Two-thirds of all polar bears may be lost in 50 years

This warning follows a request to the USGS by the US Secretary of the Interior Dirk Kempthorne to help decide whether or not to recommend listing the polar bear as a threatened species.

Polar bears are losing their icy habitat in the Arctic and some scientists predict they will become extinct. (Photo courtesy Greenpeace UK)

"This team has done a tremendous job in furthering polar bear science through the use of long-term observational measurements on polar bears, their habitats, and many other factors integrated into a range of new and traditional models," said Mark Myers, Director of the US Geological Survey.

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. 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 per cent loss of optimal polar bear habitat from the Polar Basin during the summer hunting and breeding period, by mid-century.

The polar bear habitat has been shrinking 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 simulate future conditions as well as possible. Scientists say their conclusions as conservative because even the best available models probably underestimate the actual decline in Arctic sea ice.

The US Fish and Wildlife Service are due to announce their decision on the listing of the polar bear as 'threatened' in January.

The nine USGS reports can be seen at www.usgs.gov/newsroom/special/polar%5Fbears.

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