Effects of future warming on polar bear populations and other Arctic species

If climate warming continues unchecked, the persistence of many polar bear populations is doubtful. Recently, the members of the IUCN/SSC Polar Bear Specialist Group, representing the scientific and management expertise of the five nations with polar bear populations (Russia, Norway, Denmark/Greenland, Canada and the US), unanimously raised the level of conservation concern for the species. Polar bears are now listed as 'Vulnerable', which means they are considered to be facing a high risk of extinction in the wild. The timeframe of concern varies for each population, but a global decline exceeding 30 per cent is possible within the next 35 to 50 years; if this were to occur, the world could lose over 8000 polar bears within three generations of bears. Faced with this prospect, future challenges for conserving polar bears and their Arctic habitat will be greater than at any time in the past because of the rapid rate at which environmental change is occurring.

One area that will likely enter conservation plans in coming years is the reduction of polar bear harvest by local people. While to some this may seem like a simple and logical solution, this response will victimize northern people who are already being severely affected by climate change. Inuit have lived with and hunted polar bears for thousands of years. Loss of harvest rights will have negative social, cultural and economic consequences. It is important to note that each subpopulation will show the signs of climate warming at different times and a blanket policy to close harvest is unnecessary as long as a sustainable harvest is available.

Some have naively suggested that polar bears will adopt a more terrestrial lifestyle and adapt back to the ways of their ancestral species. Unfortunately, for a species like the polar bear, the changes may be too fast. Evolution in large mammals with long generation times occurs over tens or hundreds of thousands of years, not decades or centuries. Further, the terrestrial niche for an Arctic bear is already occupied and there are indications that barren-ground grizzlies are already advancing northward. History has shown that large and highly specialized species generally do not fair well with rapid changes in their environment.

It is more than just polar bears that are threatened: all ice-dependent species are at risk. In particular, Arctic marine mammals that rely on sea ice are at risk of being negatively affected. Both Arctic seals and whales rely on the presence of sea ice. As the sea ice disappears, there will be a shift towards species from the north Atlantic and north Pacific oceans. If the ice retreats too far, ringed and bearded seals will be replaced by harbor and harp seals and the narwhal and white whales will slip away as killer whales (Orcinus orca) take over the top predator role. Northern baleen whales such as the abundant minke whale (Balaenoptera acutorostrata) would likely expand into the previously ice-covered waters. A new ecosystem will emerge but it will be one without polar bears.

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