Charismatic bears on thin ice

For most people, the likelihood of climate change making a big difference in their lives still seems largely theoretical. But throw in the prospect that global warming may mean curtains for some of humankind's favorite other species – "charismatic megafauna," they're sometimes called – and the issue gains additional urgency.

The US Geological Survey (USGS) reports that two-thirds of the world's polar bears could disappear by mid-century as Arctic sea ice continues to melt due to unusually warm temperatures.

"The new findings paint a sobering picture ' reports National Geographic News. 'Our results have demonstrated that as the sea ice goes, so goes the polar bear," said Steven Amstrup, a USGS wildlife research biologist in Anchorage, Alaska, and leader of the polar bear studies. The rapid movement of sea ice could leave bears stranded in food-poor areas, or it might require them to make long and exhausting swims from food-rich areas back to the ice, Dr. Amstrup says.

This year has already broken the 2005 record for the lowest amount of Arctic sea ice ever recorded. In one week's time, reports ABC News, "an area of Arctic sea ice the size of Florida has melted away."

Says scientist Mark Serreze, a polar ice expert at the National Snow and Ice Data Center in Boulder, Colo.:

"If you had asked me a few years ago about how fast the Arctic would be ice free in summer, I would have said somewhere between about 2070 and the turn of the century.... My view has changed. I think that an ice-free Arctic as early as 2030 is not unreasonable."

The USGS study was ordered up by US Interior Secretary Dirk Kempthorne to help scientists and officials decide whether polar bears should be protected under the Endangered Species Act (ESA). The US Fish and Wildlife Service has proposed listing the bear as "threatened" under the ESA. That decision is to be made in January.

The news from the latest research is not encouraging, according to the USGS.

"Projected changes in future sea ice conditions, if realized, will result in loss of approximately 2/3rds of the world's current polar bear population by the mid 21st century."

The picture appears even worse than environmentalists had warned when they sued the federal government two years ago, forcing the endangered species review of polar bears by Interior Secretary Kempthorne. That's especially true in Alaska, where all the bears are expected to be lost, reports the Anchorage Daily News:

"Polar bears have been known to live as long as 30 years.... That means today's young bears may be part of the last generation in Alaska. While older bears will probably scrape along, scientists expect to see cubs and young adults die off and reproduction rates decline. Already, studies have reported shrinking weight and rising mortality of cubs. There have also been reports of polar bears drowning."

Among those who track ice patterns in the polar regions, there seems to be little doubt that climate-changing greenhouse gases are playing an important part in current trends, particularly since the world's oceans absorb much of the additional heat down to depths of several hundred feet. Dr. Serreze, the Arctic specialist at the US National Snow and Ice Data Center, told the British newspaper The Guardian:

"It seems that the Arctic is going to be a very different place within our lifetimes, and certainly within our children's lifetimes."

Sea ice usually melts in the Arctic summer and freezes again in the winter, the article says. But this year is different. "This summer we've got all this open water and added heat going into the ocean. That is going to make it much harder for the ice to grow back," Serreze told The Guardian. Wind and ocean circulation patterns can play a part in reducing sea ice, but the main culprit is man-made global warming, he says. "The rules are starting to change, and what's changing the rules is the input of greenhouse gases."

Meanwhile, scientists now suspect that global warming may have caused the population of gray whales in the Pacific to decline due to changing conditions in their feeding grounds, reports National Geographic News. It quotes Phillip Clapham, who works at the Alaska Fisheries Science Center, part of the National Oceanic and Atmospheric Administration's National Marine Mammal Laboratory in Seattle as saying:

"It's clear that future climate change will significantly impact the Arctic and sub-Arctic ecosystems on which gray whales and other species depend.... But quite how that colossal unintentional experiment comes out is anyone's guess."

Last year, National Geographic News reported that "The north Bering Sea, one of the world's richest feeding grounds ... is warming to the point where animals are being forced to adapt or suffer the consequences."

"Some animals, like gray whales, are moving farther north to follow the cold water. Meanwhile, pink salmon and pollock, fish typically found in the southeast Bering Sea, are moving into northern waters. Other animals of the north Bering Sea may not be adapting enough to survive. Bearded seals and walruses, which feast on ... bottom-dwellers, are struggling with a reduced food source."