biodiversity is the variation of life forms within a given

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Biodiversity is the variation oflifeforms within a given ecosystem,biome, or for theentire Earth. Biodiversity is often used as a measure of the health ofbiologicalsystems. The biodiversity found on Earth today consists of many millions of distinct

biological species, which is the product of nearly 3.5 billion years ofevolution.[1][2]

2010 is the International Year of Biodiversity.

International Year of Biodiversity

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The International Year of Biodiversity (IYB) is a year-long celebration ofbiological diversity and its value for life on Earth, taking place around the world in2010. Coinciding with the date of the 2010 Biodiversity Target, the Year was declared

by the 61st session of the United Nations General Assembly in 2006.

The International Year of Biodiversity will help raise awareness of the importance ofbiodiversity all over the world. Saving biodiversity requires an effort from everyone.Through activities and events in many countries, the global community will worktogether to ensure a sustainable future for us all.

[edit] Slogan

Biodiversity is life

Biodiversity is our life

[edit] Main messages

Humans are part of natures rich diversity and have the power to protect or destroy it.

Biodiversity, the variety of life on Earth, is essential to sustaining the living networksand systems that provide us all with health, wealth, food, fuel and the vital servicesour lives depend on.

Human activity is causing the diversity of life on Earth to be lost at a greatlyaccelerated rate. These losses are irreversible, impoverish us all and damage the lifesupport systems we rely on everyday. But we can prevent them.

2010 is the International Year of Biodiversity. Lets reflect on our achievements tosafeguard biodiversity and focus on the urgency of our challenge for the future. Now

is the time to act.

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[edit] Main goals

The celebrations of the International Year of Biodiversity are a unique opportunity toraise public awareness about the vital role of biodiversity sustaining life on Earth,supporting ecosystem services and of its importance to human wellbeing and povertyreduction.

The main goals of the International Year of Biodiversity are to:

Enhance public awareness of the importance of conserving biodiversity and ofthe underlying threats to biodiversity

Raise awareness of the accomplishments to save biodiversity that have alreadybeen realized by communities and governments

Promote innovative solutions to reduce the threats to biodiversity Encourage individuals, organizations and governments to take immediate

steps to halt biodiversity loss Start dialogue between stakeholders for the steps to be taken in the post-2010

period.

Every person in the world is invited to participate, to act and to share experiences withothers.

[edit] Background

The United Nations General Assembly declared 2010 as the International Year of

Biodiversity (resolution 61/203). This year coincides with the 2010 BiodiversityTarget adopted by the Parties to the Convention on Biological Diversity and by Headsof State and government at the World Summit for Sustainable Development inJohannesburg in 2002.

The Secretariat of the Convention on Biological Diversity, based in Montreal,Canada, is coordinating the International Year of Biodiversity.

Established at the Earth Summit in Rio de Janeiro in 1992, the Convention onBiological Diversity (CBD) is an international treaty for the conservation andsustainable use of biodiversity and the equitable sharing of the multiple benefits of

biodiversity. The CBD has near-universal participation, with 191 Parties.

[edit] Celebrations around the world

At the international level International organizations will celebrate the year through anumber of events that highlight what is being done.

By Governments

Governments are the main coordinators of the celebrations. While governments are

making plans, here are some ideas of what to do:

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Extensive website and information materials distributed widely; Coordinated series of celebrations at national, regional and local levels; Extensive support to events created by civil society organizations and others; National support to promote 2010 Success Stories, including recognition

through prizes and certificates of exemplary actions by citizens in support for

biodiversity; Exhibition on 2010 Success Stories at the CEPA fair, at COP-10; Release of National Reports and National Biodiversity Strategies and Action

Plans (NBSAPs); Extensive mobilization of Natural History Museums, including support for the

organization of travelling exhibitions; Sponsor and publicize activities organized by biodiversity-related scientific

societies and research centres; Partnerships with broadcasters, including sponsorship of film festivals; Support for local biodiversity monitoring programmes; Holding of youth events, including symposia, competitions, etc.; Integration of biodiversity issues into the Education system.

By NGOs

Adapt and adopt the International Year of Biodiversity messages and thendiffuse them in your networks.

Highlight and promote your own 2010 success stories. Provide support and resources to national events including on:

o the International Day for Biodiversity 22 May.

o the World Environment Day, 5 June, and other events.

Build links between biodiversity and other environmental and developmentthemes. Organise events at key international meetings. Become involved in the Convention on Biological Diversity process.

