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Human Impacts on the Biosphere

Human Impacts on the Biosphere. Chapters 55 & 56. Eutrophication. Human activities have increased the supply of nitrogen compounds available to primary producers, mostly through commercial fertilizers. Removal of vegetation removes nutrients from soil.

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Human Impacts on the Biosphere

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  1. Human Impacts on the Biosphere Chapters 55 & 56

  2. Eutrophication • Human activities have increased the supply of nitrogen compounds available to primary producers, mostly through commercial fertilizers. • Removal of vegetation removes nutrients from soil. • Agricultural runoff results in excess nutrients in aquatic systems, causing oxygen depletion, then death of organisms. • Lake Erie; Lake Washington

  3. Acid Precipitation • Burning of fossil fuels releases gases into the atmosphere which form acidic solutions when combined with water vapor. • Sulfur oxides – sulfuric acid • Nitrogen oxides – nitric acid • Carbon dioxide – carbonic acid. • pH decreases in lakes, rivers, etc, as well as soil, leaching nutrients, diminishing productivity, and harming organisms.

  4. Toxins in the Environment • Biological magnification – toxic substances become more concentrated higher up the food chain. • Top-level consumers are most affected. • Many toxins persist in the environment for long periods of time. • DDT, mercury, PCBs (polychlorinated biphenyls). • Video

  5. Greenhouse Gases • Naturally-occurring greenhouse gases include methane, carbon dioxide, and water vapor. • Human activities produce more of these, plus nitrous oxides and CFCs. • Intensification of greenhouse effect is referred to as “global warming” and may be contributing to climate change. • Snow/ice melt, shifting plant/animal communities, extreme weather patterns.

  6. Ozone Depletion • Ozone (O3) in the stratosphere blocks most UV radiation from reaching the earth’s surface. • Accumulation of CFCs has resulted in thinning of the ozone layer. • Animation • Montreal Protocol (1987) banned manufacture and use of CFCs. • Some developing countries still use CFCs; CFCs persist in the atmosphere for decades.

  7. Threats to Biodiversity • Biological diversity includes species diversity, genetic diversity, and ecosystem diversity … all are resources for humans. • #1 Habitat loss and fragmentation (managing protected areas) • #2 Introduced species (control of transplanted species, restoration) • #3 Overexploitation (establish population minimums, conservation) • ALIENS!

  8. New Species and Diseases • Introduced species which are pathogens can have drastic effects on a population. • Native species can have little natural immunity; acquired immunity and the evolution of resistance takes time. • Dutch Elm Disease: Fungal (native to Asia) infection transmitted tree-to-tree or by bark beetles; hit the U.S. by 1930 from a shipment of logs from Europe. • Small Pox: Virus probably from China; Europe, then Americas; ~30% mortality rate in Asia and Europe; 40 to 100% mortality for Native American tribes. Video

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