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Marine Life
Sea Lubbers

Norbert Rosing/National Geographic Stock

An observer flying over Point Lay, Alaska, this past September might have noticed a mass of sausagelike lumps packed densely along the shore: at least 10,000 Pacific walruses. Last year was the third since 2007 that such major exoduses onto land have occurred in the United States. It probably won’t be the last. The Arctic summer sea ice that the subspecies relies on as a resting platform is declining—and expected to disappear entirely by 2030—largely because of global warming.

The walruses’ movement to land is but one of the latest signs of the threat that warmer temperatures pose to the far north. “[They’re] just the tip of the iceberg,” says University of Virginia researcher G. Carleton Ray, who has studied the animals for more than 50 years. Shifts in sea ice are already altering other species’ behavior; some hungry polar bears, for example, have resorted to cannibalism. Such changes can cause “a cascade of reactions that ripple through the Arctic ecosystem,” says Ray (see “S.O.S.,” November-December 2007).

Pacific walruses winter in the Bering Sea’s shallow waters, where they breed. Come spring, most males stay put while mothers and calves follow retreating ice north into the Chukchi Sea. During summer they forage for benthic organisms, such as clams, snails, and worms, and congregate by the hundreds on ice floes to rest. But for six of the past eight years the Chukchi has had, in effect, no summer ice—a condition that had occurred only once in the prior 26 years. Winter ice is also starting to form later than ever before. As a result, the ice season is shortening at both ends.

Without sea ice, mother walruses and calves risk exhaustion and separation in the water and lumber onto land, where a threat (say, a polar bear) can convert a super-sized herd into a deadly stampede. “The little guys can get crushed,” says Anthony Fischbach, a U.S. Geological Survey wildlife biologist. Landlocked walrus hordes also compete for nearby food.

USGS researchers are tracking the mammals with radio tags to gather data that will help identify walrus-sensitive areas for fishermen and energy companies hoping to exploit ice-free waters. In February, however, walrus conservationists suffered a blow when the U.S. Fish and Wildlife Service decided that listing the animal under the Endangered Species Act was “warranted” but “precluded” by species of even higher concern. “That, in our view, is a black hole for the Pacific walrus,” says Shaye Wolf, climate science director at the Center for Biological Diversity. “The FWS is acknowledging that it’s at risk, but it’s withholding the very protections that can help it survive.”—Julie Leibach
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