Polar Bear Population Plummets 40 Percent in 10 Years

A key polar bear population in Alaska has plummeted 40 percent in the last 10 years, marked by a dramatic increase in deaths of young cubs, according to a new study published Monday.

Scietists from the US Geological Survey (USGS) and Environment Canada found that bear survival rates in the south Beaufort Sea, located off Alaska and northwestern Canada, are particularly low.

Monitoring of this bear population began in 2001, and since then overall survival rates began to climb; however, juvenile bears are in jeopardy. From 2004 to 2006, for example, only two of 80 studied cubs were known to have survived. And as of 2010, the end of the 10-year study period, polar bears are down to about 900 individuals.

"The low survival may have been caused by a combination of factors that could be difficult to unravel, and why survival improved at the end of the study is unknown," lead author Jeff Bromaghin with the USGS said in a statement.

Normally half of the cubs manage to survive, but Bromaghin and his team suspect that the lack of summer sea ice - a result of climate change - makes it more difficult for bears to catch seals. Although some bears in this population have adapted and come ashore during the autumn open water period, most stay with the sea ice as it retreats north into the Arctic Basin and far from shore where few seals are found.

"In 2007, my colleagues and I predicted we could lose polar bears from the southern Beaufort Sea by the middle of this century if we didn't get on to a different greenhouse gas emissions path," Dr. Steven Amstrup, chief scientist at Polar Bears International, told The Guardian. "This report confirms we still are on the wrong path."

It is possible that seal numbers are down in general, but only further research and continued monitoring can give scientists the answer.

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

The study was published in the journal Ecological Applications.