By anyone who wishes to participateAs part of the International Year of Biodiversity, people around the world are invitedto submit ideas of biodiversity-friendly practices, which:

have a positive impact on biodiversity. promote the sustainable use of biodiversity.

promote innovative solutions to biodiversity-related problems. motivate individual action to protect biodiversity. can be adapted and imitated by others. raise peoples awareness of biodiversity. show the relationship between biodiversity and other themes.

[edit] Biodiversity-friendly practices in everyday life

Everyone can help biodiversity and the environment by living in a sustainablemanner. How are we affecting our surrounding environment? How do our actions

affect more distant ecosystems and other people? To consume less, waste less, reuse

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and recycle are only the first steps to help biodiversity. Simple everyday activitiesmake a difference.

[edit] What can I do?

Learn about biodiversity and environmental issues in your area and in your country.You need to know a bit about what biodiversity is before you can act. You can

participate in the International Year of Biodiversity at the local level by joiningenvironmental NGOs and volunteering in environmental actions. Saving biodiversitystarts in the community. Find out about the celebrations in your country and

participate. If there are no celebrations in your area, you can organize biodiversity-related activities, conferences and events yourself. Your biggest contribution thoughis in your daily actions. Thoughtful consumption that takes into account the impact ofyour actions on the ecosystems of our planet is the way you can conserve andsustainably use the biodiveristy of our planet.

[edit] Etymology

The term was used first by wildlife scientist and conservationist Raymond F.Dasmann in a lay book[3] advocating nature conservation. The term was not widelyadopted for more than a decade, when in the 1980s it and "biodiversity" came intocommon usage in science and environmental policy. Use of the term by ThomasLovejoy in the Foreword to the book[4] credited with launching the field ofconservation biology introduced the term along with "conservation biology" to thescientific community. Until then the term "natural diversity" was used in conservationscience circles, including by The Science Division ofThe Nature Conservancyin animportant 1975 study, "The Preservation of Natural Diversity." By the early 1980sTNC's Science program and its head Robert E. Jenkins, Lovejoy, and other leadingconservation scientists at the time in America advocated the use of "biologicaldiversity" to embrace the object of biological conservation.

The term's contracted form biodiversity may have been coined by W.G. Rosen in1985 while planning theNational Forum on Biological Diversity organized by the

National Research Council(NRC) which was to be held in 1986, and first appeared in

a publication in 1988 when entomologist E. O. Wilson used it as the title of theproceedings[5] of that forum.[6]

Since this period both terms and the concept have achieved widespread use amongbiologists, environmentalists, political leaders, and concerned citizens worldwide. Theterm is sometimes used to equate to a concern for the natural environment and natureconservation. This use has coincided with the expansion of concern overextinctionobserved in the last decades of the 20th century.

A similar concept in use in the United States, besides natural diversity, is the term"natural heritage." It pre-dates both terms though it is a less scientific term and more

easily comprehended in some ways by the wider audience interested in conservation."Natural Heritage" was used when Jimmy Carterset up the Georgia Heritage Trust

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There are many different ways to measure genetic diversity. The modern causes forthe loss of animal genetic diversity have also been studied and identified. [1][2] A 2007study conducted by theNational Science Foundationfound that genetic diversity and

biodiversity are dependent upon each other -- that diversity within a species isnecessary to maintain diversity among species, and vice versa. According to the lead

researcher in the study, Dr. Richard Lankau, "If any one type is removed from thesystem, the cycle can break down, and the community becomes dominated by a singlespecies."[3]

[edit] Survival and adaptation

Genetic diversity plays a very important role in survival and adaptability of a speciesbecause when a speciess environment changes, slight gene variations are necessary toproduce changes in the organisms' anatomy that enables it to adapt and survive. Aspecies that has a large degree of genetic diversity among its population will have

more variations from which to choose the most fit alleles. Increase in genetic diversityis also essential for an organism to evolve. Species that have very little geneticvariation are at a great risk. With very little gene variation within the species, healthyreproduction becomes increasingly difficult, and offspring often deal with similar

problems to those ofinbreeding.[4] The vulnerability of a population to certain types ofdiseasescan also increase with reduction in genetic diversity.

