Polar bears and walruses at risk as Arctic ice melts

Polar bear mothers will have a harder time carrying cubs to term as Arctic sea ice dwindles, a new study said, and the U.S. government recognized that Pacific walruses need protection in their melting icy habitat.

Arctic ice reached the third-lowest level ever recorded in 2010, and was at record low levels in January. Because the Arctic is a major weather-maker for much of the Northern Hemisphere, these changes are being blamed for severe storms in some of the world's most densely populated areas.

Polar bears depend on sea ice as platforms for hunting the fatty seals that are central to their diet, and the loss of Arctic ice could push down population numbers for the species, a study in the journal Nature Communications said on Tuesday.

The study predicted that if Spring sea ice breaks up a month earlier than usual, 40 percent to 73 percent of pregnant polar bears could fail to bring their cubs to term; if sea ice breaks up two months earlier than usual, that projection rises to 55 percent to 100 percent.

Sea ice loss caused by climate change results in smaller polar bear litters, the study said. If the trend continues, "failure to reproduce could jeopardize population viability," the study's authors wrote. The study was supported by a diverse group of environmental, scientific and academic organizations.

Polar bears are listed as threatened under the U.S. Endangered Species Act, and their icy habitat has been designated as critical, which offers further protections.

However, conservationists fear that continued global warming could accelerate the loss of Arctic sea ice, putting polar bears under increased environmental pressure.

WALRUSES ON THE SHORE

"This new analysis backs the concerns of both scientists and indigenous peoples about the impacts of warming on Arctic species," Geoff York of WWF's Arctic program said in a statement. "Species everywhere are feeling the heat, but none more extreme than polar bears and other Arctic species."

Pacific walruses, which range along the Alaskan coast among other areas, use sea ice as platforms to give birth, nurse their young and elude predators. On Tuesday the U.S. Fish and Wildlife Service determined that these animals warrant protection under the Endangered Species Act.

"The Service has concluded that loss of sea ice -- with the resulting changes to walrus distribution and life history patterns this loss entails -- will lead to a population decline and is a threat to Pacific walrus in the foreseeable future," the agency said in a statement.

Last year, the loss of Arctic sea ice caused an estimated 10,000 to 20,000 Pacific walruses to come up on land, according to U.S. Geological Survey observations.

But because of a "need to address other higher priority species," the service said Pacific walruses will be listed as candidates for protection, but not protection itself. Their condition will be reviewed annually.

Pacific walruses are already protected under the Marine Mammal Protection Act, which the Fish and Wildlife Service said offers similar safeguards to the Endangered Species Act. This means Pacific walruses and walrus products can't be harvested, imported, exported or be part of interstate commerce.

New research about the future of Arctic ice indicates that even an ice-free summer would not necessarily create a "tipping point" that would doom the Arctic sea ice cap.

Writing in the journal Geophysical Research Letters, researchers said the Arctic Ocean would likely recover quickly from such a warm summer, whether the total melt occurred in 2000 or in 2060, when global mean temperature is projected to be 3.6 degrees F (2 degrees C) warmer.