Endangered Species 2011 - Endangered species Biodiversity...

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1 Biodiversity 3: Endangered species Endangered species Estimating risk of extinction Major causes of threat Protecting endangered species (Endangered Species Act) Passenger Pigeon Highly social birds Nested in forest colonies Abandoned chicks after 2 weeks “ The air was literally filled with Pigeons; the light of noon-day was obscured as by an eclipse, the dung fell in spots, not unlike melting flakes of snow; and the continued buzz of wings had a tendency to lull my senses to repose." - James J. Audubon 1813 Hunted to extinction • 1914: 1 bird left in Cincinnati Zoo • Uncontrolled hunting • 1855: 18,000 / day • Population collapsed in late 1800s “Martha” Why didn’t pigeons recover? • Breeding patterns required large social groups (predator defense) • Forest clearing (lack of nesting and feeding sites) Hunting drove pigeons close to extinction, but habitat loss and breakdown of social structure finished them off
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2 Ivory-billed woodpecker Video 1: ABC News Ivory Billed Rediscovered Vertebrate extinctions since 1600 Birds 139 9,956 1 Reptiles 23 1,385 2 Amphibians 35 5,915 1 Modern extinction rates are 10x higher than ‘background’ rates Assessing Extinction Risk www.redlist.org Quantifying extinction risk Lande and Mace 1991 Critically Endangered Endangered Vulnerable Low Risk Threatened with extinction… in 2007 Amphibians Mammals Threatened with extinction… in 2010 Type Number Threat’d Total N % Threat’d Mammals 1,130 5,490 21 Birds 1,240 10,027 12 Reptiles 467 1,672 28 Amphibians 1,895 6,285 30 ¼ of all vertebrates are threatened with extinction
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3 Log (Island area in km 2 ) Log (# species on island) Extinction rates and species- area curves Biodiversity increases with island / habitat size Birds of Figi Islands Species Area Curves log(area) Log(S) = C+ z log(A) A mathematical relationship to describe how species number depends on the amount of available habitat Estimating extinction rates Assume z = 0.35
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This note was uploaded on 10/04/2011 for the course ECOL 1000 taught by Professor Altizer during the Fall '08 term at University of Georgia Athens.

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Endangered Species 2011 - Endangered species Biodiversity...

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