POSSIBLE IMPACTS OF CLIMATIC WARMING ON POLAR BEARS

If climatic warming occurs, the first impacts on polar bears (Ursus ma ritimus) will be felt at the southern limits of their distribution, su ch as in James and Hudson bays, where the whole population is already forced to fast for approximately four months when the sea ice melts du ring the summer- Prolonging the ice-free period will increase nutritio nal stress on this population until they are no longer able to store e nough fat to survive the ice-free period. Early signs of impact will i nclude declining body condition, lowered reproductive rates, reduced s urvival of cubs, and an increase in polar bear-human interactions. Alt hough most of these changes are currently detectable in the polar bear s of western Hudson Bay, it cannot yet be determined if climatic chang e is involved. In the High Arctic, a decrease in ice cover may stimula te an initial increase in biological productivity. Eventually however, it is likely that seal populations will decline wherever the quality and availability of breeding habitat are reduced. Rain during the late winter may cause polar bear maternity dens to collapse, causing the d eath of occupants. Human-bear problems will increase as the open water period becomes longer and bears fasting and relying on their fat rese rves become food stressed. If populations of polar bears decline, harv est quotas for native people will be reduced and eventually be elimina ted. Tourism based on viewing polar bears in western Hudson Bay will l ikely disappear. Should the Arctic Ocean become seasonally ice free fo r a long enough period, it is likely polar bears would become extirpat ed from at least the southern part of their range. If climatic warming occurs, the polar bear is an ideal species through which to monitor t he cumulative effects in arctic marine ecosystems because of its posit ion at the top of the arctic marine food chain.