Filtering Widlife

Filtering Widlife - PERSPECTIVES ECOLOGY Filtering Wildlife...

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23 JULY 2010 VOL 329 SCIENCE www.sciencemag.org 402 PERSPECTIVES ECOLOGY Justin S. Brashares CREDIT: ADAPTED BY P. HUEY/ SCIENCE “Extinction fi lters” help visualize complex threats faced by wildlife in protected areas. ±O n 24 April 1903, U.S. President Theodore Roosevelt stood before a crowd outside Gardiner, Mon- tana, and dedicated the world’s rst national park as a place where “the wild creatures of the Park are scrupulously preserved. ..” ( 1 ). Thirty years later, scientists reported the local extinction of Yellowstone National Park’s “white-tailed deer, cougar, lynx, wolf, and possibly wolverine and fisher. ..” ( 2 , 3 ). More than 100,000 protected areas world- wide now follow in Yellowstone’s footsteps, both in their goal of preserving wildlife and in the dif- ficulties they face in achieving this goal. A growing literature highlights the diverse and com- plex threats faced by wildlife in protected areas, and the pressing need for better tools and moni- toring programs for predicting, understanding, and addressing wildlife declines. Protected areas are the undis- puted backbone of wildlife con- servation efforts on land and at sea. Analysts often use the pace and scale of their creation to assess global conservation strat- egies ( 4 ). Yet conservation biolo- gists have long warned that even well-managed protected areas will lose species over time, and of the risks of relying on such areas as reservoirs for nature ( 5 ). Recent research sug- gests that habitat protection reduces extinc- tion rates but also that extinctions occur reg- ularly in protected areas of both developing and developed nations and at rates faster than predicted by conservative models ( 6 , 7 ). Alarmingly, there appear to be few obvious patterns to these extinctions that might allow conservationists to predict and protect those species most likely to be at risk ( 7 10 ). At first glance, the causes of wildlife declines in a protected area may seem obvi- ous. Excessive hunting, for instance, effec- tively extirpated wolves, mountain lions, and other large carnivores from Yellowstone National Park ( 2 ). Modern extinctions in pro- tected areas, however, are seldom so easily attributed to one cause. Recent studies link them to an array of threats that vary, often unpredictably, across time and space ( 7 10 ). They range from global phenomena such as climate change and atmospheric pollution, to regional issues such as shifts in fi re regimes, disease dynamics, or invasive species, to more localized threats such as overharvest, habitat conversion, and the effects of isolation. These threats can interact both additively and syn- ergistically to create syndromes of extinc- tion that confound diagnosis and remedy ( 7 11 ). A fi nal layer of complexity is that each threat can have a unique impact that depends on an animal’s vulner- ability, as determined by life his- tory and other traits ( 8 ). “Extinction filters” pro-
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Filtering Widlife - PERSPECTIVES ECOLOGY Filtering Wildlife...

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