp Wikestomiaceae 1 45 1 49

Achargash Microcos paniculata Tiliaceae 7 100 6 80

Arkila Ixora nigricans Rubiaceae ** ** 10/

12

20

Arshogonda Withania somnifera 3 70 1 120

Asamlata Eupatorium

odoratum

Compositae 5 120 1 130

Batna Quercus spicata 1 70 ** **

Ghuruchea Combritum spp Combretacea 12 60 ** **

Goda Vitis glabrata

1 40 ** **

Gondaraj Gardenia grandiflora Rubiaceae 7 60 ** **

Horina

/Horinna

Gota

Vitex peduncularis Verbenaceae ** ** 2 60

Jharugash Thysaenolena

maxima

Poaceae 3 50 4 80

103

Lantana Lantana camara Verbenaceae ** ** 1 120

Malastoma

/Indian

Rhododendron

Melastoma

malabathricum

Melastomataceae ** ** 3 80

Meda 1 40 ** **

Narisa Polygonum spp Polygonaceae ** ** 2 39

Pitali ** ** 1 70

Pitraj Aphanamixis

polystachya

Meliaceae 1 75 1 79

Putijam Syzygium cumini Myrtaceae 2 80 5 90

Sample 5 1 bunch 115 1 120

Sample 6 2 20 2 30

Sample 7 ** ** 3 150

Shialkata Cnicus arvensis Compositae 2 11 ** **

Sullia kata Xanthium indicum Compositae 2 90 2 102

Tagar Tabernaemontana

divericata

Apocynaceae ** ** 1 100

Toynlata Jasminum spp Oliceea ** ** 2 120

Vitex Clerodendrum viscosum Verbenaceae 3 60 4 60

** Indicates that the species is absent to that plot.

Table 7: Tabulation of total number of plants (herbs, shrubs and tree

seedlings) found in all sample plots of Sylhet and Chittagong

under indigenous trees and Acacia auriculiformis with

their average height:

Species name

Under

Indigenous

trees

Under Acacia

auriculiformis

Local Name Scientific Name Family

Total no

Avg.

ht (c m) Total

no

Avg.

ht (cm)

Ageratum conyzoides Compositae 3 23 ** **

Borreria articularis

Rubiaceae 4 61 ** **

Commelina spp. Commelinaceae 5 51 ** **

104

Derris spp 2 36 ** **

Ichnocarpus frutescens

Apocynaceae 5 42 ** **

Lygodium flexuosum Schiziaceae 1 40 ** **

Piper boehmerifolium Piperaceae 1 35 ** **

Polygonum spp 14 50.5 ** **

Wikestoemia spp Wikestomiaceae 1 45 ** **

Achargash Microcos paniculata Tiliaceae 11 83.33 11 75

Algash 48 27 ** **

Alulata Dioscorea alata

Discoriaceae 2 300 2 100

Apang Nelsonia spp Acanthaceae 6 57 ** **

Arkila Ixora nigricans Rubiaceae 24 28.33 ** **

Arshogonda Withania somnifera 2 71 3 70

Asamgash Eupatorium odoratum Compositae 7 20 ** **

Asamlata Mikania cordata Compositae ** ** 3 120

Bash ghass Graminae 4 65.5 41 40

Batna Quercus spicata 6 115 1 70

Chotrapata Flaria interapta Articaceae 5 8 4 50

Dumur Ficus hispida Moraceae 1 62 ** **

Ghuruchea Combritum spp Combretacea 20 72.5 26 63.3

3

Goda ** ** 1 40

Golboroi/Jon

gliboroi

3 15 2 20

Gondaraj Gardenia grandiflora Rubiaceae ** ** 7 60

Hara 1 400 ** **

Horina

/Horinna

Gota

Vitex peduncularis Verbenaceae 5 75 ** **

Jharugash Thysaenolena maxima Poaceae 5 115 11 70

Jongliboroi 2 53 ** **

Kaispata Dalbergia stipularis Leguminosae 14 51.75 7 43.5

Khosh Byttneria pillosa Sterculiaceae 2 90 1 45

105

khoshia lata

Lantana Lantana camara Verbenaceae 8 115 ** **

Maittalata 1 80 ** **

Malastoma /Indian

Rhododendron

Melastoma

malabathricum

Melastomataceae

7 80 2 100

Meda ** ** 1 40

Muschanilata Stephania

harnendifolia

Menispermaceae 1 75 ** **

Narisa Polygonum spp Polygonaceae 2 39 ** **

Pitali 1 70 ** **

Pitraj Aphanamixis polystachya Meliaceae 1 74 1 75

Putijam Syzygium cumini Myrtaceae 8 95 5 46.66

Sample 1 8 87.5 6 39.5

Sample 2 2 50 1 56

Sample 3 2 49 2 45

Sample 4 1 35 ** **

Sample 5 1 120 1 115

Sample 6 2 30 2 20

Sample 7 3 150 ** **

Sercuti Phyllanthus spp. Euphorbiaceae 1 120 ** **

Shialkata Cnicus arvensis Compositae 1 350 2 11

Sullia kata Xanthium indicum Compositae 2 102 2 90

Tagar Tabernaemontana

divericata

Apocynaceae 2 95 ** **

Toynlata Jasminum spp Oliceea 8 72 5 72

Uluson Saccharum spontaneum Cramineae 15 71 15 65

Umbrella 1 58 1 72

Vitex Clerodendrum viscosum Verbenaceae 13 51.75 10 44.25

Zongli

jumka/Jumkalata

Passiflora foetida Passifloraceae 2 116 1 120

106

Table 7 shows, in all plots of Sylhet and Chittagong, 52 species were found under

indigenous trees and 30 species were found under Acacia auriculiformis. 22 more species

was found under indigenous trees, which were absent under Acacia auriculiformis. In

most of the cases the average number of plants and their average height in sample plots of

indegenous trees are higher than that of plots under Acacia auriculiformis.

Major 10 species found under indegenous trees in maximum number and frequency is

Algash, Arkila (Ixora nigricans) Ghuruchea (Combritum spp) Ulusom (Saccharum

sportaneum) Kaispata (Dalbergia stipularis) Vitex (Clerodendrum viscosum) Achargash

(Microcos paniculata) Lantana (Lantana camara) Putijam (Syzygium cumini) and sample

1 respectively.

Major 10 species found under Acacia auriculiformis in maximum number and

frequency are Bashghass, Ghuruchea (Combritum spp), Uluson (Saccharum sportaneum),

Achargash (Microcos paniculata), Gharugash (Thysaenolena maxima), Vitex

(Clerodendrum viscosum), Gondaroj (Gardenia gardiflora), Kaispata (Dalbergia

stipularis), sample 1 and Putijam (Syzygium cumini) respectively.

Major10 species with maximum height found under indigenous tree species Hara,

Shialka (Cricus arvensis), Alulata (Dioscorea alata) sample 7, sample 5, Sercuti

(Phyllanthus spp), Jumkalata (Passiflora foetida), Gharugas (Thysaenolena maxima),

Batra (Quercus spicata) and Lantana (Lantana camara) respectively.

Major10 species with maximum height found under Acacia auriculiformis are

Asamlata (Mikania cordata), Jumkalata (Passiflora foetida), sample 5, Alulata (Dioscorea

alata), Melastoma (Melastoma malobathricum), Sulliakata (Xanthiun indicum), Achargash

(Microcos paniculata), Pitraj (Aphanamixis polystachya), Toynlata (Jasminum spp), and

Umbrella.

Comparison can be made in terms of the total number and average height of the

undergrowth species (Table 7) found under indigenous tree with that of Acacia

auriculiformis which are present in sample plots both under indigenous trees and Acacia

auriculiformis. For better understanding topmost 5 common undergrowth species are

compared in term of their maximum total number found under indigenous trees with that

of under Acacia auriculiformis. The 5 topmost species are Ghuruchea (Combritum spp),

Uluson (Saccharum sportaneum) Kaispata (Dalbergia stipularis) Vitex (Clerodendron

viscosum) and Achargash (Microcos paniculata).

107

The total number and average height of Ghuruchea (Combritum spp) under

indigenous tree are 20 and 72.5 cm respectively. While the figure under Acacia

auriculiformis are 26 and 63.33 respectively.

The total number and average height of Uluson (Saccharum sportaneum) under

indigenous tree are 15 and 71 cm. While the figure under Acacia auriculiformis are 15 and

65 cm respectively.

The total number and average height of Kaispata (Dalbergia stipularis) under

indigenous tree are 14 and 51.75 cm respectively. While the figure under Acacia

auriculiformis are 7 and 43.5 cm respectively.

The total number and average height of Vitex (Clerodendron viscosum) under

indigenous tree are 13 and 51.75 cm respectively. While the figure under Acacia

auriculiformis are 10 and 44.25 cm respectively.

The total number and average height of Achargash (Microcos paniculata) under

indigenous tree are 11 and 83.33 cm. While the figure under Acacia auriculiformis are 11

and 75 cm respectively.

Of these 5 species, when compared the figure of total number and average height

(Table 7) of species found under indigenous trees with that under Acacia auriculiformis,

for 3 species Achargash (Microcos paniculata), Ulusom (Saccharum sportaneum),

Kaispata (Dalbergia stipularis), the total number or average height found under

indigenous trees are higher than under Acacia auriculiformis. For other 2 species

Ghuruchea (Combritum spp), Vitex (Clerodendrum viscosum), the total number and

average height under indigenous trees are lower than that of Acacia auriculiformis.

Out of these 5 species of undergrowth 3 species i.e. 60% of the undergrowth

vegetation showed better performance under indigenous trees than that of Acacia

auriculiformis. Out of these 5 species of undergrowth 2 species i.e. 40% of the

undergrowth vegetation did not show better performance under indigenous trees than that

of Acacia auriculiformis.

