South Beaufort Sea polar bear population dropped in early 2000s: study

New research associates decline with loss of sea ice due to climate change


A male polar bear along the Beaufort Sea near Alaska, photographed in 2005. (PHOTO BY STEVEN AMSTRUP)

A male polar bear along the Beaufort Sea near Alaska, photographed in 2005. (PHOTO BY STEVEN AMSTRUP)

A new study published by researchers from Canada and the United States suggests that the southern Beaufort Sea polar bear population saw a decline of about 40 cent in the early 2000s.

Researchers from the U.S. Geological Survey, Environment Canada and the University of Alberta used mark and recapture methods to monitor the population of bears along the northern coasts of Alaska and the Northwest Territories from 2001 to 2010.

Those were years, researchers note, when the summer sea ice extent was generally in decline.

The groups found that the survival of adult polar bears and cubs was especially low from 2004 to 2006, when most of the decline occurred.

“Of the 80 cubs observed in Alaska from 2004 to 2007, only two are known to have survived,” said Jeff Bromaghin, United States Geological Survey research statistician and lead author of the study.

The scientists consider that dip in population as likely due to a limited access to seals during that period. They say it’s also possible the seal population was lower in those years.

By 2007, polar bear adult and cub survival rates began to improve, researchers found, stabilizing at about 900 bears by 2010 — down from an estimated 1,500 in 2001.

But they’re not so sure why.

“The low survival may have been caused by a combination of factors that could be difficult to unravel,” said Bromaghin in a U.S. Geological Survey release Nov. 17, “and why survival improved at the end of the study is unknown.”

The organization continues to research and monitor the population, he added.

In the meantime, the Word Wildlife Fund Canada said the study’s findings highlight the need for action to reduce greenhouse gas emissions.

“This is a clear warning sign of the impact the warming Arctic has on ice-dependent species like the polar bear,” said Paul Crowley, WWF-Canada’s Arctic program director in a Nov. 17 release.

“Given that this subpopulation is at the edge of the range, these survey results do not come as a surprise,” he said.

“These findings also highlight the importance of high-quality and current information. We need to take action today on the main threat to polar bears: climate change.”

But the Nunavut government has previously dismissed forecasts from the U.S. Geological Survey, namely their claim that the world’s polar bear will die off in the next half century.

Other scientists have criticized the models used by some of the researchers who worked on this latest study.

There are 19 polar bear populations across the world.

According to the U.S Geological Survey, four of those populations — including the southern Beaufort Sea population — are considered to be declining. Five are stable, one is increasing, the USGS says, while the remainder are considered inconclusive.

The polar bear was listed as globally threatened under the U.S. Endangered Species Act in 2008 due to concerns about the effects of sea ice loss on their populations.

The study, titled “Polar bear population dynamics in the southern Beaufort Sea during a period of sea ice decline,” was published in the latest issue of Ecological Applications.

Other collaborators on the study include the U.S. Fish and Wildlife Service, Polar Bears International, and Western Ecosystems Technology.

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