[edit] Agricultural relevance

When humans initially started farming, they used selective breeding to pass ondesirable traits of the crops while omitting the undesirable ones. Selective breedingleads to monocultures: entire farms of nearly genetically identical plants. Little to nogenetic diversity makes crops extremely susceptible to widespread disease. Bacteriamorph and change constantly. When a disease causing bacterium changes to attack aspecific genetic variation, it can easily wipe out vast quantities of the species. If thegenetic variation that the bacterium is best at attacking happens to be that whichhumans have selectively bred to use for harvest, the entire crop will be wiped out.[5]

A very similar occurrence is the cause of the infamousPotato Faminein Ireland.Since new potato plants do not come as a result of reproduction but rather from piecesof the parent plant, no genetic diversity is developed, and the entire crop is essentiallya clone of one potato, it is especially susceptible to an epidemic. In the 1840s, muchof Irelands population depended on potatoes for food. They planted namely thelumper variety of potato, which was susceptible to a rot-causing plasmodiophoridcalledPhytophthora infestans.[6] Thisplasmodiophorid destroyed the vast majority ofthe potato crop, and left tens of thousands of people to starve to death.

[edit] Coping with poor genetic diversity

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The natural world has several ways of preserving or increasing genetic diversity.Among oceanicplankton, viruses aid in the genetic shifting process. Ocean viruses,which infect the plankton, carry genes of other organisms in addition their own. Whenavirus containing the genes of one cell infects another, the genetic makeup of thelatter changes. This constant shift of genetic make-up helps to maintain a healthy

population of plankton despite complex and unpredictable environmental changes.[7]

Cheetahs are a threatened species. Extremely low genetic diversity and resulting poorsperm quality has made breeding and survivorship difficult for cheetahs - only about5% of cheetahs survive to adulthood.[8] About 10,000 years ago, all but the jubatusspecies of cheetahs died out. The species encountered apopulation bottleneckandclose family relatives were forced to mate with each other, orinbreed.[9]However, ithas been recently discovered that female cheetahs can mate with more than one male

per litter of cubs. They undergo induced ovulation, which means that a new egg isproduced every time a female mates. By mating with multiple males, the motherincreases the genetic diversity within a single litter of cubs.[10]

species diversity

Species diversity



Species diversity is an index that incorporates the number of species in an area andalso their relative abundance. It is generally a much more useful value than speciesrichness.

The most common index of species diversity is a family of equations calledSimpson'sDiversity Index[1].

Here is one such example

D = (n / N)2

Where n is the total number of organisms of a particular species and N is the totalnumber of organisms of all species. D is the value of diversity. It can range between 0and 1, where 0 is infinite diversity, and 1 is the least diverse an ecosystem can

possibly be (i.e. only one species present).

Humans have a huge effect on species diversity; the main reasons are:- Destruction, Modification, and/or Fragmentation of Habitat- Introduction of Exotic Species- Overharvest

- Global Climate Change

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ecosystem diversity

Ecosystem diversity



Ecosystem diversity refers to the diversity of a place at the level ofecosystems. It iscontrasted withbiodiversity, which refers to variation in species rather thanecosystems.

This multilevel conception is consistent with the early use of "biological diversity" inWashington. D.C. and international conservation organizations in the late 1960sthrough 1970's, by Raymond F. Dasmann who apparently coined the term andThomas E. Lovejoy who later introduced it to the wider conservation and sciencecommunities. An explicit definition consistent with this interpretation was first givenin a paper by Bruce A. Wilcox commissioned by the International Union for theConservation of Nature and Natural Resources(IUCN) for the 1982 World NationalParks Conference in Bali [7] The definition Wilcox gave is "Biological diversity is thevariety of life forms...at all levels of biological systems (i.e., molecular, organismic,

population, species and ecosystem)..." Subsequently, the 1992United NationsEarth

Summit in Rio de Janeiro defined "biological diversity" as "the variability amongliving organisms from all sources, including, 'inter alia',terrestrial,marine, and otheraquatic ecosystems, and the ecological complexes of which they are part: this includesdiversity within species, between species and of ecosystems". This is, in fact, theclosest thing to a single legally accepted definition of biodiversity, since it is thedefinition adopted by the United Nations Convention on Biological Diversity.

The current textbook definition of "biodiversity" is "variation of life at all levels ofbiological organization".[8]

Forgeneticists, biodiversity is the diversity of genes and organisms. They study

processes such as mutations, gene exchanges, and genome dynamics that occur at theDNA level and generate evolution. Consistent with this, along with the abovedefinition the Wilcox paper stated "genes are the ultimate source of biologicalorganization at all levels of biological systems..."