When compared this way, the total number and average height of the common species

of plots under indigenous trees and Acacia auriculiformis (Table 7) it can be seen that for

most of the species, the total number found in all sample plots under indigenous trees and

their average height are higher than respective figures of undergrowth vegetation found

under Acacia auriculiformis plantation.

108

8.1.1.1 Is Acacia auriculiformis invasive in Bangladesh?

The result testifies that Acacia auriculiformis affects the indigenous plant

biodiversity under it by reducing the number and growth. There is less vegetation found

under Acacia auriculiformis plantation in comparison to the open areas or under

indigenous trees. In most of the cases, soil under Acacia was found totally or partially

exposed and presence of rills and splash soil erosion that enhance top soil removal or site

degradation, of course Acacia auriculiformis can grow on degraded land and in my field

visit, I had seen clear demonstration of this.

Whether Acacia auriculiformis should be called invasive in Bangladesh or not is a

controversial issue. All Acacia auriculiformis patches found in Bangladesh are plantations

raised by different Institutions, NGOs or by public. One of the characteristics of invasive

plants is that reproduces massively and displaces native vegetation by luxuriant growth

(CBD, 2001). Natural regeneration of Acacia auriculiformis is not too much apart in

Bangladesh. All the plantations are deliberately raised and once upon a time this species

was wellcomed in Bangladesh (Das, 1986). But being established now, this species is

impacting negatively to our indigenous biodiversity. This statement is clear from the

experiment result. There was observed a reducing growth and diversity of indigenous

vegetation under Acacia auriculiformis than under indigenous trees. My personal

perception regarding the stereotyped idea that invasive species should reproduce

massively should be redefined. This Papua New Guinean tree (Das, 1986) is also blamed

not to be favoured by indigenous birds for stay. Uddin and Mohammad (2003) determined

the impacts of invasive monocultures of Acacia auriculiformis and Eucalyptus

camaldulensis and soil properties and indigenous vegetation of Bangladesh. They found

slight variation on soil properties and considerable reduction of number and density of

indigenous undergrowth vegetation per hectare under invasive monoculture in comparison

to these in natural condition. Result of my study is co-axial with this. So Acacia

auriculiformis can be termed invasive tree in Bangladesh.

109

8.1.2. Sample plots in Eucalyptus camaldulensis and indigenous

trees plantations.

Replication 1: Location: Top of the hill near the Central Mosque of Chittagong University.

Slope: 5%

Altitude: 10m from the ground level.

Spacing: 2mX2m (both the plantation).

Age: 15 years for both and indigenous trees plantation.

Distance: between the following sample plots is 15m.

Average height of Eucalyptus camaldulensis is : 20m

Average diameter of Eucalyptus camaldulensis: 22cm

Average height of indigenous trees (Nim - Azadirachta indica) is : 15m

Average diameter of indigenous trees is: 17cm

Table 8: Name of the plant species found in the sample plots under Eucalyptus

camaldulensis and indigenous trees with their total number and average

height in replication 1.

Species name

Eucalyptus

camaldulensis

Under Indigenous

tree

Local

Name

Scientific Name Family

Total

no

Avg.

ht.(c m) Total

no

Avg

ht.(cm)

Blechnum orientali Div. Pteridophyta 1 60 ** **

Ficus semicordata Moraceae 2 30 8 40

Piper longum Piperaceae 1 40 ** **

Aalgash 25 12 30 55

Achargash Microcos paniculata Tiliaceae 4 50 ** **

Arkila Ixora nigricans Rubiaceae 3 25 11 25

Asamgash Eupatorium odoratum

Compositae 10 15 4 15

Asamlata Mikania cordata Compositae 2 30 ** **

110

Dudlata Hemidesmus indicus Periplocaceae 1 30 2 120

Jharugash Thysaenolena maxima Poaceae ** ** 4 60

Kaispata Dalbergia stipularis Leguminosae 6 20 8 45

Kali lata Thunbergia erecta ** ** 2 150

Khosh-

khoshia lata

Byttneria pillosa Sterculiaceae ** ** 1 80

Kurchi/kuch

vine drozop

Holarrhena

antidysenterica

Apocynaceae ** ** 3 45

Lajjabote Mimosa pudica

Mimusaceae ** ** 1 15

Lantana Lantana camara

3 50 2 50

Maittalata ** ** 1 80

Malastoma

/Indian

Rhododendron

Melastoma

malabathricum

Melastomataceae 1 40 18 55

Meda 2 30 3 40

Pitali Trewia polycarpa Euphorbiaceae ** ** 4 40

Putijam Syzygium cumini Myrtaceae 25 50 4 45

Sample 1 9 20 ** **

Sample 8 ** ** 30 10

Sercuti Phyllanthus spp. Euphorbiaceae 10 50 12 55

Shialkata Randia spicata

Rubiaceae 5 30 ** **

Son Imperata cylindrica

Graminae 9 70 15 30

Tagar Tabernaemontana

divericata

Apocynaceae ** ** 1 95

Toynlata Jasminum spp Oliceea 9 100 9 100

Zongli

jumka/Jumkalata Passiflora foetida Passifloraceae ** ** 1 120

** Indicates that the species is absent to that plot.

Replication 2:

111

Location: Mid slope of the hill near the entrance of the Institute of Forestry and

Environmental Sciences of Chittagong University.

Slope: 23%

Altitude: 10m from the ground level.

Spacing: 2mX2m (both the plantation).

Age: 15 years for both and indigenous trees plantation.

Distance: between the following sample plots is 13m.

Average height of Eucalyptus camaldulensis is : 18m

Average diameter of Eucalyptus camaldulensis: 17cm

Average height of indigenous trees (Chickrassy- Chickrassia tabularis) is: 14m

Average diameter of indigenous trees is: 15.5cm

Table 9: Name of the plant species found in the sample plots under Eucalyptus

camaldulensis and indigenous trees with their total number and average

height in replication 2.

Species name

Under

Eucalyptus

camaldulensis

Under Indigenous

tree

Local Name Scientific Name Family

Total

no

Avg.

ht

(c m)

Total

no

Avg

ht (cm)

Axonospora

cylenga

** ** 2 20

Lygodium

flexuosum

Schiziaceae ** ** 1 64

Mucuna spp Papilionaceae ** ** 1 61

Piper longum Piperaceae 1 45 ** **

Aal gassh 8 20 9 21

Arkila Ixora nigricans Rubiaceae 9 20 8 20

Asamlata Mikania cordata Compositae 4 18 9 70

Dhekilota Pteris biurata Pteridaceae 1 100 3 90

Dumur Ficus hispida Moraceae 1 20 3 19

Durba Cynodon dactylon

Graminae 1 55 15 60

112

Ghuruchea Combritum spp Combretacea 4 30 4 35

Lantana Lantana camara Verbenaceae 4 60 2 75

Maittalata 2 120 ** **

Malastoma /Indian

Rhododendron Melastoma

malabathricum

Melastomataceae 1 60 4 60

Muschanilata Stephania

harnendifolia

Menispermaceae ** ** 3 75

Pitraj Aphanamixis

polystachya

Meliaceae ** ** 1 115

Putijam Syzygium cumini Myrtaceae 2 72 3 72

Sercuti Phyllanthus spp. Euphorbiaceae 3 90 4 75

Shornalata Cuscuta reflexa Cuscutaceae ** ** 200 85

Son Imperata cylindrica

Graminae 2 60 3 60

Vitex Clerodendrum

viscosum

Verbenaceae 4 83 3 100

Zongli

jumka/Jumkalata

Passiflora foetida Passifloraceae 1 160 2 38

** Indicates that the species is absent to that plot.

Replication 3: Location: Near the botanical garden of Chittagong University.

Slope: Plain land.

Spacing: 2mX2m (both the plantation).

Age: 12 years for both and indigenous trees plantation.

Distance: between the following sample plots is 16m.

Average height of Eucalyptus camaldulensis is : 17m

Average diameter of Eucalyptus camaldulensis: 14.5cm

Average height of indigenous trees (Pitraj and Polash) is: 14m

Average diameter of indigenous trees is: 13.5cm

113

Table 10: Name of the plant species found in the sample plots under Eucalyptus

camaldulensis and indigenous trees with their total number and average

height in replication 3.

Species name

Eucalyptus

camaldulensis

Under Indigenous

tree

Local

Name

Scientific Name Family

Total

no

Avg.

ht

(c m)

Total

no

Avg

ht (cm)

Cyperus spp Cyperaceae 3 60 5 61

Hyptis suaveolens Lamiaceae 5 15 4 18

Merremia vitifolia Convolvulaceae ** ** 5 65

Premna esculenta Verbenaceae ** ** 4 50

Algash 6 20 6 23

Asamlata Mikania cordata Compositae 7 65 12 60

Lajjabote Mimosa pudica

Mimusaceae 2 12 4 10

Sample 9 2 25 ** **

Son Imperata cylindrica

Graminae 93 45 90 45

Vitex Clerodendrum viscosum Verbenaceae 3 70 4 70

** Indicates that the species is absent to that plot.

Replication 4: Location: Near the Malnichora tea estate of Sylhet.

Slope: 15%

Spacing: 2mX2m (both the plantation).

Age: 16 years for both and indigenous trees plantation.

Distance: between the following sample plots is 11m.

Average height of Eucalyptus camaldulensis is : 22m

Average diameter of Eucalyptus camaldulensis: 19cm

114

Average height of indigenous trees (Simul -Bombax ceiba and Radhachura- Caesalpinia

pulcherrima) is: 17m

Average diameter of indigenous trees is: 18.5cm

Table 11: Name of the plant species found in the sample plots under Eucalyptus

camaldulensis and indigenous trees with their total number and average

height in replication 4.

