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12_ Outline Human Impacts on Ecosystems

12_ Outline Human Impacts on Ecosystems - BSCI 106 Dr Sara...

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BSCI 106 Fall 2008, p. 1 Dr. Sara Via Human Impacts on Ecosystems We’ve discussed how humans alter nutrient cycles * N cycle: synthetic fertilizer, NO and NO 2 from combustion of fuel * P cycle: fertilizer and detergents * C cycle: CO 2 from combustion acid rain: combustion products water cycle: diversion of rivers, water Loss of productivity What are we doing about it? EPA cap and trade program for SO x Very successful! Cost much less than expected The Water Cycle– human impacts Billions of gallons removed from deep aquifers every day. Can they refill at the same rate? High Plains Aquifer- Kansas Water cycle– Logging *clearing forests increases runoff, soils may dry and compact *temperature rises as evaporative cooling from plant water loss is reduced * higher temperature reduces rainfall The N cycle & acid rain!
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BSCI 106 Fall 2008, p. 2 Dr. Sara Via Water cycle– human impacts Diversion of water from rivers to cities: * drying of rivers, * lowering of water table, * salination Do we REALLY need those golf courses and green lawns in the deserts of Arizona & southern California?? Human Impacts on Ecosystems Habitat destruction - tropical forests, urbanization Overfishing - cod, bluefin tuna Where are global rainforests going? 1. Logging - often only large trees are taken, but rest of tropical forest is fragile and taking big trees ruins it - clearcutting - tropical forests, old growth forest in Pacific NW of US - destroys water and nutrient balance - increases runoff - silts up streams and rivers - in tropics, clearcuts can become deserts 1. Logging - lumber from Pacific NW sold to Japan for pulp, turned into disposable diapers…. . - tropical lumber often made into inexpensive furniture (beware…) - OR, sold at high price for Brazilian cherry decks, hardwood floors, etc. - In Brazil, Congo, logging often done illegally, against wishes of the indigenous peoples - World Bank recently funded a plan to clear an area the size of France in Africa (who benefits?) - 2. Agriculture – - Clearing by subsistance farmers (many dispossessed,
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12_ Outline Human Impacts on Ecosystems - BSCI 106 Dr Sara...

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