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Land and Human Populations

Land and Human Populations. Competing uses for land :. Forests (31%) Agriculture (37%) Housing and Industry (5%) Roads Waste Disposal. …Watersheds were forested. Watersheds are also called drainage basins or catchment areas

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Land and Human Populations

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  1. Land and Human Populations

  2. Competing uses for land: • Forests (31%) • Agriculture (37%) • Housing and Industry (5%) • Roads • Waste Disposal

  3. …Watersheds were forested • Watersheds are also called drainage basins or catchment areas • They are areas of land that drain into bodies of surface water

  4. Functions of Watersheds • Forested watersheds act as giant sponges increasing infiltration • They release water slowly moderating flooding and maintaining stream flows in dry periods

  5. Functions of Watersheds • They control soil erosion improving water • quality • They are habitats for many species • They regulate rainfall on a small scale

  6. Rainfall Impact and Trees Trees break the impact of rainfall on the soil thus reducing soil erosion.

  7. Jamaican Watersheds • >1/3 have deteriorated Causes of Jamaican Watershed Destruction 1. Unsuitable hillside agricultural practices 2. Illegal settlements on hillside lands

  8. Causes of Jamaican Watershed Destructioncont’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

  9. Effects of Watershed Destruction • Massive soil loss through soil erosion • Siltation of drains and rivers • Destructive flooding downstream • Water pollution • Reduced water availability and quality • Loss of habitat for flora and fauna

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

  11. Three Main Types of Agriculture 1. Subsistence • Industrialised 3. Sustainable

  12. Subsistence Agriculturecont’d • Features of Low Input / Subsistence Agriculture: • Human Labour • Slash and Burn • Shifting Cultivation • Fallow Periods • Animal Manure • Mixed Cropping

  13. Industrialised Agriculture • also called modern or advanced agriculture • one crop or animal for sale • use large amounts of : a) fossil fuel energy b) water

  14. Industrialised Agriculturecont’d • Features of High Input/Conventional Agriculture: • Mechanisation • Monocropping • Synthetic Pesticides • Synthetic Fertilizers • Genetic Engineering • Irrigation

  15. Mechanisation • causes land degradation through soil compaction • exacerbates soil erosion • causes decline in soil fertility • erosion damage causes decreased water quality

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

  17. Soil Erosioncont’d Soil Erosion is caused by: • Farming • Logging • Building • Overgrazing • Four-wheeling

  18. Soil Erosioncont’d The 3 Main Effects of Soil Erosion are: • Loss of topsoil • Reduced productivity • Surface water pollution

  19. 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

  20. 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

  21. 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

  22. 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

  23. 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

  24. 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.

  25. Impacts of Agriculture on the Environmentcont’d 1. Chemical Damage - pollution of rivers & streams from pesticide runoff - nitrates & pesticides in drinking water, food & air

  26. Impacts of Agriculture on the Environmentcont’d 2. Disruption of Habitat - over-fertilization of rivers caused by runoff of nitrates and phosphates

  27. Impacts of Agriculture on the Environmentcont’d 3. Loss of Biodiversity - reduction in nutrient recycling soil organisms - loss of plant genetic diversity - endangerment & extinction of wildlife

  28. Impacts of Agriculture on the Environmentcont’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 & ruins the land

  29. Impacts of Agriculture on the Environmentcont’d 5. Desertification - process whereby agricultural productivity of land falls by 10% - conversion of rangeland to desert-like land

  30. Impacts of Agriculture on the Environmentcont’d 6. Slash & Burn Cultivation - also called ShiftingCultivation - plots abandoned after 2-5 years due to loss of soil fertility

  31. Impacts of Agriculture on the Environmentcont’d 7. Overgrazing - destruction of vegetation when too many grazing animals feed too long & exceed the carrying capacity of a rangeland area

  32. Sustainable Agriculture • Crops grown in harmony with the environment • Health of humans and livestock important • Environment important • Workers important • e.g. Organic agriculture

  33. Sustainable Agriculture Cont’d • Includes the use of: • Companion cropping/mixed farming • Soil conservation • Addition of organic matter • Use of alternatives to pesticides

  34. 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

  35. Soil Conservation Methodscont’d Major Methods Include: • Conservation tillage • Contour farming, Terracing, Strip cropping, & Alley cropping • Gully reclamation & Windbreaks • Land-Use Classification & Control • Maintaining & Restoring soil fertility

  36. Soil Conservation Methodscont’d • Conservation Tillage - crop cultivation with little or no soil disturbance ▪ Minimum Tillage ▪ No-till Farming

  37. Soil Conservation Methodscont’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

  38. Soil Conservation Methodscont’d 2. Contour Farming, Terracing, Strip Cropping & Alley Cropping cont’d ▪ Terracing - used on steeper slopes

  39. Soil Conservation Methodscont’d 2. Contour Farming, Terracing, Strip Cropping & Alley Cropping cont’d ▪ Alley Cropping (Agroforestry) - planting crops with rows of trees on each side

  40. Soil Conservation Methodscont’d 3. Gully Reclamation & Windbreaks ▪ Gully Reclamation

  41. Soil Conservation Methodscont’d 3. Gully Reclamation & Windbreaks cont’d ▪ Windbreaks (Shelterbelts) - row of trees planted to block wind flow

  42. Soil Conservation Methodscont’d 4. Land Use Classification System - describes different categories of land that are suitable and unsuitable for cultivation

  43. Soil Conservation Methodscont’d 5. Maintaining & Restoring Soil Fertility Involves the use of: 1. organic fertilizers 2. crop rotation

  44. Alternatives to Pesticides • Cultivation Practices - mow weeds - rotate crops - plant rows of hedges or trees • Resistant Varieties - genetically resistant to certain pest insects, fungi and diseases

  45. Alternatives to Pesticidescont’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 sterilized, then released into population.

  46. Alternatives to Pesticidescont’d • 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

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