Species name

Under

Eucalyptus

camaldulensis

Under Indigenous

tree

Local Name Scientific Name Family

Total

no

Avg.

ht.(c m) Total

no

Avg

ht (cm)

Ageratum conyzoides Compositae ** ** 8 48

Crassocephalum

crepideoides

Compositae ** ** 6 58

Flemingia strobilifera 3 52 ** **

Thysanolaena

maxima

Graminae 12 63 ** **

Wikestoemia spp Wikestomiaceae ** ** 1 60

Achargash Microcos paniculata Tiliaceae 1 62 2 60

Arkila Ixora nigricans Rubiaceae 1 50 2 42

Asamgash Eupatorium odoratum Compositae 8 115 10 140

Asamlata Mikania cordata Compositae 2 200 6 165

Chotrapata/

Bichuti Tragia involucrata

Euphorbiaceae ** ** 3 63

Dudlata Hemidesmus indicus

Periplocaceae 1 45 1 60

Ghuruchea Combritum spp Combretacea 15 58 20 50

Huijjagash ** ** 1 80

Muschanilata Stephania harnendifolia Menispermaceae 3 65 3 95

Sample 10

19 86

Shornalata Cuscuta reflexa Cuscutaceae 190 73 200 75

Soilata Pueraria spp Papilionaceae 2 85 2 90

115

Son Imperata cylindrica

Graminae 140 130 200 130

Vitex Clerodendrum viscosum Verbenaceae 10 62 12 60

** Indicates that the species is absent to that plot.

Table 12: Tabulation of total number of plants (herbs, shrubs and tree

seedlings) found in all sample plots of Sylhet and Chittagong

under indigenous trees and Eucalyptus camaldulensis.

Species name

Under

Eucalyptus

camaldulensis

Under

Indigenous trees

Local

Name

Scientific Name Family

Total

no

Avg.

ht.(cm) Total

no

Avg.

ht.(cm)

Ageratum conyzoides Compositae ** ** 8 48

Axonospora cylenga ** ** 2 20

Blechnum orientali Div.Pteridophyta 1 60 ** **

Crassocephalum

crepideoides

Compositae ** ** 6 58

Cyperus spp Cyperaceae 3 60 5 61

Ficus semicordata Moraceae 2 30 7 40

Flemingia strobilifera 3 52 ** **

Hyptis suaveolens Lamiaceae 5 15 4 18

Lygodium flexuosum Schiziaceae ** ** 1 64

Lygodium flexuosum Schiziaceae ** ** 1 64

Merremia vitifolia Convolvulaceae ** ** 5 65

Mucuna spp Papilionaceae ** ** 1 61

Piper longum Piperaceae 2 43 ** **

Premna esculenta Verbenaceae ** ** 4 50

Thysanolaena maxima Graminae 12 63 ** **

Wikestoemia spp Wikestomiaceae ** ** 1 60

Aalgash 39 17. 33 45 33

Achargash Microcos paniculata Tiliaceae 5 56 2 60

Arkila Ixora nigricans Rubiaceae 13 31. 67 21 29

116

Asamgash Eupatorium odoratum

Compositae 18 65 14 77.5

Asamlata Mikania cordata Compositae 20 78. 75 27 98. 33

Chotrapata/

Bichuti Flaria interapta Articaceae ** ** 3 63

Dhekilota Pteris biurata Pteridaceae 1 100 3 90

Dudlata Hemidesmus indicus Periplocaceae 2 37.5 3 90

Dumur Ficus hispida Moraceae 1 20 3 19

Durba Cynodon dactylon

Graminae 1 55 15 60

Ghuruchea Combritum spp Combretacea 19 44 24 42. 50

Jharugash Thysaenolena maxima Poaceae ** ** 4 60

Kaispata Dalbergia stipularis Leguminosae 6 20 8 45

Kurchi/kuch

vine drozop

Holarrhena

antidysenterica

Apocynaceae ** ** 3 45

Lajjabote Mimosa pudica

2 12 5 12.5

Lantana Lantana camara Verbenaceae 7 52 4 62.5

Maittalata 2 120 1 80

Malastoma /Indian

Rhododendron

Melastoma

malabathricum

Melastomataceae 2 50 22 57.5

Meda 2 30 3 40

Muschanilata Stephania harnendifolia Menispermaceae 3 65 6 85

Pitraj Aphanamixis

polystachya

Meliaceae ** ** 1 115

Putijam Syzygium cumini Myrtaceae 27 61 7 58.5

Sample 1 9 20 ** **

Sample 10 ** ** 19 86

Sample 8 30 10 ** **

Sample 9 2 25 ** **

Sercuti Phyllanthus spp. Euphorbiaceae 13 70 16 65

Shialkata Randia spicata

Rubiaceae 7 57.

50

** **

117

Shornalata Cuscuta reflexa Cuscutaceae 190 73 400 80

Soilata Pueraria spp Papilionaceae ** ** 2 90

Son Imperata cylindrica

Graminae 244 76.

25

305 78. 33

Tagar Tabernaemontana

divericata

Apocynaceae

Toynlata Jasminum spp Oliceea 9 100 2 40

Vitex Clerodendrum viscosum Verbenaceae 17 71. 67 19 76. 67

Zongli

jumka/Jumkalata Passiflora foetida Passifloraceae 1 100 1 120

** Indicates that the species is absent to that plot.

Table 12 shows, in all plots of Sylhet and Chittagong, 42 species of plants was

found under indigenous trees while 35 species of plants was found under Eucalyptus

camaldulensis. 7 more species was found under sample plot of indigenous trees than that

of Eucalyptus. In most of the cases, the average number of plants and their average height

found in sample plots under indigenous trees are higher than that of the plots under

Eucalyptus camaldulensis.

Major 10 species found in sample plots under Eucalyptus camaldulensis in

maximum in terms of their total number are Son (Imperate cylindrica), Shornalata

(Cuscuta reflexa), Aalgash, Sample 8, Putijam (Syzygium cumini), Asamlata (Mikania

cordata), Ghuruchea (Combritum spp), Asamgash (Eupatorium odoratum), Vitex

(Clerodendrum viscosum) and Arkilea (Ixora nigricans).

Major10 species found in sample plots under indigenous trees in maximum in terms

of total numbers are Shornalata (Cuscuta reflexa), Son (Imperate cylindrical), Aalgash,

Asamlata (Mikania cordata), Ghuruchea (Combritum spp), Melastome (Melastome

malabathricum), Arkile (Ixora nigricans), Sample 10, Vitex (Clerodendrum viscosum)

and Sercuti (Phyllanthus spp).

Major 10 species found under Eucalyptus camaldulensis in terms of their maximum

height are Asamlata (Mikania cordata), Vitex (Clerodendrum viscosum), Miattalata,

Shialkata (Randia spicata), Son (Imperate cylindrica), Dhekilota (Pteris biurata),

Toynlata (Jasminum spp), Jumkalata (Passiflora foetida), Arkile (Ixora nigricans) and

Shornalata (Cuscuta reflexa).

118

Major 10 species found under indigenous trees interms of their maximum height are

Jumkalata (Passiflora foetida), Putijam (Syzygium cumini), Asamlata (Mikania cordata),

Soilata (Pueraria spp), Sample 10, Muschanilata (Stephania harnendifolia), Maittalata,

Duslata (Hemidesmus indicus), Asamgash (Eupatorium odoratum), and Vitex

(Clerodendrum visecosum).

Comparison can be made in terms of the undergrowth species total number and

average height found under indigenous tree with that of Eucalyptus camaldulensis which

are present in sample plots under both indigenous trees and Eucalyptus camaldulensis.

The topmost 5 species are Shornalata (Cuscuta reflexa), Son (Imperate cylindrica),

Aalgash, Asamlata (Mikania cordata), and Ghuruchea (Combritum spp) (Table 12).

The total number and average height of Shornalata (Cuscuta reflexa) under

indigenous trees are 400 and 80 cm respectively while the figures under Eucalyptus

camaldulensis are 73 and 190 cm respectively.

The total number and average height of Son (Imperate cylindrica)under indigenous

trees are 305 and 78.33 cm respectively while the figures under Eucalyptus camaldulensis

are 244 and 76.25 cm respectively.

The total number and average height of Aalgash under indigenous trees are 45 and

33 cm respectively while the figures under Eucalyptus camaldulensis are 39 and 17.33 cm

respectively.

The total number and average height of Asamlata (Mikania cordata) under

indigenous trees are 27 and 98.33 cm respectively while the figures under Eucalyptus

camaldulensis are 20 and 178.75 cm respectively.

The total number and average height of Ghuruchea (Combritum spp) under

indigenous trees are 24 and 42.50 cm respectively while the figures under Eucalyptus

camaldulensis are 19 and 44 cm respectively.

Of these 5 species when compared the their respective figures of total number and

average height found under indigenous trees with that under Eucalyptus camaldulensis, 4

species, Shornalata (Cuscuta reflexa), Son (Imperate cylindrica), Aalgash, and Asamlata

(Mikania cordata) showed better performance under indigenous trees. Their total number

and average height under indigenous trees are higher than that of Eucalyptus

camaldulensis. 1 species, Ghuruchea (Combritum spp) was found less in number but

higher in average height under indigenous trees than Eucalyptus camaldulensis.

119

4 ground vegetation species out of 5, i.e. 80% of the undergrowth vegetation showed

better performance in plantations of indigenous trees than Eucalyptus camaldulensis

When compared this way, it is observed, for most of the common species (found in

plots of both under indigenous trees and Eucalyptus camaldulensis) their total number and

average height (Table 12) are higher under indigenous trees than that under Eucalyptus

camaldulensis.

