BilimarT

Tuesday, Feb. 12, 2008 By BRYAN WALSH - www.time.com

King penguins are supposed to be a wildlife success story. The flightless Antarctic bird — the second-biggest penguin after its movie-star emperor cousin — was hunted into near-extinction by sailors in the 19th century, who used their fat as cooking oil. When the slaughter ended — penguin fat no longer being the preferred way to simmer your cruise dinner — the penguin bounced back, and today numbers about 2 million. This is a healthy, robust species that sits near the top of the complex Antarctic food web.

They may not stay that way much longer. A new report by French scientists in the Proceedings of the Natural Academy of Sciences finds that king penguins could be wiped out over the coming decades due to global warming. Led by Yvon Le Maho, a physiologist at French National Center for Scientific Research, the team of researchers followed 456 adult birds with radio transponders implanted beneath their skin. Over an eight-year period, the researchers correlated survival rate to changes in sea surface temperatures, and found that in warm years, penguin chicks were less likely to survive the lean months of winter, because there wasn’t sufficient fish to feed them. (Warmer temperatures seem to lower fish populations in the Southern Ocean, off Antarctica.) Adult survival rates dropped as well in warmer years. Ultimately, the scientists report that a 0.47 degree F increase in the temperature of the Southern Ocean — considerably below current forecasts for the next several decades — would reduce penguin numbers by 9%, enough to touch off a population collapse. “Our findings suggest that king penguin populations are at heavy extinction risk under the current global warming predictions,” the study’s authors wrote.

That’s bad news for the penguins, and worse news for the rest of Antarctic wildlife. Sitting near the top of the food chain, the king penguins are useful markers for the health of the rest of the Antarctic ecosystem. If global warming means they’re not getting enough food, the conditions below the penguins could be even worse. Temperature rise due to climate change is occurring quicker at the poles than the rest of the planet — on the Antarctic Peninsula, temperatures have risen five times faster than the global average over the past 50 years. Even if we can manage to slow the growth in carbon emissions, the poles will likely continue to warm. Though the species that have evolved to survive in harsh Antarctic conditions are necessarily tough, they’re also delicate. They’re built for the snow and ice — change those conditions, and you take away their habitat and their food supply. Extinction comes next, and nothing can stop it.

The situation is no better in the Arctic north, where studies predict that polar bear populations will rapidly shrink over the coming decades, thanks again to warming. Environmentalists are pressing the U.S. Fish and Wildlife Service to declare the polar bear threatened, which would make it the first species to be recognized as endangered specifically because of climate change. The government recently failed to meet a self-imposed deadline to make the decision by Feb. 9, and the fate of the polar bear remains unclear. But if we fail to slow down the rate of warming, the polar regions as we know them will no longer exist — and possibly, neither will many of the species who live there now.

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Biyoetiketler: Nature, Science, Warming

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