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Human Impact on the Biosphere

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  1. Human Impact on the Biosphere Chapter 45

  2. Human Impacts • Humans are using energy and altering the environment at astonishing rates • We are altering natural processes before we even understand them

  3. Developing vs. Developed • In developing countries, per capita resource use is low but growing, as is population size • In developed countries, population growth has slowed but per capita resource use is already high

  4. Pollutants • Substances which have harmful effects on humans and the natural world • Substances with which an ecosystem has had no prior evolutionary experience • No adaptive mechanisms are in place to deal with them

  5. Air Pollutants • Carbon oxides burning fossil fuel • Sulfur oxides mostly from coal • Nitrogen oxides mostly from cars • Volatile organic compounds = unburned Hydocarbons • Photochemical oxidants = ozone • Suspended particles = smoke, soot

  6. Industrial (Gray) Smog • Gray-air smog • Forms over cities that burn large amounts of coal and heavy fuel oils; mainly in developing countries • Main components are sulfur oxides and suspended particles

  7. Photochemical smog • Reddishbrown-air smog • Forms when sunlight interacts with components from automobile exhaust • Nitrogen oxides are the main culprits • Hot days contribute to formation

  8. Thermal Inversion • Weather pattern in which a layer of cool, dense air is trapped beneath a layer of warm air cool air warm inversion air cool air

  9. Acid Deposition/Acid Rain • Caused by the release of sulfur and nitrogen oxides • Coal-burning power plants and motor vehicles are major sources

  10. South America Antarctica Ozone Thinning • In early spring and summer ozone layer over Antarctica thins • Seasonal loss of ozone is at highest level ever recorded • Lets in more UV radiation

  11. Effect of Ozone Thinning • Increased amount of UV radiation reaches Earth’s surface • UV damages DNA and negatively affects human health • UV also affects plants, lowers primary productivity

  12. Protecting the Ozone Layer • CFC production has been halted in developed countries, will be phased out in developing countries • Methyl bromide will be phased out • Even with bans it will take more than 50 years for ozone levels to recover

  13. Generating Garbage • Developed countries generate huge amounts of waste • Paper products account for half the total volume • Recycling can reduce pollutants, save energy, ease pressure on landfills

  14. Land Use • Almost 21 percent of Earth’s land is used for agriculture or grazing • About half the Earth’s land is unsuitable for such uses • Remainder could be used, but at a high ecological cost

  15. Green Revolutions • Improvements in crop production • Introduction of mechanized agriculture and practices requires inputs of pesticides, fertilizer, fossil fuel • Improving genetic character of crop plants can also improve yields • Sustainable? Not for much longer

  16. Deforestation • Removal of all trees from large tracts of land • 38 million acres logged each year • Wood is used for fuel, lumber • Land is cleared for grazing or crops

  17. Effects of Deforestation • Increased leaching and soil erosion • Increased flooding and sedimentation of downstream rivers • Regional precipitation declines = desertification • Amplification of the greenhouse effect

  18. Destroying Biodiversity • Tropical rainforests have the greatest variety of insects, most bird species • Some tropical forest species may prove valuable to humans • Our primate ancestors evolved in forests like the ones we are destroying

  19. Desertification • Conversion of large tracts of grassland to desertlike conditions usually by over grazing • Conversions of cropland that result in more than 10 percent decline in productivity

  20. The Dust Bowl • Occurred in the 1930s in the Great Plains • Farming marginal land prolonged drought left the ground bare • 1934 winds produced dust storms that stripped about 9 million acres of topsoil

  21. Ongoing Desertification • Sub-Sahar region of Africa is undergoing rapid desertification • Causes are overgrazing, overfarming, and prolonged drought • One solution may be to substitute native herbivores for imported cattle

  22. Water Use and Scarcity • Most of Earth’s water is too salty for human consumption • Desalinization is expensive and requires large energy inputs • Irrigation of crops is the main use of freshwater

  23. Aquifer Problems

  24. Water Pollutants • Sewage containing organic wastes become Oxygen Demanding Wastes • Fertilizers stimulate algal growth • Pesticides • Industrial chemicals • Radioactive material • Excess heat (thermal pollution)

  25. Wastewater Treatment • Primary treatment • Use of screens and settling tanks • Addition of chlorine to kill pathogens • Secondary treatment • Microbes break down organic matter (ODW) • Tertiary treatment removes additional toxic substances; rarely used

  26. Water Wars? • Per capita amount of freshwater available is decreasing • International conflicts over water use and quality have already occurred • Building dams or dumping pollutants effect countries downstream

  27. Energy Use • Only 10 percent of energy used in developed countries is from renewable sources • Less developed countries rely more heavily on renewable sources (primary biomass like wood)

  28. Fossil Fuels • Coal, oil, natural gas • Main energy source of developed countries • Burning of fossil fuels contributes to global warming, air pollution, & acid rain

  29. Oil • Reserves are declining • Many reserves are in ecologically fragile wilderness areas • Environmental costs of extracting and transporting reserves from such areas are high

  30. Coal • Good news, there is a lot of it. Bad news, we have to use it • Mining is very destructive • Burning coal releases sulfur dioxides that cause acid deposition. Sulfur can be removed (at a cost)

  31. Nuclear Energy • Used extensively in some energy-poor developed countries • Little support in the United States • Emits fewer air pollutants than burning coal, but creates dangerous radioactive wastes • Potential for meltdown

  32. Chernobyl Accident - 1986 • Core meltdown at a nuclear power plant in the Ukraine • 31 immediate deaths, radiation sickness and death for others • Cloud of radiation spread by winds across Europe • Long-term health impacts downwind

  33. Solar-Hydrogen Energy • Photovoltaic cells use sunlight energy to split water • Hydrogen gas produced in this way can be used as fuel or to generate electricity • Clean, renewable technology

  34. Wind Energy • An indirect use of solar energy • Wind farms are arrays of turbines • Can supplement needs of some regions but is not dependable enough on it own

  35. Fusion • Energy is released when atomic nuclei fuse • This process produces solar energy • Attempts to mimic this process on Earth require use of lasers, magnetic fields • Not yet a commercially viable energy source

  36. Humans and Change • Unlike previous species, human have the capacity to observe and make decisions about the changes they bring about • Hopefully we will in time!