Fig: Eucalyptus camaldulensis.

120

8.1.2.1. Is Eucalyptus camaldulensis invasive in Bangladesh?

The result testifies that Eucalyptus camaldulensis affects the indigenous plant

biodiversity under it by reducing the number and growth. There is less vegetation found

under Eucalyptus camaldulensis plantation in comparison to the open areas or under

indigenous trees. In most of cases, soil under Eucalyptus camaldulensis was found totally

or partially exposed and presence of rills and splash soil erosion that enhance top soil

removal or site degradation, of courseEucalyptus camaldulensis can grow on degraded

land and during the field visit, this was proved.

Whether Eucalyptus camaldulensis should be called invasive in Bangladesh or not is

also a controversial issue! Eucalyptus plantation consists of a substantial land area in

Bangladesh (FAO, 1995) although the species is now banned in Bangladesh. The species

was found throughout the country. It is popular in social forestry, agroforestry, home

garden, marginal land plantations and cropland agroforestry programmes. In roadside and

outer periphery of home gardens the species is found commonly in Bangladesh. But this

species is strongly blamed for negative impact on agrs-ecosystem.

Dabral et al. (1987) found less undergrowth vegetation under Eucalyptus plantation

in comparison to that of native condition. Lisa and Michelsen (1993) reported lesser extent

of vegetation under Eucalyptus monoculture than original native trees. Ranasinghe and

Jaysuriya (1991) reported reduced plant diversity and slightly acidic condition under

Eucalyptus than other indigenous trees. Uddin and Mohammad (2003) determined the

impact of Eucalyptus spp on indigenous vegetation and found per hectare considerably

reduced density of undergrowth plant species in comparison to natural forest in

Bangladesh. The present findings are concomitant to those findings. So Eucalyptus

camaldulensis may be termed as an invasive species in Bangladesh!

121

8.1.3. Sample plots in Melaleuca leucodendron and indigenous

trees plantations.

Replication 1:

Location: At the bank of the lake of the Institute of forestry and Environmental Sciences,

Chittagong University.

Site condition:Lower hill slope on the bank of the lake.

Slope: 30%

Spacing: 2mX2m (both the plantation).

Age: 11 years for both Melaleuca leucodendron and indigenous trees plantation.

Distance: between the following sample plots is 7m.

Average height of Melaleuca leucodendron is: 13m

Average diameter of Melaleuca leucodendron: 15cm

Average height of indigenous trees (Kadam -Anthocephallus chinensis and other species)

is : 0m

Average diameter of indigenous trees is: 12.5cm

Table 13:Name of the plant species found in the sample plots under Melaleuca

leucodendron and indigenous trees with their total number and average

height in replication 1.

Species name Under

Melaleuca

leucodendron

Under

Indigenous tree

Local Name Scientific Name Family

Total

no

Avg.

ht.(c m) Total

no

Avg.

ht (cm)

Achargash Microcos paniculata Tiliaceae 4 95 3 100

Apang Nelsonia spp Acanthaceae ** ** 1 40

Arshogonda Withania somnifera 1 90 ** **

Asamlata Mikania cordata Compositae 4 120 10 90

Ghuruchea Combritum spp Combretacea 3 85 3 90

122

Ghuruchea Combritum spp Combretacea 2 60 5 45

Jharugash Thysaenolena maxima Poaceae 5 90 4 93

Koloi lata Coccinea cordifolia Cucurbitaceae 1 98 ** **

Lantana Lantana camara Verbenaceae 1 65 2 62

Maittalata ** ** 1 125

Putijam Syzygium cumini Myrtaceae 3 88 2 92

Sercuti Phyllanthus spp. Euphorbiaceae 1 80 2 86

Shialkata Randia spicata

Rubiaceae 3 115 5 95

Tagar Tabernaemontana

divericata

Apocynaceae ** ** 1 95

Vitex Clerodendrum viscosum Verbenaceae 3 55 3 75

** Indicates that the species is absent to that plot.

Replication 2:

Location: At the back of the Academic Building of the Institute of forestry and

Environmental Sciences, Chittagong University.

Slope: 0 % (Plain land)

Spacing: 2mX2m (both the plantation).

Age: 13 years for both Melaleuca leucodendron and indigenous trees plantation.

Distance: between the following sample plots is 100m.

Average height of Melaleuca leucodendron is: 11m

Average diameter of Melaleuca leucodendron: 14cm

Average height of indigenous trees (Mahagoni, Telsur, Gargan) is: 12m

Average diameter of indigenous trees is: 10.5cm

Table 14: Name of the plant species found in the sample plots under Melaleuca

leucodendron and indigenous trees with their total number and average

height in replication 2.

123

Species name

Under

Melaleuca

leucodendron

Under

Indigenous tree

Local Name Scientific Name Family

Total

no

Avg.

ht.(c m) Total

no

Avg.

ht (cm)

Ageratum conyzoides Compositae 3 30 3 53

Caperis spp Caperidaceae ** ** 4 30

Asamgash Eupatorium odoratum Compositae 4 90 5 85

Asamlata Mikania cordata Compositae 12 63 10 60

Bangla kachu Colocasia esculanta Araceae 7 30 2 50

Dhekilota Pteris biurata Pteridaceae 60 44 72 40

Dumur Ficus hispida Moraceae 1 120 ** **

Lajjabote Mimosa pudica

Mimusaceae 2 20 3 23

Malastoma /Indian

Rhododendron

Melastoma

malabathricum

Melastomataceae 1 65 2 75

Meda ** ** 1 100

Pipul Piper sylvaticum Piperaceae ** ** 1 55

Putijam Syzygium cumini Myrtaceae 1 12 2 10

Sample 11 14 35 ** **

Sample 12 1 120

Sheora Streblus asper Moraceae 1 25 1 27

Son Imperata cylindrica

Graminae 15 60 30 58

** Indicates that the species is absent to that plot.

Replication:3

Location: Near the Pritilata Hall of Chittagong University.

Slope: 0 % (Plain land)

Spacing: 2mX2m (both the plantation).

Age: 15 years for both Melaleuca leucodendron and indigenous trees plantation.

124

Distance: between the following sample plots is 15m.

Average height of Melaleuca leucodendron is: 13m

Average diameter of Melaleuca leucodendron: 14cm

Average height of indigenous trees ( Mix plantation of Krishnochura -Delonix regiaand,

Gutgutia -Bursera serrata and Polash) is : 16m

Average diameter of indigenous trees is: 14.5cm

Table 15: Name of the plant species found in the sample plots under Melaleuca

leucodendron and indigenous trees with their total number and average

height in replication 3.

Species name Under

Melaleuca

leucodendron

Under

Indigenous tree

Local Name Scientific Name Family

Total

no

Avg.

ht.(c m) Total

no

Avg.

ht (cm)

Adiantum lessata ** ** 1 30

Trichosanthes spp Cucurbitaceae 1 60 ** **

Achargash Microcos paniculata Tiliaceae 2 55 5 60

Bet/ Betgota Calamus viminalis Palmeae 4 300 5 280

Dumur Ficus hispida Moraceae 2 25 2 30

Ghuruchea Combritum spp Combretacea 5 85 5 90

Gondo

badali

Paederia foetida 1 100 ** **

Horina

/Horinna Gota

Vitex peduncularis Verbenaceae 14 70 12 88

Kaowatoni Glycosmis spp. Rutaceae 1 70 ** **

Lantana Lantana camara Verbenaceae 1 65 2 50

Melastoma

/Indian

Rhododendron

Melastoma

malabathricum

Melastomataceae 2 70 3 75

125

Son Imperata cylindrica

Graminae 8 70 15 72

** Indicates that the species is absent to that plot.

Replication: 4

Location: Khadim nagar, Sylhet.

Slope: 15 % (Plain land)

Spacing: Irrigular (both the plantation).

Age: 11 years for both Melaleuca leucodendron and indigenous trees plantation.

Distance: between the following sample plots is 18m.

Average height of Melaleuca leucodendron is: 11m

Average diameter of Melaleuca leucodendron: 14.5cm

Average height of indigenous trees (Jam -Syzygium cumini and Kanthal- Artocarpus

heterophyllus) is : 10m

Average diameter of indigenous trees is: 22.5cm

Table 16: Name of the plant species found in the sample plots under Melaleuca

leucodendron and indigenous trees with their total number and average

height in replication 4.

Species name Under

Melaleuca

leucodendron

Under

Indigenous tree

Local Name Scientific Name Family

Total

no

Avg.

ht (c m) Total

no

Avg

ht (cm)

Boewia spp.