[edit] Measurement

Main article: Measurement of biodiversity

Measurement of biodiversity


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Jump to: navigation,searchMain article: Biodiversity

Polar bears on the sea ice of the Arctic Ocean, near the north pole.

A variety of objective measures have been created in order toempiricallymeasurebiodiversity. Each measure of biodiversity relates to a particular use of the data. Forpractical conservationists, measurements should include a quantification of values thatare commonly-shared among locally affected organisms, including humans. Forothers, a more economically defensible definition should allow the ensuring ofcontinued possibilities for both adaptation and future use by humans, assuringenvironmental sustainability.

As a consequence, biologists argue that this measure is likely to be associated with thevariety of genes. Since it cannot always be said which genes are more likely to prove

beneficial, the best choice forconservation is to assure the persistence of as manygenes as possible. For ecologists, this latter approach is sometimes considered toorestrictive, as it prohibits ecological succession.

Biodiversity is usually plotted as taxonomic richness of a geographic area, with somereference to a temporal scale. Whittaker[1] described three common metrics used tomeasure species-level biodiversity, encompassing attention tospecies richness orspecies evenness:

Species richness - the least sophisticated of the indices available. Simpson index Shannon-Wiener index

Recently, another new index has been invented called theMean Species AbundanceIndex (MSA); this index calculates the trend in population size of a cross section ofthe species. It does this in line with the CBD 2010 indicator for species abundance.[2]

There are three other indices which are used by ecologists:

Alpha diversity refers to diversity within a particular area, community orecosystem, and is measured by counting the number of taxa within theecosystem (usually species)

Beta diversity is species diversity between ecosystems; this involvescomparing the number of taxa that are unique to each of the ecosystems.

Gamma diversity is a measurement of the overall diversity for differentecosystems within a region.

A variety of objective measures have been created in order to empirically measurebiodiversity. Each measure of biodiversity relates to a particular use of the data. Forpractical conservationists, measurements should include a quantification of values that

are commonly-shared among locally affected organisms, including humans. Forothers, a more economically defensible definition should allow the ensuring of

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continued possibilities for both adaptation and future use by humans, assuringenvironmental sustainability.

[edit] Distribution

A conifer forest in the Swiss Alps (National Park).

Selection bias continues to bedevil modern estimates of biodiversity. In 1768 Rev.Gilbert Whitesuccinctly observed of his Selborne, Hampshire "all nature is so full,that that district produces the most variety which is the most examined."[9]

Nevertheless, biodiversity is not distributed evenly on Earth. It is consistently richerin the tropics and in other localized regions such as the Cape Floristic Province. Asone approaches polar regions one generally finds fewer species. Flora and faunadiversity depends on climate, altitude,soils and the presence of other species. In theyear 2006 large numbers of the Earth's species were formally classified as rare orendangeredorthreatened species; moreover, many scientists have estimated that thereare millions more species actually endangered which have not yet been formallyrecognized. About 40 percent of the 40,177 species assessed using the IUCN Red Listcriteria, are now listed as threatened species with extinction - a total of 16,119species.[10]

Even though biodiversity declines from the equator to the poles in terrestrialecoregions, whether this is so in aquatic ecosystemsis still a hypothesis to be tested,

especially in marine ecosystemswhere causes of this phenomenon are unclear.

[11]

Inaddition, particularly in marine ecosystems, there are several well stated cases wherediversity in higher latitudes actually increases. Therefore, the lack of information on

biodiversity ofTropics andPolar Regions prevents scientific conclusions on thedistribution of the worlds aquatic biodiversity.

Abiodiversity hotspotis a region with a high level ofendemicspecies. Thesebiodiversity hotspots were first identified by Dr.Norman Myers in two articles in thescientific journal The Environmentalist.[12][13]Dense human habitation tends to occurnear hotspots. Most hotspots are located in thetropicsand most of them are forests.

Brazil's Atlantic Forest is considered a hotspot of biodiversity and contains roughly20,000 plant species, 1350 vertebrates, and millions of insects, about half of whichoccur nowhere else in the world. The island ofMadagascarincluding the uniqueMadagascar dry deciduous forests and lowland rainforests possess a very high ratio ofspecies endemism and biodiversity, since the island separated from mainland Africa65 million years ago, most of the species and ecosystems have evolved independently

producing unique species different from those in other parts of Africa.

