Polar bears in danger from melting sea ice

Wednesday, February 14, 2007

By Melanie Stein

Speaking to a packed house of inquisitive Jacksonites last week at the National Museum of Wildlife Art, Dr. Steve Amstrup, the leading polar bear researcher in the U.S., painted a desperate picture for the Great White Bear as Arctic sea ice diminishes in the wake of global climate change.

Amstrup — who has conducted research, primarily in the Beaufort Sea region off Alaska for 25 years, and currently serves as research wildlife biologist with the U.S. Geological Survey at the Alaska Science Center — showed slides highlighting shifts in annual sea ice cover in the Arctic region since 1979.

Sea ice scientists have noted a 9 percent per decade decline in perennial sea ice for the last three decades in a row, Amstrup said. This translates into a loss of about 2 million square kilometers, due to warmer air and water temperatures and shifts in ocean circulation patterns.

Changes in sea ice coverage are significant for polar bears, as their livelihood depends to it. Polar bears are the largest, non-aquatic mammal and survive almost entirely by hunting ringed and bearded seals on the ice. Some bears also dig dens in snowdrifts on the ice where they have their cubs in the fall. Although bears are adept swimmers and can swim up to 150 miles, the ice is their true home.

“Polar bears are the sentinel species for climate change,” Amstrup said. They are the high predator in the Arctic food web, and dramatic changes to their population could affect other animals, like seals or Arctic foxes. “Arctic foxes are scavengers of polar bear kills,” Amstrup explained. “It’s reasonable to think there won’t be as much food” for foxes if polar bear populations decline.

In addition to decreased sea ice coverage, sea ice is breaking up and drifting into the North Atlantic earlier each year, forcing polar bears onto land, where they are less adept hunters and are often food-deprived.

“On average polar bears make a kill every four to five days and are well adapted to a ‘feast and famine’ regimen,” he said. But in some areas, like Hudson Bay, where polar bears are forced onto land for large chunks of the year because of the lack of sea ice, they may be food deprived for eight months.

Amstrup and other researchers have noticed the effect these changes are having on polar bear cub survival rate. Females are still breeding, but their cubs are not making it on to the next generation, he said.

“There are proximate and ultimate actions” we can take to help polar bears, Amstrup said. “If we believe that the vast majority of climate scientists are correct that humans are contributing to global warming, then the ultimate management action is to do something about greenhouse gases,” he said. “In the proximate sense, regardless of what’s going on, we need to keep understanding polar bears,” Armstrup added.

Robert Buchanan, president of Polar Bears International, and Daniel Cox, a professional wildlife photographer, also spoke. The event was organized by local couple and polar bear enthusiasts Valerie and Richard Beck.
PERMALINK:
Polar bears in danger from melting sea ice | Planet JH News Article: General Environment

Leave a Comment