** ** 1 25

Dryopteris spp

1 60 ** **

Glycosmis spp Rutaceae 2 55 2 64

Gymnema

acuminatae

Asclepediaceae ** ** 3 45

Leucas aspera Labiatae ** ** 1 35

Lygodium flexuosum Schiziaceae 1 55 ** **

126

Bishkatali Polygonum hydropiper 3 65 2 70

Mal lota Derris scandens 1 90 1 100

Sample 13 12 60 10 63

Sample 14 ** ** 60 15

Shialkata Randia spicata

Rubiaceae 1 120 1 130

** Indicates that the species is absent to that plot.

Table 17: Tabulation of total number of plants (herbs, shrubs and tree

seedlings) found in all sample plots of Sylhet and Chittagong

under indigenous trees and Melaleuca leucodendron

Species name

Under Melaleuca

leucodendron

Under

Indigenous trees

Local

Name

Scientific Name Family

Total

no

Avg.

ht.(cm) Total

no

Avg

ht (cm)

Dhekilota Pteris biurata Pteridaceae 60 44 72 50

Ageratum conyzoides Compositae 3 30 3 53

Caperis spp Caperidaceae ** ** 4 30

Adiantum lessata ** ** 1 30

Trichosanthes spp Cucurbitaceae 1 60 ** **

Boewia spp

** ** 1 25

Dryopteris spp

1 60 ** **

Glycosmis spp Rutaceae 2 55 2 64

Gymnema

acuminatae

Asclepediaceae ** ** 3 45

Leucas aspera Labiatae ** ** 1 35

Lygodium flexuosum Schiziaceae 1 55 ** **

Panicum spp Graminae ** ** 60 15

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Asamlata Mikania cordata Compositae 16 91 20 75

Son Imperata cylindrica

Graminae 8 70 15 72

Ghuruchea Combritum spp Combretacea 10 115 8 75

Horina

/Horinna Gota

Vitex peduncularis Verbenaceae 14 70 12 56

S-13 12 60 10 63

Achargash Microcos paniculata Tiliaceae 6 75 8 80

Shialkata Randia spicata

Rubiaceae 4 117.5 6 112.5

Asamgash Eupatorium

odoratum

Compositae 4 90 5 85

Bet/ Betgota Calamus viminalis Palmeae 4 300 5 280

Malastoma /Indian

Rhododendron

Melastoma

malabathricum

Melastomataceae 3 67.5 5 75

Jharugash Thysaenolena maxima Poaceae 5 90 4 93

Putijam Syzygium cumini Myrtaceae 4 50 4 51

Lajjabote Mimosa pudica

Mimusaceae 2 20 3 23

Vitex Clerodendrum viscosum Verbenaceae 3 55 3 75

Bangla kachu Colocasia esculanta Araceae 7 30 2 50

Bishkatali Polygonum lanatum Polygonaceae 3 65 2 70

Lantana Lantana camara Verbenaceae 1 65 2 62

Sercuti Phyllanthus spp. Euphorbiaceae 1 80 2 86

Apang Nelsonia spp Acanthaceae ** ** 1 40

Maittalata ** ** 1 125

Mal lota Derris scandens 1 90 1 100

Meda ** ** 1 100

Pipul Piper sylvaticum Piperaceae ** ** 1 55

Sample 12 ** ** 1 120

Tagar Tabernaemontana

divericata

Apocynaceae ** ** 1 95

Arshogonda Withania somnifera 1 90 ** **

128

Dumur Ficus hispida Moraceae 3 72.5 ** **

Gondobadali Paederia foetida Rubiaceae 1 100 ** *

Kaowatoni Glycosmis spp. Rutaceae 1 70 ** **

Koloi lata Coccinea cordifolia Cucurbitaceae 1 98 ** **

Sample 11 14 35 ** **

Table 17 shows that, 31 plant species was found in all sample plants of under

Melaleuca leucodendron tree and 34 plant species was found under indigenous trees. Only

3 undergrowth plant species was found more under indigenous trees than Melaleuca

leucodendron.

Major 10 species found under Melaleuca in terms of their total number are Dhekilata

(Pteris biurata), Asamlata (Mikania cordata), Sample 11, Horina (Vitex peduncularis),

Sample 13, Ghuruchea (Combritum spp), Son (Imperate cylindrical), Bangla Kachu

(Colocasia esculanta), Achargash (Microcos paniculata) and Jharugash (Thysaenolena

maxima).

Major10 species found under indigenous tree in terms of their total number are

Dhekilata (Pteris biurata), Panicum spp, Asamlata (Mikania cordata), Son (Imperate

cylindrical), Ghuruchea (Combritum spp), Horina (Vitex peduncularis), Sample 13,

Achargash (Microcos paniculata), Shialkata (Randia spicata) and Asamlata (Mikania

cordata). 5 major species (in terms of their total number under indigenous trees) that were

present in common in sample plots both under indigenous and Melaleuca leucodendron

trees and their total number and average height found in plantations of indigunous and

Melaleuca leucodendron trees can be considered for rapid comparison of invasiveness of

Melaleuca leucodendron.

5 species are Dhekilata (Pteris biurata), Asamlata (Mikania cordata), Son (Imperate

cylindrica), Ghuruchea (Combritum spp), and Horina (Vitex peduncularis).

Total number and average height of Dhekilata (Pteris biurata) under Melaleuca

leucodendron are 60 and 44 cm respectively while the figures under indigenous trees are

72 and 50 cm respectively.

Total number and average height of Asamlata (Mikania cordata) under Melaleuca

leucodendron are 16 and 91 cm respectively while the figures under indigenous trees are

20 and 75 cm respectively.

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Total number and average height of Son (Imperate cylindrica) under Melaleuca

leucodendron are 8 and 70 cm respectively while the figures under indigenous trees are 15

and 72 cm respectively.

Total number and average height of Ghuruchea (Combritum spp) under Melaleuca

leucodendron are 10 and 115 cm respectively while the figures under indigenous trees are

8 and 75 cm respectively.

Total number and average height of Horina (Vitex peduncularis) under Melaleuca

leucodendron are 14 and 70 cm respectively while the figures under indigenous trees are

12 and 56 cm respectively.

Out of 5 species, 2 species Dhekilata (Pteris biurata) and Asamlata (Mikania

cordata) were found having average height and total number greater than under

indigenous trees respective figures under Melaleuca leucodendron. Other 2 species

Ghuruchea (Combritum spp) and Horina (Vitex peduncularis) were found having total

number and average height under Melaleuca leucodendron than that under indigenous

trees. 1 species Asamlata (Mikania cordata) out of these 5 undergrowth vegetation was

found having greater in number but average height was less under indigenous trees

plantation in comparison to Melaleuca leucodendron plantation. On the other hand

average height of Asamlata (Mikania cordata) was higher but total number was less under

Melaleuca leucodendron plantation than under indigenous trees plantation.

So inference can be drawn that of all the undergrowth vegetation found in the plots

under plantation of indigenous trees and Melaleuca leucodendron, 50% of the

undergrowth species was found showing well growth under Melaleuca leucodendron and

50% of the vegetation grows well under indigenous trees.

8.1.3.1. Is Melaleuca leucodendron invasive in Bangladesh?

The result shows apparently that Melaleuca does not have significant impact on

undergrowth vegetation in comparison to native trees. But Melaleuca is blamed in many

countries to impose negative impact on biodiversity of native flora and fauna (Serbesoff

King, 2003). Pernas and Francois (2003) ascertained that Melaleuca rapidly invades

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disturbed and undisturbed habitats and forms dense impenetrable forest and ultimately

displace native plants. But present findings confront with those findings.

Actually, there is no established plantation of Melaleuca in our country and no

Melaleuca large area monoculture is raised. As an ornamental plant, many institutions

have planted dispersely Melaleuca on limited scale for beautification of the Premise.

Probably, that’s why Melaleuca could not produce effect on the ecosystem yet. But these

species is strongly objected for producing health hazard (Pollen allergy) because the

flowers and new folige produce airborn substance that causes severe asthma- like

symptom in Sensitive people.

Fig : Melaleuca

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8.1.4. Comparison of invisibility of Acicia auriculiformis,

Eucalyptus camaldulensis and Melaleuca leucadendron:

From field visit, it was seen less extent of vegetation under both Acacia

auriculiformis and Eucalyptus camaldulensis. My experiment findings also testify this.

But under Melaleuca no sensible difference was observed in comparison the open nearby

open area or nearby indigenous tree undergrowth.

In all sample plots of Sylhet and Chittagong all together 52 undergrowth plant

species was found under indigenous trees and 30 undergrowth plant species was found

under Acacia auriculiformis. 22 more undergrowth plant species were found under

indigenous trees, which were absent under Acacia auriculiformis. In most of the cases the

average number of plants and their average height in sample plots of indegenous trees are

higher than that of plots under Acacia auriculiformis.

In all sample plots of Sylhet and Chittagong, all together 42 species of undergrowth

plants was found under indigenous trees while 35 species of undergrowth plants was found

under Eucalyptus camaldulensis. 7 more species was found under sample plot of

indigenous trees than that of Eucalyptus. The average number of plants and their average

height In most of the cases, found in sample plots under indigenous trees are higher than

that of the plots under Eucalyptus camaldulensis.

Al together 31 undergrowth plant species was found in all sample plots under

Melaleuca tree and 34 undergrowth plant species was found under indigenous trees. Only

3 undergrowth plant species was found more under indigenous trees than Melaleuca

leucadendron.

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Result shows 40% of the undergrowth vegetation was seen growing better under

Acacia auriculiformis, 20% of the undergrowth vegetation under Eucalyptus

camaldulensis and 50% of the undergrowth vegetation under Melaleuca leucodendron

plantation. If invasiblity of these three species is ranked, Eucalyptus camaldulensis ranks

first followed by Acicia auriculiformis and Melaleuca leucadendron.

8.1.5. Mikania cordata, Eupatorium odoratum, Ipomea carnea

and Lantana camara –invasive species in different ecosystems of

Bangladesh:

8.1.5.1 Asamlata (Mikania cordata).

Family: Asteraceae

Vegetative character: Mikania cordata is perennial fast growing weed. Mikania

cordata is a vine.The leaves of Mikania are cordate shaped. Mikania cordata shows

vigorous branching behaviour. On average 25-30 branches were found on sites of medium

infestation in 2m by 2m random sample plots. Most of the branches develop sub-branch

from their nodes except some base nodes. From nearly 50% of the nodes of horizontal soil

touching branches develop sub-branches. From each aerial branches node, 2 leaves and

one branch develop. The branch comes out from the middle of the leaf base. Sub-branches

again develop sub-branches from their nodes. This level continues and ultimately a

Mikania bush is formed and suppress the indigenous plant to grow. The nodel length of

the branches averages 10-12 cm. It was found that a thicket of 2.5 m tall Mikania had

developed 30 branches. The branches of some node are long (80-100 cm) and that of

others are small (10 cm). The upper side of the aerial horizontal branches is blackish blue

while the lower root is green. Stem with white hair while the leaves are smooth.

