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L6 - Summary Questions. 1.How is population growth rate calculated? Differentiate between immigration and emigration. List four factors affecting growth rate. Which is the main factor that reduces fertility rate? List four effects of urbanisation. Lecture 7. Land and Human Populations. - PowerPoint PPT Presentation
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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.
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
Competing uses for land:
• Agriculture (37%)
• Forests (31%; 3,402 km2)
• Housing and
Industry (5%)
• Mixed Use (27%)
• Total Area (10,964 km2)
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
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
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
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 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
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 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.
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