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  1. 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.

  2. Lecture 7 Land and Human Populations

  3. In the beginning: • There were natural ecosystems • The land was covered with forests • There were many species • There was no waste

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

  5. 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

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

  7. 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

  8. Early impact was minimal: • Population levels were low • Activities were for survival • There was respect for nature

  9. Competing uses for land: • Agriculture (37%) • Forests (31%; 3,402 km2) • Housing and Industry (5%) • Mixed Use (27%) • Total Area (10,964 km2)

  10. Competing uses for land cont’d: • Bauxite • Roads • Waste Disposal • Burial Ground

  11. 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

  12. 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

  13. Waste Disposal - landfills take up space - deprive future generations of valuable resources

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

  15. 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

  16. 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

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

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

  19. Subsistence Agriculture • production for family sustenance • still practiced in many parts of the world

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

  21. Impact of Slash & Burn Cultivation - also called ShiftingCultivation - plots abandoned after 2-5 years due to loss of soil fertility

  22. Innovations: • The diesel engine • Motor vehicles • Medicines • Pesticides • Fertilizers

  23. These led to: • The Industrial revolution • The Green Revolution

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

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

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

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

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

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

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

  31. 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

  32. 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

  33. 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

  34. 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

  35. 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

  36. Disruption of Habitat - over-fertilization of rivers caused by runoff of nitrates and phosphates

  37. EFFECTS OF EUTROPHICATION

  38. 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

  39. 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

  40. 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

  41. 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

  42. Other Impacts of Agriculture on the Environment Desertification - process whereby agricultural productivity of land falls by 10% - conversion of rangeland to desert-like land

  43. Sustainable Agriculture • Crops grown in harmony with the environment • Health of humans and livestock important • Environment important • Workers important • eg. Organic agriculture, biodynamic agriculture

  44. 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

  45. 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

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

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

  48. 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