Sometimes branches (vines) coalesces together themselves spirally to form a bunch of the

tops and all the tops joint by then spiral up when they get any support. If the support is a

free or seedling they even reach to the top and suppresses the plant.

133

Habitat: Generally Mikania cordata prefers sunny, moist and fertile places, such

as road sides and the sides of stream. However it was also found it in arid soil and shady

places. It cannot tolerate dense shade. Observation suggests that it can grow in fertile or

unfertile soil. The various habitat attributes to extensive invasibility. It is currently

distributed in the whole country as a massive problem weed. The probable causes for the

high infestation of Mikania in Bangladesh is the high disturbance to the ecosystems and

the absence of host-specific natural enemies.

Growth: Growth of Mikania cordata is 2.2 m per month.

Biomass: In randomly taken sample plots of 2m by 2m, the weight of Mikania

cordata was found to be 2.50 kg to 4.20 kg on sites of medium infestation to heavy

infestation respectively. When converted to hectare, the biomass is 6250kg/ha to

10500kg/ha on sites of medium infestation to heavy infestation respectively.

Mode of reproduction: Multiplication of the weed is through wind-dispersed seeds

and vegetative means. Mikania reproduces vigorously by seeds. Mikania also reproduces

by vegetative means.

Ecological threat: Survey showed that it poses a serious threat to natural forests,

plantations and agricultural systems in Bangladesh. The weed can smother and pull over

plants, and the damage caused is extensive. Mikania cordata is a destructive weed of the

natural and man made forests in Bangladesh. Mikania quickly climbs over trees and

shrubs and even kill them by strangling and shading. Some of the Mikania vines coalesces

together at the top of the branches and ascends up when they get any support. Tree

seedlings are used as support by the Mikania and reaches even at the top of the seedlings

or saplings and sometimes cover them completely and suppress them to grow. Most of the

cases, they are difficult to remove completely because of massive growth. Sometimes the

weed completely covers the indigenous vegetations that grows with it and suppresses other

native plants to grow in that area. The weed competes with other indigenous plants for

nutrients and moisture.

Economic threat: Cost-escalation and income reduction are the main economic

impacts due to Mikania infestation in cultivated lands. Forests need frequent weeding to

get rid of the weed.

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Table 18: Showing some of the allied species growing with Mikania cordata

Local Name

Scientific Name Family

Adiantum lessata

Ageratum conyzoides Compositae

Crassocephalum

crepideoides

Compositae

Crotalaria pallida Papilionaceae

Cyperus spp Cyperaceae

Dalbergia stipularis Leguminosae

Dryopteris spp

Hyptis suaveolens Lamiaceae

Leucas aspera Labiatae

Ludwigia repens Onagraceae

Merremia vitifolia Convolvulaceae

Mucuna spp Papilionaceae

Nelsonia spp Acanthaceae

Passiflora foetida Passifloraceae

Premna esculenta Verbenaceae

Thysanolaena maxima Graminae

Algash

Alulata Dioscorea alata

Discoriaceae

Asamgash Eupatorium odoratum Compositae

Bash ghass Graminae

Bet/ Betgota Calamus viminalis Palmeae

Bon-alulata Diascorea spp Diascoreaceae

Chailata/Shimlata Pueraria spp

Papilianaceae

Dudlata Hemidesmus indicus

Periplocaceae

Gondobadali Paederia foetida Rubiaceae

135

Kali kochi shak Vigna spp. Leguminosae

Khosh khoshia lata Byttneria pillosa Sterculiaceae

Koloi lata Coccinea cordifolia Cucurbitaceae

Lantana Lantana camara Verbenaceae

Muschanilata Stephania harnendifolia Menispermaceae

Sample 15

Son Imperata cylindraca Verbenaceae

Sample 16

Sample 17

Fig : Mikania

136

i

8.1.5.2 Asam gash (Eupatorium odoratum)

Family: Asteraceae

Introduction: Eupatorium odoratum is a dominant, competitive and wide

spread invasive species in Bangladesh. In Bangladesh it is a common invasive weed of

fallows and bush fallow sites, wastelands and forests.

Vegetation characters: The species is soft when young and hard when old. Leaves

are triangular, hairy and rough with three prominent veins. Eupatorium is a perennial

shrub, which attains a height of 3m. But, in maximum cases the height remains within

2.5m. Eupatorium sometimes adopt a climbing habit and is seen to reach a height of 5.5m.

Eupatorium grows in bunch. From the base of each older stem several (4-5)

branches come out. From the nodes of each individual stem, branches again come out.

This process continues and ultimately a bush of Eupatorium is formed. A Eupatorium

stem of 1.5 m height gives rise to nearly 5 / 6 branch stems on an average. The average

nodal length of an older stem may be 15-18 cm.

No of stem per unit area: In 2m by 2m sample plot taken randomly, it was found

on an average, 70 stems in sites heavily infested by Eupatorium and 50 stems in sites of

medium infestation.

Biomass: In 2m by 2m sample plot, taken randomly from the thicket of

Eupatorium odoratum, the biomass ranges from 4.10 kg to 6.30 kg (of height range 0.80 to

1.6 m respectively) depending on the intensity of invasion to the habitat. When converted

137

to hectare, the biomass is10250 kg per ha to 15750 kg per ha on sites of medium

infestation to heavy infestation respectively.

Growth: Growth of Eupatorium odoratum is 45cm per month in growing season

(March-July).

Mode of reproduction: It can reproduce both by seeds and vegetative means.

Eupatorium is a prolific seed producer. The seeds were seen to disperse to a wider range,

which is a good character of an invasive plant. During the dry season, the weeds including

the root system dry up, but after the rains they resprout rapidly within few days. Even

burnt weeds may re-grow fast through the stem base.

Habitat: Eupatorium grows well in open areas. Of course, Eupatorium has thin

affinity to habitat near the wetland, canal side, pond embankment etc, in comparison to

other invasives like Mikania cordata, Lantana camara, Melaleuca leucodendron etc.

Ecological threat: The species was seen to causes large-scale habitat destruction

by suppressing the other vegetation and can be identified as a threat to biodiversity. The

plant is extremely well distributed by seed and grows into dense impenetrable bushes out

competing all indigenous vegetation and animal access to food and water sources.

Eupatorium has the ability to establish itself very rapidly and to suppress persistent plants

or nearby plants by its massive growth. Its rapid multiplication and the resprouting ability

of established plants make it very difficult to control infestations.

With the increase of age of the bush of Eupatorium, the leaves in the lower part of

the plant dies out giving a skeletal appearance to the lower part but the upper portion of

the bush or plant remain vigorous and lush green. Below the older part of the bush, no

undergrowth can be seen and the soil is totally exposed. Rotten leaves and stems of the

plant is seen there. The bush looks green at the first appearance, but anybody opens the

bush by cutting down some stems from one side, one can see the beggar description

condition of the lower bush part. The bush also dense enough to obstruct the movement of

animals (vertebrate/ invertebrate) through it. There is almost no undergrowth vegetation is

seen in the core part of the bush. Lesser amount of vegetation was seen to grow below the

outer circumference of the bush. It is a common weed in waste lands and agricultural lands

in Bangladesh.

Table 19: Some of the allied species growing with Eupatorium odoratum.

138

Local Name

Scientific Name Family

Ageratum conyzoides Compositae

Borreria articularis Rubiaceae

Bridelia stipularis Euphorbiaceae

Commelina spp. Commelinaceae

Crassocephalum

crepideoides

Compositae

Crotalaria pallida

Papilionaceae

Dalbergia stipularis Leguminosae

Dryopteris spp

Glycosmis spp Rutaceae

Hedyotis scendans Rubiaceae

Ludwigia repens Onagraceae

Merremia vitifolia Convolvulaceae

Mucuna spp Papilionaceae

Thysanolaena maxima Graminae

Algash

Arkila Ixora nigricans Rubiaceae

Asamlata Mikania cordata Compositae

Bash ghass Graminae

Chotrapata Flaria interapta Articaceae

Croton Croton bonplandianum Euphorbiaceae

Dul kolmi Ipomea carnea Convolvulaceae

Dumur Ficus hispida Moraceae

Ghotkochu Typhonium trilobata Araceae

Ghuruchea Combritum spp Combretacea

Horina /Horinna

Gota

Vitex peduncularis Verbenaceae

Kantabegun Solanum torvum Solanaceae

Lantana Lantana camara Verbenaceae

139

Ludwigia

adscendens L.

Ludwigia adscendens Onagraceae

Malastoma /Indian

Rhododendron

Melastoma malabathricum Melastomataceae

Shornalata Cuscuta reflexa Cuscutaceae

Ulu son Saccharum spontaneum Cramineae

Son Imperata cylindraca Verbenaceae

Vitex Clerodendrum viscosum Verbenaceae

8.1.5.3 Lantana (Lantana camara)

Family: Verbanaceae

Vegetative characteristics: Lantana camara is a bushy spreading, tangled,

multibanched, and thicket-forming perennial shrubt. Stem hairy, cylindrical. A one-year-

old Lantana bush contains 12-20 mature stems when counted at the basal part. Each

individual stem again gives rise to several branch as the height of the bush increases.

