L6 - Summary Questions

1. How is population growth rate calculated?

2. Differentiate between immigration and emigration.

3. List four factors affecting growth rate.

4. Which is the main factor that reduces fertility rate?

5. List four effects of urbanisation.

Lecture 7

Land and Human Populations

In the beginning:

• There were natural ecosystems

• The land was covered with forests

• There were many

species

• There was no waste

…Watersheds were forested

- Watersheds are also called drainage basins

or catchment areas

- They are areas of land that drain into

bodies of surface water

Functions of Watersheds- Forested watersheds act as giant sponges increasing infiltration

- They release water slowly moderating flooding and

maintaining stream flows in dry periods

- They control soil erosion improving water quality

- They are habitats for many species

- They regulate rainfall on a small scale

Rainfall Impact and Trees

Trees break the impact of rainfall on the soil thus reducing soil erosion.

Then came man:

• Man requires food, shelter and clothing

– Animals are hunted or reared for food and

clothing

– Forests are cleared for crops and housing

solutions

Early impact was minimal:

• Population levels were low

• Activities were for survival

• There was respect for nature

Jamaica Population Growth

0

500000

1000000

1500000

2000000

2500000

3000000

Year

Po

pu

lati

on

Competing uses for land:

• Agriculture (37%)

• Forests (31%; 3,402 km2)

• Housing and

Industry (5%)

• Mixed Use (27%)

• Total Area (10,964 km2)

Competing uses for land cont’d:

• Bauxite

• Roads

• Waste Disposal

• Burial Ground

Land Use Issues

Agriculture

- crops grown on ~11% of

Earth’s land

- 37% of Jamaica is agricultural land (1998)

Housing

- 1/5 of people in the

world have inadequate

housing

Road Construction

- the most serious impact, especially in LDCs, is the chain of events it starts

- roads make forests more accessible to farming, logging, cattle ranching, pests, diseases & biotic pollution

Waste Disposal

- landfills take up space

- deprive future generations of valuable resources

Jamaican Watersheds

- >1/3 have deteriorated

Causes of Jamaican Watershed Destruction

1. Unsuitable hillside agricultural practices

2. Illegal settlements on hillside lands

Causes of Jamaican Watershed Destruction cont’d

3. Deforestation due to illegal removal of trees for fuelwood, charcoal production, yam sticks and lumber

4. Forest fires caused by individuals

5. Unapproved quarrying and sand mining

Effects of Watershed Destruction

1. Massive soil loss through soil erosion

2. Siltation of drains and rivers

3. Destructive flooding downstream

4. Water pollution

5. Reduced water availability and quality

6. Loss of habitat for flora and fauna

Agriculture

- the growing of crops & the tending of livestock for subsistence, sale, or exchange

Three Main Types of Agriculture

1. Subsistence

2. Industrialised

3. Sustainable

Subsistence Agriculture

- production for family sustenance

- still practiced in many parts of the world

Subsistence Agriculture cont’d

Features of Low Input / Subsistence Agriculture:

• Human Labour

• Slash and Burn

• Shifting Cultivation

• Fallow Periods

• Animal Manure

• Mixed Cropping

                                            

            

Impact of Slash & Burn Cultivation

- also called Shifting Cultivation

- plots abandoned after 2-5 years due to loss of soil fertility

Innovations:

• The diesel engine

• Motor vehicles

• Medicines

• Pesticides

• Fertilizers

These led to:

• The Industrial revolution

• The Green Revolution

Industrialised Agriculture

- also called modern or advanced agriculture

- one crop or animal for sale

- use large amounts of :

a) fossil fuel energy

b) water

Industrialised agriculture has a greater impact on the environment than any other human activity

Industrialised Agriculture cont’d

Features of High Input/Conventional Agriculture:

• Mechanisation

• Monocropping

• Synthetic Pesticides

• Synthetic Fertilizers

• Genetic Engineering

• Irrigation

Mechanisation

- causes land degradation through soil compaction

- exacerbates

soil erosion

- causes decline in

soil fertility

- erosion damage causes decreased water quality

Soil Erosion

- movement of soil components, especially surface litter and topsoil, from one place to another, usually by exposure to wind or flowing water

Soil Erosion cont’d

Soil Erosion is caused by:

• Farming

• Logging

• Building

• Overgrazing

• Four-wheeling

Soil Erosion cont’d

The 3 Main Effects of Soil Erosion are:

1. Loss of topsoil

2. Reduced productivity

3. Surface water pollution

Monocropping:

- also called monoculture

- cultivation of a single crop, usually on a large

area of land

- simplifies ecosystems reducing biodiversity

- encourages the build up of pests thus increasing

the use of pesticides

- depletes the soil of nutrients

Use of Pesticides

Pesticide

- any chemical designed to kill or inhibit the growth of an organism that people consider undesirable

- fast-breeding insect species undergo natural selection and develop genetic resistance to chemical pesticides

                                             

                                

                                         

                       

Effects of Pesticide Use

- harmful to applications, consumers and the environment

- pollution of rivers & streams from pesticide runoff

- Pesticides linked to cancers and low sperm count

- persistent pesticides adhere to sediment and become bioaccumulated and biomagnified

                                             

                                

                                         

                       

Use of Fertilisers

Fertilisers

- substances that add plant nutrients to soil and improves its ability to grow crops

2 Main Types of Fertilisers:

- Organic Fertiliser

- Commercial Inorganic Fertiliser

Commercial Inorganic Fertiliser

- commercially prepared mixtures of plant nutrients applied to the soil to restore fertility and increase crop yields

- supply only 2 or 3 of the 20+ nutrients needed by plants

- leads to soil compaction

- water pollution

Disruption of Habitat

- over-fertilization of rivers caused by runoff of nitrates and phosphates

EFFECTS OF EUTROPHICATION

Genetic Engineering

- splices genes and recombines sequences of existing DNA molecules to produce DNA with new genetic characteristics

- transfers traits from one species to another to make new genetic combinations

Irrigation- The application of water to crops

- Types- Natural/Rainfall- Flood irrigation- Overhead/sprinkler- Drip irrigation (most efficient- 90%)

- Flood irrigation is wasteful and causes salinisation and waterlogging

Salinisation Due to Irrigation

Salinisation:- accumulation of salts in soil

that can eventually make the soil unable to support plant

growth

- lowers crop growth and yields

- kills crop plants & ruins the land

Other Impacts of Agriculture on the Environment

Overgrazing

- destruction of vegetation when too many grazing animals feed too long & exceed the carrying capacity of a rangeland area

Other Impacts of Agriculture on the Environment

Desertification

- process whereby agricultural productivity of land falls by 10%

- conversion of rangeland to desert-like land

Sustainable Agriculture

- Crops grown in harmony with the environment

- Health of humans and livestock important

- Environment important

- Workers important

- eg. Organic agriculture, biodynamic agriculture

Sustainable Agriculture Cont’d

Includes the use of:

- Companion cropping/mixed farming

- Soil conservation

- Addition of organic matter

- Use of alternatives to pesticides

- Social justice

Soil Conservation Methods

- methods used to:

◦ reduce soil erosion

◦ prevent depletion of soil nutrients

◦ restore nutrients

- most methods involve keeping the soil covered with vegetation

Soil Conservation Methods cont’d

Major Methods Include:

