Human Impact on the Biosphere

1. Human Impact on the Biosphere Intro to Environmental Science

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 (LDCs), per capita resource use is fairly low but growing, as is population size • In developed countries (MDCs), population growth has slowed but per capita resource use is very high

4. Pollutants • Substances with which an ecosystem has had no prior evolutionary experience or adaptive mechanisms. • Depends on concentration, location, and timing.

5. Air Pollutants • Carbon oxides • Sulfur oxides • Nitrogen oxides • Volatile organic compounds(VOCs) • Photochemical oxidants • Suspended particles

6. Industrial 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 • Brown-air to orange smog • Forms when sunlight interacts with primary release chemicals • Nitrogen oxides are major culprits • Hot days contribute to formation as does thermal inversion

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 • 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

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 fully 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 (non-arable) • 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

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 • Possible amplification of the greenhouse effect

18. Regions of Deforestation • Rates of forest loss are greatest in Brazil, Indonesia, Mexico, and Columbia • Highly mechanized logging is proceeding in temperate forests of the United States and Canada

19. Reversing Deforestation • Coalition of groups dedicated to saving Brazil’s remaining forests • Smokeless wood stoves have saved firewood in India • Kenyan women have planted millions of trees

20. 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

21. Desertification • Conversion of large tracts of grassland to desertlike conditions • Conversions of cropland that result in more than 10 percent decline in productivity

22. The Dust Bowl • Occurred in the 1930s in the Great Plains • Inappropriate cultivation techniques, overgrazing and prolonged drought left the ground bare • 1934 winds produced dust storms that stripped about 9 million acres of topsoil

23. Ongoing Desertification • Sahel 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

24. 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

25. Negative Effects of Irrigation • Salinization, mineral buildup in soil • Elevation of the water table and waterlogging • Depletion of aquifers

26. Ogallala Aquifer • Extends from southern South Dakota to central Texas • Major source of water for drinking and irrigation • Overdrafts have depleted half the water from this nonrenewable source

27. Aquifer Problems

28. Water Pollutants • Sewage • Animal wastes • Fertilizers • Pesticides • Industrial chemicals • Radioactive material • Excess heat (thermal pollution)

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

30. 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

31. 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)

32. Fossil Fuels • Coal, oil, natural gas • Main energy source of developed countries • Burning of fossil fuels contributes to global warming

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

34. Coal • Extensive reserves exist • Mining is very destructive • Burning coal releases sulfur dioxides that cause acid deposition

35. 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 radioactive wastes • Potential for meltdown

36. 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

37. 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

38. 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

39. 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

40. Changes in the World of Life • Adaptations of species have changed the environment • Photosynthetic organisms that arose during the Proterozoic altered the atmosphere by adding oxygen • Change is natural

41. Humans and Change Unlike previous species, human have the capacity to observe and make decisions about the changes they bring about

42. The Big Picture Environment Economics Socio-politics

43. References • Modified from presentation of Prentice Hall Publishers, 2002