Ultimately the whole area near the bush base is covered by Lantana. If the bush/stems gets

support, then they climb higher which may extend up to 5-7m. If they don’t get the

support (e.g. electric post, fence, tree etc.), the bush height remains within 1.5-2.0m and

spreads laterally. Leaves opposite, ovate-deltoid to triangular-oblong, coarsely serratedat

the margin, conspicuously nerved, strongly smelled and hairy. Leaves are non-palatable to

animals. A mature stem is white or brown white, at younger stage it is green. A mature

Lantana stem is hard and turn woody. Yellow, deep yellow and pick coloured bunchy

flowers are seen to bloom in Lantana plant. Sometimes all those three-colour combination

can be found on one flower while they may be found separately on others.

Habitat: It is a common weed of wasteland, agricultural lands roadsides and

borderland of forest in Bangladesh. It is found in all the districts in Bangladesh.

Growth: Growth of Lantana camara is 22cm per month on an average.

Biomass: In 2m by 2m sample plot, taken randomly from the thicket of Lantana

camara, the biomass is on average 7.70 kg. When converted to hectare, the biomass

is19250 kg per ha on sites of heavy infestation.

140

Mode of reproduction: Lantana reproduces mainly by seeds. It also reproduces

vegetatively. Cuttings grow when they are planted in the soil. If a Lantana bush is cut, it

will resprout to original bush within a few days.

Ecological threat: A one year old Lantana bush may cover 2-2.5m radius area

completely and do not allow other plants to grow under the bush. Very few or no herbs or

shrubs are seen to grow through a Lantana bush. Soil remains exposed under a complete

Lantana bush. Spines are found in the Lantana stem. So movement is problematic through

Lantana infested habitat. Animal movement through Lantana bush seems to be very

problematic. This shows clearly that Lantana is a aggressive and invasive plant which

suppresses indigenous plants to grow near or under it.

Table 20: Some of the allied species, which grow over the Lantana bush or near it.

Local Name

Scientific Name Family

Ageratum conyzoides Compositae

Commelina spp. Commelinaceae

Crassocephalum

crepideoides

Compositae

Crotalaria pallida

Papilionaceae

Dalbergia stipularis Leguminosae

Dryopteris spp

Glycosmis spp Rutaceae

Ludwigia repens Onagraceae

Mucuna spp Papilionaceae

Thysanolaena maxima Graminae

Algash

Asamgash Eupatorium odoratum Compositae

Asamlata Mikania cordata Compositae

Bash ghass Graminae

Chotrapata Flaria interapta Articaceae

Croton Croton bonplandianum Euphorbiaceae

Dumur Ficus hispida Moraceae

141

Ghotkochu Typhonium trilobata Araceae

Kali kochi shak Vigna spp. Leguminosae

Khosh khoshia lata Byttneria pillosa Sterculiaceae

Koloi lata Coccinea cordifolia Cucurbitaceae

Malastoma /Indian

Rhododendron

Melastoma malabathricum Melastomataceae

Son Imperata cylindraca Verbenaceae

Ulu son Saccharum spontaneum Cramineae

Fig: Lantana.

142

8.1.5.4. Dul kolmi (Ipomoea carnea).

Family: Convolvulaceae

Vegetative characteristics: Ipomoea carnea is a perinnial shrub with hard stem,

greener at the top portion and gray coloured at the base. Stem is cylinderical. Ipomea

carnea can become 3-4 m tall. Leaves are long cordate shaped with 20-25 rives steming

from the mid rib. White powdery substance present on the older leaves. From main

branch, a few sub-branches come out specially horizontal stems touching the soil. Flowers

are off white, funnel shaped, petals jointed. Flowers come from the stem nodal upper base

of the leaves.

Habitat: It is a Common weed of all habitats In Bangladesh. Can come up in

waterlogged areas. Widely seen in roadside and farm ditches, waterlogged areas,

shorelines, river-sides. In Bangladesh it is seen in almost all districts Ipomoea carnea

grows well in wet areas. Canal sides, creek sides, road sides, railway sides, pond

embankment, river sides etc wet places are most affected by Ipomea. Agricultural and

wastelands whether they are wet or not are also affected by Ipomea.

Growth: Growth of Ipomoea carnea is 43.5cm per month.

Ecological threat: Invasiveness of Ipomoea carnea has been obvious because of

their rapid expansion and widespread detrimental ecological impacts. From the field

survey it was found occurrence of Ipomea as a problematic weed in nearly all moisture

rich habitat. Ipomea was seen affecting badly indigenous biodiversity by suppressing and

displacing the nearby plants by its massive self growth. This is non-palatable to animals.

143

Vegetative growth is too much successful. Ipomea along with other invasives like Mikania

cordata, Eupatorium odoratum, Imperata cylindraca, Eichhornea carassipes invades the

ecosystem badly in Bangladesh. Water channels are sometimes mostly occupied by

Ipomoea and Eichhornea carassipes that obstructs water flow. It is a frequent weed in

waste lands in Bangladesh.

Table 21: Some of the allied species found growing with Ipomoea carnea

Local Name

Scientific Name Family

Adiantum lessata

Ageratum conyzoides Compositae

Axonospora cylenga

Borreria articularis Rubiaceae

Cyperus spp Cyperaceae

Dryopteris spp

Glycosmis spp Rutaceae

Gymnema acuminatae Asclepediaceae

Hyptis suaveolens Lamiaceae

Leucas aspera Labiatae

Ludwigia repens Onagraceae

Mucuna spp Papilionaceae

Pistia strateoties Araceae

Polygonum spp

Premna esculenta Verbenaceae

Thysanolaena maxima Graminae

Asamgash Eupatorium odoratum Compositae

Asamlata Mikania cordata Compositae

Bash ghass Graminae

Bishkatali Polygonum lanatum Polygonaceae

Chotrapata Flaria interapta Articaceae

Croton Croton bonplandianum Euphorbiaceae

Kochuripana Eichhornea crassipes Pontederiaceae

144

Malastoma/Indian

Rhododendron

Melastoma malabathricum Melastomataceae

Son Imperata cylindraca Verbenaceae

Ulu son Saccharum spontaneum Cramineae

Fig : Ipomea

145

8.1.6. Comparison of invasiveness among Mikania cordata,

Eupatorium odoratum, Ipomoea carnea and Lantana Camara:

All these species were found to create massive destruction to forests and agricultural

lands in Bangladesh. The growth of Mikania cordata was 220 cm per month, Eupatorium

odoratum 45 cm per month, Ipomoea carnea 43.5cm per month and Lantana Camara

22cm per month. Mikania cordata and Eupatorium odoratum showed massive growth and

reproduction followed by Ipomoea carnea and Lantana Camara. They all can be

rigorously blammed for suppressing and displacing indigenous vegetation by their massive

growth and reproduction. From practical field investigation and observation, the four

species, on the basis of their level of destruction, Mikania cordata is the worst weed

followed by Eupatorium odoratum, Ipomoea carnea and Lantana Camara.

8.1.7. Limitations of the study

Quantitative evidence for the loss of biodiversity due to invasive plants was

assessed from paired sample plot surveys, where native species abundance,

richness or diversity was compared between areas under indigenous trees and

146

invasive trees. These observations are problematic because differences in

biodiversity between the invaded and uninvaded areas may be related to other

factors beside invasion. For example, the sites may have differed in diversity long

before the alien plants arrived.

In the present studie, species diversity was not surveyed in the sample plot before

and after an invasion. As with the paired plot studies, direct effects of alien plants

on native biodiversity may be overestimated if an external factor, like disturbance,

biotic factors, micro climate, nutrient status, microbial activity etc. may affects the

paired plots differently.

Careful monitoring of study sites over long time is needed to eleminate the

external factors that have had important effects on diversity in the study site, but

these could not be done for shortage of time. That’s why the present data might

have some biasness and therefore, the accuracy of the result might have some

corruptions.

Local names or scientific names of many plants could not be known. That’s why

in some cases they could not be presented to the result. Biasness in data analysis

and inaccuracy in the result might originate from this.

The paired sample plots were not exactly identical in all aspect, because finding

that type of site is difficult unless they are created. They might differ, at least to

some extent in slope, aspect, altitude etc. So undergrowth vegetation in the sample

plots may be affected by other external factors beside biological invasion.

8.1.8. Recommendations

The impacts of alien invasive species may be immense, insidious, and usually

irreversible. They may be as damaging to native species and ecosystems on a

national and global scale as the loss and degradation of habitats. So, policy makers,

biologists, foresters, silviculturists, entomologists, zoologists, botanists, naturalists,

scientists of various research organizations (e.g. Forest Department, Bangladesh

Rice Research Institute, Department of Fisheries, different NGOs working with

environment and biodiversity) and civil society should be aware of biological

147

invasion in Bangladesh and formulate appropriate measures unitedly so as to tackle

the problem of biological invasion or at least, halting it from further deterioration.

We should undertake surveys and research to assess the extent to which indigenous

or native species are already invaded by alien species and assess the economic

implications of these invasions. The findings of such studies need to be much more

widely publicized or broadcast and in particular must be brought to the attention of

government planners and regulators so that actions can be taken to control or

eradicate the alien invasive plants.

National databases about alien invasives should be established . Such databases

should list recognized invasives, give case studies of levels of damage and of

control measures employed.

Raising awareness of the IAS problem and potential solutions through relevant

organizations and frameworks at national level. Creating linkages among

governments and the private sector, and across disciplines; hosting workshops on

strategic planning, priority setting, and the development of new and better tools to

address invasive alien species problem.

Summarizing scientific and technical information of the alien invasive plants to

make it readily available to policy makers, scientists, educators, and other

audiences to formulate steps to be taken against invasive species.

Indigenous species should be given preferences in plantation programs first. If the

native species are not able to provide the required productions, than the exotics

may be considered for plantations only. Extensive studies should also be carried

out by scientist, botanists and foresters on further effect of these species in the

ecosystem.

