Human Impact on the Biosphere

1. Human Impact on the Biosphere

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 high but growing, as is population size • In developed countries, population growth has slowed but per capita resource use is already high

4. Pollutants • 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 • Sulfur oxides • Nitrogen oxides • Volatile organic compounds • Photochemical oxidants • Suspended particles

6. Chemistry 101 • Acid anhydrides: oxides of nonmetals • CO2, NO2 and SO3 • These react with water to form oxyacids. • CO2 + H2O ---> H2CO3 (carbonic acid) • HNO3 and H2SO4 are also formed in the atmosphere

7. Acid Rain and Architecture • On campus we have some architectural damage attributable to acid rain. • The limestone lentils and pillars on the older building are dissolving away! • H2SO4(aq) + CaCO3(s) H2O(l) + CO2(g) +CaSO4(aq)

8. 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

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

10. 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

11. Cities Are Often Plagued with Thermal Inversions

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

13. 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

14. 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

15. Ozone in Earth’s Atmoshere

16. Ozone Concentration from 1962 to 1996 http://www.igf.edu.pl/igf/atmosphere.htm

17. Recipe for Ozone Loss • “The polar winter leads to the formation of the polar vortex which isolates the air within it. • Cold temperatures form inside the vortex; cold enough for the formation of Polar Stratospheric Clouds (PSCs). As the vortex air is isolated, the cold temperatures and the PSCs persist. • Once the PSCs form, heterogeneous reactions take place and convert the inactive chlorine and bromine reservoirs to more active forms of chlorine and bromine. • No ozone loss occurs until sunlight returns to the air inside the polar vortex and allows the production of active chlorine and initiates the catalytic ozone destruction cycles. Ozone loss is rapid. The ozone hole currently covers a geographic region a little bigger than Antarctica and extends nearly 10km in altitude in the lower stratosphere” http://www.atm.ch.cam.ac.uk/tour/part3.html

18. 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

19. 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

20. Garbage Barge Solution

21. Landfills

22. 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

23. 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

24. Data From the UN

25. INDIA REACHING 1 BILLION ON AUGUST 15: NO CELEBRATION PLANNEDLester R. Brown and Brian Halweil • Falling water tables are now also threatening India's food production. • The International Water Management Institute (IWMI) estimates that withdrawals of underground water are double the rate of aquifer recharge. • As a result, water tables are falling almost everywhere. http://www.worldwatch.org/node/1656

26. Aquifer Depletion http://www.uwgb.edu/dutchs/EarthSC202Notes/Grndh2o.htm

27. 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

28. Clear Cutting of Forests

29. Effects of Deforestation • Increased leaching and soil erosion • Increased flooding and sedimentation of downstream rivers • Regional precipitation declines • Possible amplification of the greenhouse effect

31. 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

32. “A heavy duty tree chopper for cutting down trees in a logging operation.”

33. Rainforests

34. Forests Burning

35. 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

36. NAIROBI (AFP) Feb 23, 2005 NAIROBI (AFP) Feb 23, 2005“Kenyan Nobel peace laureate Wangari Maathai on Wednesday urged developing nations to help fight global warming and support the Kyoto Protocol on climate change by joining her tree-planting campaign.”

37. 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

38. Primates Many primate species are threaten or endangered.

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

40. Global Desertification Vulnerability

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

43. Caption: "Dust Over Texas." Huge boiling masses of dust that blocked out the sun were common sights in Texas during the Dust Bowl years. In: "To Hold This Soil", Russell Lord, 1938. Miscellaneous Publication No. 321, U.S. Department of Agriculture.

44. Human Tragedy

45. 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

46. Linear dunes of the Sahara Desert encroach on Nouakchott, the capital of Mauritania. The dunes border a mosque at left (photograph by Georg Gerster). http://pubs.usgs.gov/gip/deserts/desertification/

47. 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

48. Mean Annual Precipitation

49. Water Distribution

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