Many regions of high biodiversity (as well as high endemism) arise from veryspecialized habitats which require unusual adaptation mechanisms. For example the

peatbogs of Northern Europe.

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Since the stone age, species loss has been accelerated above the geological rate byhuman activity. The rate of species extinction is difficult to estimate, but it has beenestimated that species are now being lost at a rate approximately 100 times as fast asis typical in the geological record, or perhaps as high as 10 000 times as fast.[19] Tofeed such a large population, more land is being transformed from wilderness with

wildlife into agricultural, mining, lumbering, and urban areas for humans.

Non-material benefits that are obtained from ecosystems include spiritual andaesthetic values , knowledge systems and the value of education.

[edit] Agriculture

The economic value of the reservoir of genetic traits present in wild varieties andtraditionally grown landraces is extremely important in improving crop

performance[citation needed]. Important crops, such as the potato and coffee, are oftenderived from only a few genetic strains[citation needed]. Improvements in crop plants overthe last 250 years have been largely due to harnessing the genetic diversity present inwild and domestic crop plants[citation needed]. Interbreeding crops strains with different

beneficial traits has resulted in more than doubling crop production in the last 50years as a result of the Green Revolution[citation needed].

Crop diversity is also necessary to help the system recover when the dominant croptype is attacked by a disease:

The Irish potato blight of 1846, which was a major factor in the deaths of amillion people and migration of another million, was the result of planting

only two potato varieties, both of which were vulnerable. When rice grassy stunt virus struck rice fields from Indonesia to India in the

1970s. 6273 varieties were tested for resistance.[20] One was found to beresistant, an Indian variety, known to science only since 1966.[20]This varietyformed a hybrid with other varieties and is now widely grown.[20]

Coffee rust attacked coffee plantations in Sri Lanka, Brazil, and CentralAmerica in 1970. A resistant variety was found in Ethiopia.[21] Although thediseases are themselves a form of biodiversity.

Amazon Rainforest in Brazil

Monoculture, the lack of biodiversity, was a contributing factor to several agriculturaldisasters in history, the European wine industry collapse in the late 1800s, and theUSSouthern Corn Leaf Blightepidemic of 1970.[22] See also: Agricultural biodiversity

Higher biodiversity also controls the spread of certain diseases as pathogens will needto adapt to infect different species[citation needed].

Biodiversity provides food for humans[citation needed]. Although about 80 percent of ourfood supply comes from just 20 kinds of plants[citation needed], humans use at least 40,000

species of plants and animals a day[citation needed]

. Many people around the world dependon these species for their food, shelter, and clothing [citation needed]. There is untapped

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it provides are considered to be fundamental to healthy economic systems. The degreeto which biodiversity supports business varies between regions and between economicsectors, however the importance of biodiversity to issues of resource security (waterquantity and quality, timber, paper and fibre, food and medicinal resources etc) areincreasingly recognized as universal.[37][38][39] As a result, the loss of biodiversity is

increasingly recognized as a significant risk factor in business development and athreat to long term economic sustainability. A number of case studies recentlycompiled by the World Resources Institute demonstrate some of these risks asidentified by specific industries.[40]

Eagle Creek, Oregon hiking

[edit] Other ecological services

See also: Ecological effects of biodiversity

Ecological effects of biodiversity



The diversity ofspeciesand genes in ecological communities affects the functioningof these communities. These ecological effects of biodiversity in turn affect both

climate changethrough enhanced greenhouse gases,aerosols and loss of land cover,and biological diversity, causing a rapid loss ofecosystemsandextinctionsofspeciesand local populations. The current rate of extinction is sometimes considered a massextinction, with current species extinction rates on the order of 100 to 1000 times ashigh as in the past.[1]

The two main areas where the effect of biodiversity on ecosystem function have beenstudied are the relationship between diversity and productivity, and the relationship

between diversity and community stability. More biologically diverse communitiesappear to be more productive (in terms ofbiomass production) than are less diversecommunities, and they appear to be more stable in the face of perturbations.

Also animals that inhabit an area may alter the surviving conditions by factorsassimilated by climate.

[edit] Definitions of diversity, productivity, and

stability

In order to understand the effects that changes inbiodiversitywill have on ecosystemfunctioning, it is important to define some terms. Biodiversity is not easily defined,

but may be thought of as the number and/or evenness ofgenes, species, and

ecosystems in a region. This definition includes genetic diversity, or the diversity of

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genes within a species, species diversity, or the diversity of species within a habitat orregion, and ecosystem diversity, or the diversity of habitats within a region.

