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　　Polar bears depend on ice to hunt(獵取)for food in the Arctic Ocean．They climb up on the ice to look for seals and other animals．But scientists say sea ice is decreasing(減少)because of climate change．They say rising temperatures have reduces the area in which polar bears can hunt．

　　Recently, a number of studies found that future reductions(減少)of sea ice could result in a loss(消失)of many polar bears within fifty years．The studies found a direct link between sea ice in the Arctic Ocean and the health of polar bears．The scientists say the animals will disappear from the north coasts of Alaska and Russia in the next fifty years．The only polar bears to survive will be in Canada's far north and the west coast of Greenland．

　　The scientists found that almost two thirds of the world's nineteen polar bear populations will disappear from the earth by the middle of this century．The studies showed that three more groups of polar bears will disappear within seventy-five years．

　　Scientists say polar bears still can be saved．But they say the world must begin taking steps to reduce climate change to do this．The center for Biological Diversity says governments around the world need to reduce the release(釋放)of pollution like CO₂ gas．

　　Scientists say one step toward this goal would be to include polar bears on America's list of endangered(有危險(xiǎn)的)species．Then the government would be able to make sure that industrial activities do not threaten their survival．The United States Fish and Wildlife Service is expected to examine the new findings when it considers whether polar bears should be included on the Endangered Species List．