In case of intentional introduction, judicious manipulation of the matters should be

done regarding the actual necessity of introduction of that plant, the past history of

invasiveness of the plant to the country of its native origin or to other country,

insects and pests associated with the alien plants, if becomes invasive in future

here in Bangladesh, their possible control method should be specified to reduce

future degradation of the environment. If the species show sign of biological

invasion to other countries, they must be discarded to introduce in Bangladesh.

148

Should develop institutional mechanism, to reach decisions on whether proposed

introductions should be authorized, to develop import and release guidelines and to

set specific conditions for alien plants where appropriate.

Give utmost importance to effective evaluation and decision-making processes

during plant introduction. Carry out an environment impact assessment and risk

assessment as part of the evaluation process before coming to a decision on intro-

ducing an alien species.

Where relevant, require that specific experimental trials (e.g. to test infectivity of

alien species) be conducted as part of the assessment process. Such trials are often

required for biological control proposals and appropriate protocols for such trials

should be developed and followed.

Criminal penalties and civil liability for the, consequent eradication or control costs

of unauthorized intentional introductions can be developed.

Quarantine rules should be strictly followed for the plants imported from overseas

by authorized institutions. Quarantine and border control regulations and facilities

should be put in place and train staff to intercept the unintentional introduction of

alien species. Quarantine and border control regulations should not be premised

only on narrow economic grounds that primarily relate to agriculture and human

health, but, in addition, on the unique biosecurity threats each country is exposed

to.

Preventing the introduction of alien invasive species would be the cheapest, most

effective and most preferred option and warrants the highest priority.

Rapid action to prevent the introduction of potential alien invasives is appropriate,

even if there is scientific uncertainty about the long-term outcomes of the potential

alien invasion.

The intentional introduction of an alien species should only be permitted if the

positive effects on the environment outweigh the actual and potential adverse

effects. This principle is particularly important when applied to isolated habitats

and ecosystems, such as islands forests.

The intentional introduction.of an alien species should only be considered if no

native species is considered suitable for the purposes for which the introduction is

being made.

149

Unfortunately, it can be very difficult to control unintentional introductions that

occur through a wide variety of ways and means. Identification and management of

pathways leading to unintentional introductions should be maid. Important

pathways of unintentional introductions include: national and international trade,

tourism, shipping, ballast water, fisheries, agriculture, construction projects,

ground and air transport, forestry, horticulture, landscaping, pet trade and

aquaculture.

Efforts should focus on building a distributed information system by linking

national and international databases and overall information on the issue of

invasive alien plants. Efforts at the notional level should: Reviewing relevant

policies, legislations and institutions to identify conflicts, gaps and inconsistencies;

and strengthen or develop effective national measures for the prevention,

eradication, and control of alien species.

Active public engagement is critical to successful invasive plant management.

State and organizations working with forest and environment should work to

motivate the public successfully regarding the negative impact of invasive alien

plants on environment and coordinate their efforts for greater national benefit,

leading to an informed public that supports actions to reduce the threat of the alien

plants.

Preventing the introduction of alien invasive species should be the first goal. When

prevention has not been successful, steps to mitigate adverse impacts of invasive

plants may include eradication, containment and control. Eradication, containment

and control method for invasives like Eupatorium odoratum, Mikania cordata,

Lantana camara, Eichhornea crassipes, Ipomea carnea Ageratum conyzoides,

Ludwigia adscendens, Imperata cylindrica etc. should be developed through

research. Early detection of new introductions of potential or known alien invasive

species, together with the capacity to take rapid action, is often the key to

successful and cost-effective eradications.

Expert advice should be sought regarding eradication, control, or containment of

invasive plants where appropriate. A multidisciplinary approach might be best, as

recommended in the IUCN Guidelines for invasive species.

150

Control methods should be socially, culturally and ethically acceptable, efficient,

non-polluting, and should not adversely affect native flora and fauna, human health

and well-being, domestic animals, or crops.

Increase the exchange of information between scientists and management agencies,

not only about alien invasive species, but also about control methods.

For Eupatorium odoratum, Mikania cordata, Lantana camara, and Ipomea carnea

spread should be checked to save our forests, agricultural lands and waste lands

from their invasion. All these species are spreading naturally by their massive

reproduction and growth. Control by mechanical means may prove best to check

their spread. It would be feasible to slash and burn the weeds. Regular monitoring

of the infested sites should be done.

Plantation of Acacia auriculiformis and Eucalyptus camaldulensis in Bangladesh

may be planted in limited scale in the degraded sites where performance of local

species is poor. After the site condition has improved much after a certain period,

they should be replaced by native species even though the performances of the

natives are poor. The nominal loss of some amount of timber or fuel wood would

be easily compensated by long-term ecological balance and biodiversity

conservation imparted by the native plants. It can be recalled here that Government

of Bangladesh has already banned planting of Eucalyptus in Bangladesh, but

people are still planting Eucalyptus because of ignorance.

Plantation of Melaleuca leucodendron can be done in limited scale for ornamental

purpose only. Large scale plantation of Melaleuca leucodendron can be discarded

as this tree has already been leveled as invasive tree in different countries of the

world (particularly in Florida, USA) although no marked effect of Melaleuca was

observed from the research result.

151

Conclusion It is acknowledged that invasive species are one of the major threats to biological

diversity worldwide. Invasive alien species are an enormous threat to plant and diversity,

as well as to the economy of many countries and the well being of their people.

Bangladesh is also facing the problem of invasive alien species, which are introduced

deliberately or have spread naturally to our environment. Countering this threat and

saving our valuable native plant and animal biodiversity from their threat is likely to

become a huge challenge for Bangladesh, and the costs would be significant. However,

the costs of ignoring the problem will be almost incalculable - lost agricultural

production, spoiled crops, human disease and allergies, clogged catchments and water

bodies, reduced water availability, threatened rural livelihoods, disrupted ecosystem

services, and species extinctions.

Exotic species are playing a vital role in the plantation forestry of Bangladesh. Due to not-

well-thought-out government policies, weak enforcement of existing safeguards, and lack of

popular awareness, alien invasive species are taking over natural habitats and rapidly changing the

native character of the ecosystem. It is quite unfortunate that the long-term, and even short-term,

adverse effects were not considered while introducing these alien invasive species to Bangladesh.

Apart from providing ecological balance the adverse impacts on native biodiversity can be reduced

if introduction and spread of alien invasive species are stopped.

Combating alien invasive species in Bangladesh will be very difficult because of lack of

awareness and proper initiatives. The selection of species for the introduction in the plantation

must be done very carefully. No species should be introduced without adequately evaluating their

detailed life history, probable impacts and probable benefits in Bangladesh. Any further

introduction of such species must be stopped. People should be made aware of the negative

consequences of introducing alien species and the true values of sustaining and reviving the

indigenous species. Bangladesh is rich enough in biodiversity. We have almost all the major types

of flora and fauna with the characteristics of high growth rate, high economic value, high market

demand, etc. hence, it would be more prudent if the concerned authorities could try to improve and

popularize these indigenous species instead of indiscriminately introducing alien invasive species.

People should be motivated to cultivate indigenous species. Necesssry action should be taken for

the naturally spreading species like Lantana camara, Eupatorium odoratum, Ipomea carnea

Mikania cordata, Ageratum conyzoides, Imperata cylindrica, Eichhornea crassipes, Pistia

strateotes etc. to eradicate them from the country or if not possible, to at least reduce their massive

spread in the environment. The enormous scale of threat from IAS is under appreciated in

Bangladesh. Bangladesh should take the problems of alien invasives more seriously. It is high time

that Bangladesh develops suitable methods and policies to deal with invasive alien species.

152

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Web sites

http://www.weeds.crc.org.au/crc for australian weed management

www.gisp.org/Protecting plants and plant hanbitats from invasive alien species

http://www.mdinvasivesp.org/invasive species of concern in maryland

http://edis.ifas.ufl.edu./Natural area weeds:air potato

http://esa.sdsc.edu(Fact sheet-Invasive species. Invasion!)

file: factsheet-invasive species.htm

(www.cal-ipc.org/don’t plant a pest!)

www.ucsusa.org/call to action on invasive species

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Author’s Biography

Mohammad Redowan was born on 27th Dec

1977 and brought up at Habigonj district in

Bangladesh. He obtained Bachelor of

Science degree with honours in 2004 and

Master of Science degree in 2005 in Forestry

from the Institute of Forestry and

Environmental Sciences in Chittagong

University (IFESCU), Bangladesh. On

March 2005 he joined as a lecturer in the

Department of Forestry and Environmental

Sciences (DFES) in the Shahjalal University of Science and Technology (SUST), the

largest public university of its kind in Bangladesh. Currently he is working as an Assistant

Professor. In 2008, Mr. Redowan received the European Union Erasmus Mundus

scholarship for the MSc in ‘Geo-information Science and Earth Observation for

Environmental Modelling and Management (GEM)’ a course jointly organized by a

consortium of four partner universities of four European countries. His teaching and

research points of interest include application of remote sensing and GIS in forestry,

research methods, forest and environmental modelling.

Contact

Home address:

Mohammad Redowan

C/O Mohammad Sirajul Islam

Holding No 72/73

Shayestanagar Traffic Point (east side)

Habigonj-3300

Bangladesh.

Professional address:

Mohammad Redowan

Department of Forestry and Environmental

Science

Shahjalal University of Science and

Technology (SUST)

Sylhet-3114, Bangladesh

Tel: PABX.0821-713491, 713850/ extn.-273

Fax: 88-0821-715257

Email: redowanforestry@yahoo.com

: redowan-for@sust.edu

Cell: +880-1818465634