Two things commonly measured in relation to changes in diversity are productivityandstability. Productivity is a measure of ecosystem function. It is generally

measured by taking the total abovegroundbiomass of all plants in an area. Manyassume that it can be used as a general indicator of ecosystem function and that totalresource use and other indicators of ecosystem function are correlated with

productivity.

Stability is much more difficult to define, but can be generally thought of in twoways. General stability of a population is a measure that assumes stability is higher ifthere is less of a chance of extinction. This kind of stability is generally measured bymeasuring the variability of aggregate community properties, like total biomass, overtime [2] The other definition of stability is a measure of resilience and resistance,where an ecosystem that returns quickly to anequilibrium after a perturbation or

resists invasion is thought of as more stable than one that doesn't.[3]

[edit] Productivity and stability as indicators of

ecosystem health

The importance of stability in community ecology is clear. An unstable ecosystemwill be more likely to lose species. Thus, if there is indeed a link between diversityand stability, it is likely that losses of diversity could feedback on themselves, causingeven more losses of species. Productivity, on the other hand, has a less clearimportance in community ecology. In managed areas like cropland, and in areaswhere animals are grown or caught, increasing productivity increases theeconomicsuccess of the area and implies that the area has become more efficient, leading to

possible long term resource sustainability.[4] It is more difficult to find the importanceof productivity in natural ecosystems. This will be discussed in more detail later.

[edit] Does biodiversity have value?

Beyond the value biodiversity has in regulating and stabilizing ecosystem processes,there are direct economic consequences of losing diversity in certain ecosystems andin the world as a whole. Losing species means losing potentialfoods,medicines,

industrial products, and tourism, all of which have a direct economic effect on peopleslives.[5] For more information, see the economic role of biodiversity.

[edit] Effects of diversity on community productivity

[edit] How species diversity may influence productivity

Complementarity Plant species coexistence is thought to be the result ofniche partitioning, or differences in resource requirements among species. Bycomplementarity, a more diverse plant community should be able to use

resources more completely, and thus be more productive. [4][6] Also called nichedifferentiation, this mechanism is a central principle in the functional group

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approach, which breaks species diversity down into functional components. [7][8]

FacilitationFacilitationis a mechanism whereby certain species help or allowother species to grow by modifying the environment in a way that is favorableto a co-occurring species.[9] Plants can interact through an intermediary like

nitrogen, water, temperature, space, or interactions with weeds or herbivoresamong others. Some examples of facilitation include large desert perennialsacting as nurse plants, aiding the establishment of young neighbors of otherspecies by alleviating water and temperature stress,[10] and nutrient enrichment

by nitrogen-fixers such as legumes. The Sampling Effect The sampling effect of diversity can be thought of as

having a greater chance of including a species of greatest inherent productivityin a plot that is more diverse. This provides for a composition effect on

productivity, rather than diversity being a direct cause. However, the samplingeffect may in fact be a compilation of different effects. The sampling effectcan be separated into the greater likelihood of selecting a species that is 1)

adapted well to particular site conditions, or 2) of a greater inherentproductivity. Additionally, one can add to the sampling effect a greaterlikelihood of including 3) a pair of species that highly complement each other,or 4) a certain species with a large facilitative effect on other members of thecommunity.

[edit] Review of data

Field experiments to test the degree to which diversity affects community productivityhave found many things, but many long term studies ingrassland ecosystems have

found that diversity does indeed enhance the productivity of ecosystems.

[11][12][13]

Evidence of the relationship has also been found in grassland microcosms. However,these different studies have come to different conclusions as to whether the cause wasdue more to diversity or to species composition. Recent mathematical models havehighlighted the importance of ecological context in unraveling this problem. Somemodels have indicated the importance ofdisturbancerates and spatialheterogeneity ofthe environment,[14] others have indicated that the time since disturbance and thehabitat's carrying capacity can cause differing relationships.[15] Each ecologicalcontext should yield not only a different relationship, but a different contribution tothe relationship due to diversity and to composition.

[edit] Implications for ecology/future research

In order to correctly identify the consequences of diversity on productivity and otherecosystem processes, many things must happen. First, it is imperative that scientistsstop looking for a single relationship. It is obvious now from the models, the data, andthe theory that there is no one overarching effect of diversity on productivity.Scientists must try to quantify the differences between composition effect anddiversity effects, as many experiments never quantify the final realized speciesdiversity (instead only counting numbers of species of seeds planted) and confound asampling effect for facilitators (a compositional factor) with diversity effects.

