Arctic melt threatens Polar bears

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If warming of the Arctic continues to erode sea ice, as predicted by many climate scientists, the iconic white carnivores will be driven ashore or onto increasingly smaller floes in their endless feast-or-famine hunt for seals.

Many animals will then sicken and starve. Whole polar bear populations will die.

The 40 members of the polar bear specialist group of the World Conservation Union are warning that the population of the Arctic’s top predator could deplete by 30 percent during the next 35 to 50 years and should now be rated as vulnerable on an international “red list” of threatened species.

“This is the first time that we’ve evaluated the plight of polar bears [with] respect to climate change, and we found that they were vulnerable to extinction,” said the group’s outgoing chairman, biologist Scott Schliebe, who oversees management of polar bears in Alaska for the U.S. Fish and Wildlife Service. “Polar bears don’t have a place to go if they lose the ice.”

During the past decades, sea ice has lost thickness, melted faster in spring and re-formed later in fall, according to the international Arctic Climate Impact Assessment. Vast stretches near Alaska have become ice-free during the past three summers, setting a record in 2003 and a near-record in 2004 for least coverage ever measured. The thick multiyear ice essential to polar bears has been shrinking 8 percent to 10 percent a decade.

Some climate models predict summer ice could disappear from the Arctic Ocean by the end of the century.

Polar bear experts say the loss of ice will devastate the seal-eating carnivores, thought to number up to 25,000 in 19 separate populations, including two off the coast of Arctic Alaska: the Chukchi Sea bears shared with Russia and the Beaufort Sea bears shared with Canada.

Believed to have evolved at least 250,000 years ago from brown bears, polar bears spend their lives stalking seals and an occasional beluga whale or walrus in a frozen wilderness of grinding floes. One or 2 pounds at birth, male bears can grow to more than a half-ton by maturity. The much smaller female hibernates when pregnant, digging out winter dens to nurture cubs.

They are curious and relentless hunters, with sharp teeth and short claws totally adapted to marine life. Despite a mythic reputation for ferociousness, they often act cautiously around other bears.

The bears cannot simply evolve back to living on land over a generation or two, Mr. Schliebe said, and will begin disappearing as ice cover shrinks.

Although the group named climate warming and the destruction of the ice habitat as the main threat to the species, it also cited poaching in Russia and threats by contaminants as other problems.

Source: Washington Times