A key polar bear population fell nearly by half in the past decade, marked by a dramatic increase in deaths of young cubs, a new U.S.-Canada study says. Researchers chiefly blame shrinking sea ice from global warming. Scientists from the U.S. Geological Survey and Environment Canada tagged and released polar bears in the southern Beaufort Sea off Alaska and northwestern Canada from 2001 to 2010. The bear population shrank to about 900 in 2010, down from about 1,600 in 2004.
Study lead author Jeff Bromaghin said only two of 80 polar bear cubs the team tracked between 2004 and 2007 survived. Normally about half of cubs live. He thinks the cubs starved because there was a lack of summer sea ice and they couldn't get to seals. The study is in the journal Ecological Applications.
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