Relative amounts ofoveryielding(or how much more a species grows when grownwith other species than it does in monoculture) should be used rather than absolute

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amounts as relative overyielding can give clues as to the mechanism by whichdiversity is influencing productivity, however if experimental protocols areincomplete, one may be able to indicate the existence of a complementary orfacilitative effect in the experiment, but not be able to recognize its cause.Experimenters should know what the goal of their experiment is, that is, whether it is

meant to inform natural or managed ecosystems, as the sampling effect may only be areal effect of diversity in natural ecosystems (managed ecosystems are composed tomaximize complementarity and facilitation regardless of species number). Byknowing this, they should be able to choose spatial and temporal scales that areappropriate for their experiment. Lastly, to resolve the diversity-function debate, it isadvisable that experiments be done with large amounts of spatial and resourceheterogeneity and environmental fluctuation over time, as these types of experimentsshould be able to demonstrate the diversity-function relationship more easily.[4]

[edit] Effects of diversity on community stability

[edit] How species diversity may influence community stability

Averaging Effect If all species have differential responses to changes in theecosystem over time, then the averaging of these responses will cause a moretemporally stable ecosystem if more species are in the ecosystem.[2]. Thiseffect is a statistical effect due to summingrandomvariables.

Negative Covariance Effect If some species do better when other species arenot doing well, then when there are more species in the ecosystem, theiroverall variance will be lower than if there were fewer species in the system.This lower variance indicates higher stability. [16] This effect is a consequence

ofcompetitionas highly competitive species will negatively covary. Insurance Effect If an ecosystem contains more species then it will have a

greater likelihood of having redundant stabilizing species, and it will have agreater number of species that respond differently to perturbations. This willenhance an ecosystem's ability tobufferperturbations.[17]

Resistance to Invasion Diverse communities may use resources morecompletely than simple communities because of a diversity effect forcomplementarity. Thus invaders may have reduced success in diverseecosystems, or there may be a reduced likelihood that an invading species willintroduce a new property or process to a diverse ecosystem.[8][18][19]

Resistance to Disease A decreased number of competing plant species mayallow the abundances of other species to increase, facilitating the spread ofdiseases of those species. [18][19][20]

[edit] Review of temporal stability data

Models have predicted that empirical relationships between temporal variation ofcommunity productivity and species diversity are indeed real, and that they almosthave to be. Some temporal stability data can be almost completely explained by theaveraging effect by constructing null models to test the data against. [2][11] Competition,which causes negative covariances, only serves to strengthen these relationships.

[edit] Review of resistance/resilience stability data

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This area is more contentious than the area of temporal stability, mostly because somehave tried generalizing the findings of the temporal stability models and theory tostability in general. While the relationship between temporal variations in productivityand diversity has a mathematical cause, which will allow the relationship to be seenmuch more often than not, it is not the case with resistance/resilience stability. Some

experimenters have seen a correlationbetween diversity and reduced invasibility,though many have also seen the opposite.[21]The correlation between diversity anddisease is also tenuous, though theory and data do seem to support it. [20]

[edit] Implications for ecology/future research

In order to more fully understand the effects of diversity on the temporal stability ofecosystems it is necessary to recognize that they are bound to occur. By constructingnull models to test the data against (as in Doak et al. 1998[2]) it becomes possible tofind situations and ecological contexts where ecosystems become more or less stablethan they should be. Finding these contexts would allow for mechanistic studies intowhy these ecosystems are more stable, which may allow for applications inconservationmanagement.

More importantly more complete experiments into whether diverse ecosystemsactually resist invasion and disease better than their less diverse equivalents asinvasion and disease are two important factors that lead to species extinctions in the

present day.