1. Conservation tillage

2. Contour farming, Terracing, Strip cropping, &

Alley cropping

3. Gully reclamation & Windbreaks

4. Land-Use Classification & Control

5. Maintaining & Restoring soil fertility

Soil Conservation Methods cont’d

1. Conservation Tillage- crop cultivation with little or no soil disturbance

▪ Minimum Tillage

▪ No-till Farming

Soil Conservation Methods cont’d

2. Contour Farming, Terracing, Strip Cropping & Alley Cropping

- used mainly on sloping land which is more prone to erosion

▪ Contour Farming- used on gently sloping land

Soil Conservation Methods cont’d

2. Contour Farming, Terracing, Strip Cropping & Alley Cropping cont’d

▪ Terracing- used on steeper slopes

Soil Conservation Methods cont’d

2. Contour Farming, Terracing, Strip Cropping & Alley Cropping cont’d

▪ Alley Cropping (Agroforestry)- planting crops with rows of trees on each

side

Soil Conservation Methods cont’d

3. Gully Reclamation & Windbreaks

▪ Gully Reclamation

Soil Conservation Methods cont’d

3. Gully Reclamation & Windbreaks cont’d

▪ Windbreaks (Shelterbelts)- row of trees planted to block wind flow

Soil Conservation Methods cont’d

4. Land Use Classification System

- describes different categories of land that are suitable and unsuitable for cultivation

Soil Conservation Methods cont’d

5. Maintaining & Restoring Soil Fertility

Involves the use of:

1. organic fertilizers

2. crop rotation

Alternatives to Pesticides

1. Cultivation Practices

- mow weeds

- rotate crops

- plant rows of hedges or trees

2. Resistant Varieties

- genetically resistant to certain pest insects, fungi and diseases

                                                                                          

Alternatives to Pesticides cont’d

3. Natural Enemies (Biological Control)

- predators, parasites & pathogens

can be encouraged or imported to regulate

pest populations

4. Birth Control (Reproductive Controls)

- males are lab-raised and

sterilised, then released to mate

Alternatives to Pesticides cont’d

5. Insect Sex Attractants (Pheromones)

- when a female is ready to mate she releases a pheromone (chemical

sex attractant)

6. Insect Hormones

- hormones: chemicals produced by an organism to control its

growth & development

Alternatives to Pesticides cont’d

7. Zapping Foods With Radiation

- gamma irradiation of foods is

used to kill insects & prevent them

from reproducing

8. Biopesticides

- plant & microbe toxins are

synthesised for mass production

Alternatives to Pesticides cont’d

9. Quarantine

- restriction of the importation of exotic

plant and animal material that

might harbour pests

10. Integrated Pest Management (IPM)

- biological and cultivation techniques

are used first, then biopesticides

when necessary

Organic Fertiliser

Organic Fertiliser

- organic materials, such as animal manure, applied as a source of plant nutrients

3 Basic Types of Organic Fertiliser

- Animal Manure

- Green Manure

- Compost

Organic Fertiliser cont’d

Animal Manure

- dung and urine of farm animals

- improves soil structure

- stimulates beneficial bacteria and fungi

Green Manure

- freshly-cut or still-growing vegetation that is ploughed into the soil

Organic Fertiliser cont’d

Compost

- partially decomposed organic plant and animal

matter

- made up of animal manure, topsoil, kitchen

scraps

- rich, natural fertilizer

Other Solutions to Land Pollution• sustaining existing forests and national parks

• restoring damaged areas

• support efforts to protect, expand, mend

Jamaica’s national park system

• support efforts to protect large areas of remaining

undeveloped lands

• reduce or eliminate the input of pollutants or

waste

Legislations

The Watersheds Protection Act

- law governing watersheds in Jamaica

- administered by NEPA

- reduces soil erosion

- ensures proper land use

- maintain optimum levels of groundwater

- promote regular flows in waterways

Other Legislation Relevant to Land Pollution

• Forest Act

• Rural Agricultural Development Act

• Water Resources Act

• Town and Country Planning Act

• Land Development and Utilisation Act

• Country Fires Act

• The Mining Act

• Wildlife Protection Act

L7- Summary Questions

1. What are the effects of mechanisation?

2. What is the name given to measures used to reduce soil erosion?

3. What is the difference between bioaccumulation and biomagnification?

4. Which type of irrigation is the most efficient?

5. List four alternatives to pesticide use.