Polar bears live only in marine regions of the Northern Hemisphere where sea-ice cover persists for long enough to allow them sufficient opportunity to access their marine mammal prey. Recent declines in summer Arctic sea ice have coincided with declines in some polar bear populations, and a US Geological Survey report in 2007 projected that with ‘business as usual’ emissions, polar bears could be extinct throughout their range by the end of the century. Some observers have suggested that summer Arctic sea ice might already have crossed a tipping point from beyond which habitats might not recover. But a new analysis suggests that it is not too late to save the polar bear. The rapid summer ice losses seen of late may represent increased volatility of a thinning sea-ice cover, rather than a tipping point. Greenhouse-gas mitigation could yet halt sea-ice loss and preserve the Arctic ecosystem.
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