[edit] Theory and preliminary effects from examining

food websOne major problem with both the diversity-productivity and diversity-stability debatesdiscussed up to this point is that both focus on interactions at just a singletrophiclevel. That is, they are concerned with only one level of the food web, namely plants.Other research, unconcerned with the effects of diversity, has demonstrated strongtop-down forcing of ecosystems (seekeystone species). There is very little actual dataavailable regarding the effects of different food webs, but theory helps us in this area.First, if a food web in an ecosystem has a lot of weakinteractions between differentspecies, then it should have more stable populations and the community as a wholeshould be more stable.[3] If upper levels of the web are more diverse, then there will be

lessbiomass in the lower levels and if lower levels are more diverse they will betterbe able to resist consumption and be more stable in the face of consumption. Also,top-down forcing should be reduced in less diverse ecosystems because of the bias forspecies in higher trophic levels to go extinct first. [22] Lastly, it has recently been shownthat consumerscan dramatically change the biodiversity-productivity-stabilityrelationships that are implied by plants alone.[23] Thus, it will be important in thefuture to incorporate food web theory into the future study of the effects of

biodiversity. In addition this complexity will need to be addressed when designingbiodiversity management plans.

[edit] Conclusions

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It is imperative that we come to a realization that there is no single overarching effectof diversity on either productivity or stability. The realized effects will depend heavilyon environmental context and the time scale over which the effects are studied.However, it has become obvious that biodiversity is indeed important for bothmanaged and natural ecosystems, though the relative contributions of diversity and

composition remain unclear. It is therefore necessary for legislators to understand thebasic science in order to maintain diversity at its current levels. If current humangrowth and resource management patterns do not change, it is likely that we will losemany important species, and the ecosystems of the world may never recover.

Biodiversity provides many ecosystem services that are often not readily visible. Itplays a part in regulating the chemistry of ouratmosphere and water supply.Biodiversity is directly involved in water purification, recyclingnutrients and

providing fertile soils. Experiments with controlled environments have shown that

humans cannot easily build ecosystems to support human needs; for example insectpollination cannot be mimicked by human-made construction, and that activity alonerepresents tens of billions of dollars in ecosystem services per annum to humankind.

The stability of ecosystems is also related to biodiversity, with higher biodiversityproducing greater stability over time, reducing the chance that ecosystem services willbe disrupted as a result of disturbances such as extreme weather events or humanexploitation.

[edit] Leisure, cultural and aesthetic value

Many people derive value from biodiversity through leisure activities such as hiking,birdwatchingor natural history study. Biodiversity has inspired musicians, painters,sculptors, writers and other artists. Many cultural groups view themselves as anintegral part of the natural world and show respect for other living organisms.

Popular activities such as gardening, caring for aquariums and collecting butterfliesare all strongly dependent on biodiversity. The number of species involved in such

pursuits is in the tens of thousands, though the great majority do not enter mainstreamcommercialism.

The relationships between the original natural areas of these often 'exotic' animals andplants and commercial collectors, suppliers, breeders, propagators and those whopromote their understanding and enjoyment are complex and poorly understood. Itseems clear, however, that the general public responds well to exposure to rare andunusualorganismsthey recognize their inherent value at some level. A familyouting to thebotanical gardenor zoo is as much an aesthetic or cultural experience asit is an educational one.

Philosophically it could be argued that biodiversity has intrinsic aesthetic and spiritualvalue to mankind in and of itself. This idea can be used as a counterweight to thenotion that tropical forestsand other ecological realms are only worthy of

conservation because they may contain medicines or useful products.

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An interesting point is that evolved DNA embodies knowledge,[41]and thereforedestroying a species resembles burning a book, with the caveat that the book is ofuncertain depth and importance and may in fact be best used as fuel.

[edit] Number of species

Main article: Undiscovered species

Undiscovered and discovered species

Species


(Redirected from Undiscovered species)

Jump to: navigation,searchFor other uses, see Species (disambiguation).

The hierarchy ofbiological classification's eight majortaxonomic ranks. Agenuscontains one or more species. Intermediate minor rankings are not shown.

Inbiology, a species is:

ataxonomic rank(the basic rank ofbiological classification) or a unit at that rank (in which case thepluralis "species". This is sometimes

abbreviated: "spec." or "sp."singular, or "spp."plural).

There are many definitions of what kind of unit a species is (or should be). A commondefinition is that of a group of organisms capable of interbreeding and producingfertile offspring of both genders, and separated from other such groups with whichinterbreeding does not (normally) happen. Other definitions may focus on similarityof DNA or morphology. Some species are further subdivided into subspecies, andhere also there is no close agreement on the criteria to be used.

[edit] Biologists' working definition

A usable definition of the word "species" and reliable methods of identifyingparticular species is essential for stating and testing biological theories and formeasuringbiodiversity. Traditionally, multiple examples of a proposed species must

be studied for unifying

biodiversity is the variation of life forms within a given

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