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The Fourth Report of the IPCC (The United Nations' Intergovernmental Panel on Climate Change), Climate Change 2007, reported as follows:
Polar Bears (Ursus maritimus), estimated numbers 20,000 to 25,000 worldwide, live on the annual sea-ice of the Arctic. They may wander thousands of kilometres every year. They live on ice-breeding seals, so the bears need sea-ice for survival.
Female bears need to feed when they emerge with their cub(s) each spring from a nursing den. They have had no food for 5 to 7 months.
If there is continuous sea ice, bears can hunt all through the year, but in areas where the sea ice melts each summer, bears have to spend several months on tundra, living on their stored fat reserves, till the sea freezes again.
Polar bears face great challenges, because projected reductions in sea ice will dramatically shrink their habitat.
The sea ice in Western Hudson Bay, Canada, now melts 3 weeks earlier than in the early 1970s. Bears now come ashore earlier with smaller fat reserves (15%), they fast for longer and they have fewer cubs. This population appears to have declined from 1200 bears in 1987 to fewer than 950 in 2004. It is reasonable to expect that other populations may be similarly impacted.
In 2005, the IUCN Polar Bear Specialist Group recommended that polar bears should be upgraded from Red List Least Concernto Vulnerable, because of the likelihood of an overall decline in the total population of more than 30% in 35 to 50 years' time.
If sea ice declines according to some projections, polar bears face a high risk of extinction with a global warming of 2.8ºC above pre-industrial temperature.
Source: Climate Change 2007: Working Group II: Impacts, Adaptation and Vulnerability: 4.4.6 Tundra and Arctic/Antarctic ecosystems (see the link below).
The Fourth Report of the IPCC, published in 2007, included findings that polar bears are highly vulnerable to climate change due to their reliance on sea ice for hunting. It highlighted that reductions in sea ice extent directly impact the bears' ability to find food and may ultimately threaten their survival. Additionally, the report addressed the increasing threats that climate change poses to polar bear populations in the Arctic.
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