Ecological principles 1 2011

Ecological principles 1 2011 - 9/2/2011 1 Ecological...

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Unformatted text preview: 9/2/2011 1 Ecological principles 1: Keystone predators, food webs and energy flows Yellowstone National Park First and oldest National Park Est in 1870s Hot springs, geysers, geology Animals of Yellowstone 9/2/2011 2 Wolves: extirpated in early 1900s Elk and coyotes increased Vegetation declined What happens when we add a top predator back into an ecosystem? Yellowstone food chain +- + 9/2/2011 3 Observational approach No wolves Wolves Compare tree density with vs. without presence of wolves Trees per km 2 Wolves No Wolves Observational data show trends Does not tell us about the mechanism (causation) Observational data show trends Does not tell us about the mechanism (causation) Experimental approach Control a variable and observe the effects Could introduce wolves and record changes that follow Lets go to Yellowstone! Video 1: NBC News Wolf reintroduction Video 1: NBC News Wolf reintroduction Wolf reintroduced: 1995-96 From 66 wolves (in YNP and Idaho) Now: > 300 in Greater Yellowstone area > 1000 in total 9/2/2011 4 Effects of wolves on ecosystem Wolves Elk Woody trees Changes in riparian vegetation By 2008, elk declined by more than half 100 wolves 10,000 fewer elk Elk are on the run!...
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Ecological principles 1 2011 - 9/2/2011 1 Ecological...

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