Reports by the U.S. Geological Survey (USGS) suggest that the retreat of Arctic sea ice could reduce polar bear populations by as much as two thirds within 50 years, observes the Wildlife Management Institute. Furthermore, USGS concluded that the models appear to underestimate the loss of sea ice, which could make the projected decline a conservative estimate.

In January, U.S. Department of the Interior Secretary, Dirk Kempthorne, asked USGS to put together a research team to outline the breadth of knowledge and develop new research about climate change and the impact of retreating sea ice on polar bears. The findings, made available on September 7 as a series of nine administrative reports, will provide information to the U.S. Fish and Wildlife Service (FWS) as it considers the possible listing of polar bears as a threatened species under the Endangered Species Act.

The research team, including scientists from U.S. and Canadian government agencies and from the private sector, analyzed new and existing data on climate models and on polar bears and their habitats in the northern and southern Beaufort Sea and the southern Hudson Bay. It documented the dependence of polar bears on sea ice, which is used as a platform to hunt seals.

Using 10 general circulation climate models and assuming business-as-usual greenhouse gas emissions, USGS projects a 42 percent loss by midcentury of optimal polar bear habitat in the Polar Basin during summer, the most critical hunting and breeding period. Sea ice will reform each winter, but the large retreats of sea ice in summer may prevent bears from returning to onshore denning sites. USGS states that sea ice conditions would have to be substantially better than even the most conservative projections to result in qualitatively different outcomes for polar bears across the region.

The FWS will open the research for public comment and will consider the USGS reports with other relevant and scientifically accurate research in its listing decision. The decision is expected by January 2008.