WASHINGTON(Reuters)Twothirds of the world's polar bear population could be gone by 2050 if predictions of melting sea ice hold true, the U.S.Geological Survey reported on Friday.
The fate of polar bears could be even worse than that estimate, because sea ice in the Arctic might be disappearing faster than the available computer models predict, the geological survey said in a report aimed at determining whether the big white bear should be listed as a threatened species.
"There is a definite link between changes in the sea ice and the welfare of polar bears," said Steve Amstrup, who led the research team.He says Arctic sea ice is already at the lowest level this year and is expected to retreat(退却)farther this month.
That means that polar bears some 16,000 of them will disappear by 2050 from parts of the Arctic where sea ice is melting most rapidly, along the north coasts of Alaska and Russia, researchers said in a telephone briefing(简报).
Other polar bear populations could survive beyond that date but many of those could be gone by 2100, Amstrup said.By century's end, the only polar bears left might live in the Canadian Arctic islands and along the west coast of Greenland.
"It is likely to result in loss of approximately twothirds of the world's current polar bear population by the mid 21st century," the report summary said.
"Because the observed trajectory(轨迹)of Arctic sea ice decline appears to be underestimated(低估)by currently available models, this assessment of future polar bear status may be conservative(保守的)."
In January, the U.S.Fish and Wildlife Service suggested listing the polar bear as a threatened species, noting polar bears depended on sea ice as a platform to hunt seals, their main food.
Without enough sea ice, polar bears would be forced onto land, but they are inefficient hunters once they get out of the water and ice, the researchers said.The bears' disappearance would probably take place as young cubs(幼兽)failed to survive to adulthood and females were unable to reproduce successfully.
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