Global Warming Could Doom Polar Bears

Dan Shapley / News Editor

In a sobering report, the U.S. Geologic Survey predicts that 2/3 of the world's polar bear population will have disappeared within 50 years, as global warming destroys the Arctic ice they depend on. Polar bears depend on sea ice as a platform to hunt seals, their primary food. But sea ice is decreasing throughout their Arctic range due to climate change.

Models used by the USGS team project a 42% loss of optimal polar bear habitat from the Polar Basin during summer, a vital hunting and breeding period, by mid-century. This year, scientists documented the lowest extent of Arctic sea ice ever recorded -- and the record was set a full month before the annual retreat of ice had completed its cycle. Scientists have documented melting in the region that far outpaces the expectations in U.N. climate reports -- suggesting that the region is responding much faster to global warming than is widely thought.

The report is a landmark conglomeration of studies by various scientists, and amounts to a strong statement in support of listing polar bears as a threatened species protected by the Endangered Species Act. The Fish and Wildlife Service is expected to make a recommendation on that proposal in January. The USGS study focused on the status of three polar bear sub-populations, projected numbers of polar bears into the future in relation to sea ice and integrated the information into a range-wide assessment of polar bear status under scenarios of future climate change.

During a six-month period of intensive analysis of both existing and new data, the team documented the direct relationship between the presence of Arctic sea ice and the survival and health of polar bears. In addition to forecasts, declines in habitat have been recorded throughout the Polar Basin over the past 20 years of observations. To project future sea ice conditions, USGS scientists used 10 general circulation models that best approximated observed trends in sea-ice loss and could be expected to do the best job of simulating future conditions.

Scientists characterize their conclusions as conservative because even the best available models are believed to underestimate the actual decline in Arctic sea ice. To read more about the report, click here.

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