Land and Human Populations

MUCH OF JAMAICA’S LAND MASS IS CONSIDERED AS ONE LARGE

WATERSHED.

- Watersheds are also called drainage basins

or catchment areas

- They are areas of land that drain water into

bodies of surface water.

- Jamaica’s land mass is divided into 26

watersheds to facilitate easier management.

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 thereby improving water quality

• They are habitats for many species

• They regulate rainfall on a small scale (via transpiration)

Functions of Watersheds

Rainfall Impact and Trees

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

Competing uses for land:

• Forests (31%)

• Agriculture (37%)

• Housing and

Industry (5%)

• Roads

• Waste Disposal

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 cont’d

Features of Low Input / Subsistence Agriculture:

• Human Labour

• Slash and Burn

• Shifting Cultivation

• Fallow Periods

• Animal Manure

• Mixed Cropping

                                                  

      

Industrialised Agriculture- also called modern or advanced agriculture

- one crop (monoculture / monocropping) or

animal for sale

- use large amounts of :

a) fossil fuel energy

b) water

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 the environment

- Pesticides linked to cancers and low sperm count

- persistent pesticides adhere to sediment and become bioaccumulated and biomagnified

- mobile

                                             

                                

                                                 

               

Use of Fertilizers

Fertilizers

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

2 Main Types of Fertilizers:

- Organic Fertilizer

- Commercial Inorganic Fertilizer

Commercial Inorganic Fertilizer

- 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

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.

Impacts of Agriculture on the Environment cont’d

1. Chemical Damage

- pollution of rivers & streams from pesticide

and fertilizer runoff

- nitrates & phosphates in waterbodies,

drinking water, food & air

Impacts of Agriculture on the Environment cont’d

2. Disruption of Habitat

- over-fertilization of rivers caused by runoff of nitrates and phosphates (eutrophication)

Impacts of Agriculture on the Environment cont’d

3. Loss of Biodiversity

- reduction in nutrient recycling soil organisms

- loss of plant genetic diversity

- endangerment & extinction of wildlife

Impacts of Agriculture on the Environment cont’d

4. 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 (causes rotting of roots) &

ruins the land

Impacts of Agriculture on the Environment cont’d

5. Desertification

- process whereby agricultural productivity of land falls by 10%

- conversion of rangeland to desert-like land

Caused by:

- mechanization, salinization, overgrazing,

shifting agriculture

Impacts of Agriculture on the Environment cont’d

6. Slash & Burn Cultivation

- also called Shifting Cultivation

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

Impacts of Agriculture on the Environment cont’d

7. Overgrazing

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

Sustainable Agriculture

- Crops grown in harmony with the

environment

- Health of humans and livestock important

- Environment important

- Workers important

- e.g. Organic agriculture

Sustainable Agriculture Cont’d

Includes the use of:

- Companion cropping/mixed farming

- Soil conservation (preventing soil erosion)

- Addition of organic matter

- Use of alternatives to pesticides

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. Windbreaks / Shelterbelts

4. 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

http://www.monsanto.com/biotech-gmo/images/story/pf/benefits_topic_pf.jpg

MINIMUM TILLAGEhttp://www.ck12.org/ck12/images?id=113628

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

CONTOUR FARMING

http://farm3.static.flickr.com/2190/2873940406_72cda96baa_o.jpg

Soil Conservation Methods cont’d

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

▪ Terracing- used on steeper slopes

TERRACINGTERRACINGhttp://static.panoramio.com/photos/original/4106996.jpg

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 or amongst trees of the forest2. Contour Farming, Terracing, Strip Cropping

& Alley Cropping cont’d

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

side or amongst trees of the forest

Soil Conservation Methods cont’d

Soil Conservation Methods cont’d

3. Gully Reclamation & Windbreaks cont’d

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

3. Windbreaks

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

Soil Conservation Methods cont’d

4. Maintaining & Restoring Soil Fertility

Involves the use of:

1. organic fertilizers

2. crop rotation (may add

nutrients to

soil)

Alternatives to Pesticides1. Agricultural Methods:• tillage of land – to expose pests• proper timing of planting, fertilizing and irrigating• Crop rotation• plant rows of hedges or trees (habitat for natural predators to pest)

2. Genetic Control• breed crops and animals resistant to pests

• sterilize members of the pest population

                                                                                          

Alternatives to Pesticides cont’d

3. Natural Enemies (Biological Control)

• predators, parasites & pathogens can be encouraged or

imported to regulate pest populations

4. Use of hormones and pheromones

• Pheromone – chemical sex attractant that may be used in

traps

• Hormones – manipulated and released at certain times can

disrupt growth and development of pest

Alternatives to Pesticides cont’d

5. Quarantine

• restriction of the importation of exotic plant and animal

material that might harbour pests

INTEGRATED PEST MANAGEMENT (IPM)

• combines use of biological, cultural and chemical

control

• non-chemical controls used as far as possible; pesticides

used sparingly when other methods fail

Organic Fertilizer

Organic Fertilizer

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

3 Basic Types of Organic Fertilizer

- Animal Manure

- Green Manure

- Compost

Organic Fertilizer 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 Fertilizer 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, 1963

- 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 Utilization Act

• Country Fires Act

• The Mining Act

• Wildlife Protection Act