An exhibition display shows a polar bear crossing a mound of human refuse.

Denis Finnin/AMNH

Polar Bear

                                                                                          What has happened to this magnificent animal? Climate change has altered the rhythms of its life. For much of the year, sea ice is the hunting ground and home of the polar bear (Ursus maritimus). When the ice breaks up, the bears retreat to the edge of the shrinking icepack or to ice-covered land. There, they enter into a nonhunting state sometimes called walking hibernation.

But today, the sea ice in many places is retreating earlier and returning later. This forces some of the bears to subsist for longer periods on land, where they may come in contact with humans—and their trash. Residents of many towns in the Arctic report more "problem bears"—hungry animals that forage in populated areas, including in refuse dumps.

Nesting Ground

The endangered red-breasted goose (Branta ruficollis) builds its nest on the edges of cliffs in the Arctic. As the underlying permafrost melts, the cliffs lose structural stability and the edges collapse, destroying the nests. Some experts say this bird will lose two-thirds of its European Arctic breeding ground if temperature warms 1.7°C (3°F)—an amount of warming that will be difficult to avoid.

Arctic Specialists

Many whales feed in summer in the high Arctic, then go south to breed. The strangely beautiful mammals called narwhals (Monodon monoceros) do the opposite. True Arctic specialists, they feed under the pack ice in winter, mostly on Greenland halibut, at a depth of 1,500 meters (about 5,000 feet). The consequences of warming, including diminishing sea ice, higher water temperature, and changing ocean currents, will influence the whales in ways that are difficult to predict.