Polar Bears In Depth
Management and Conservation
Page 4 of 5
Global Warming. With reasonable management flexibility, the future of the polar bear as it relates to interactions with humans appears bright. Even in areas of intense industrial activity, such as the Alaskan Beaufort Sea, polar bear populations have flourished. Given adequate vigilance, humans and polar bears should be able to continue to coexist for the foreseeable future.
Significant larger concerns loom on the horizon, however. Evidence that the average temperatures of the globe are increasing continues to mount (Stirling and Derocher 1993). Along with increasing temperatures, the extent of the sea-ice in the Northern Hemisphere has declined from about 12.5 to 11.5 million km2 during the past 25 years (Gloersen and Campbell 1991; Vinnikov et al. 1999). Reductions in the amount of time polar bears of southern regions can spend hunting on the sea-ice already may have resulted in significant declines in productivity. Body weights of female polar bears and numbers of independent yearlings have declined, while reproductive intervals have increased at the same time the sea-ice of Hudson Bay has been melting earlier in summer (Stirling et al. 1999). Because Hudson Bay is at the southern extreme of polar bear range (see Figs. 27.1 and 27.8), the effects of warmer temperatures and earlier ice melt are likely to be felt there sooner than in more northerly parts of the polar bear range. In fact, in areas where the heavy sea-ice limits access to food (Messier et al. 1992; Ferguson et al. 2000b) and where productivity traditionally has been lower than Hudson Bay (Amstrup et al. 1986, 2000), a milder climate may actually benefit polar bears in the short run. Thinner ice cover and shorter ice seasons of time could enhance primary productivity in northerly areas and such increases could be passed through the food chain. Ultimately, however, if sea-ice cover continues to decline, polar bears worldwide will suffer. Polar bears are so closely tied to the presence of the sea-ice platform from which to hunt, mate, and carry on other life functions that continuing extensive declines in ice coverage will restrict their productivity and could ultimately threaten their survival.
Significant larger concerns loom on the horizon, however. Evidence that the average temperatures of the globe are increasing continues to mount (Stirling and Derocher 1993). Along with increasing temperatures, the extent of the sea-ice in the Northern Hemisphere has declined from about 12.5 to 11.5 million km2 during the past 25 years (Gloersen and Campbell 1991; Vinnikov et al. 1999). Reductions in the amount of time polar bears of southern regions can spend hunting on the sea-ice already may have resulted in significant declines in productivity. Body weights of female polar bears and numbers of independent yearlings have declined, while reproductive intervals have increased at the same time the sea-ice of Hudson Bay has been melting earlier in summer (Stirling et al. 1999). Because Hudson Bay is at the southern extreme of polar bear range (see Figs. 27.1 and 27.8), the effects of warmer temperatures and earlier ice melt are likely to be felt there sooner than in more northerly parts of the polar bear range. In fact, in areas where the heavy sea-ice limits access to food (Messier et al. 1992; Ferguson et al. 2000b) and where productivity traditionally has been lower than Hudson Bay (Amstrup et al. 1986, 2000), a milder climate may actually benefit polar bears in the short run. Thinner ice cover and shorter ice seasons of time could enhance primary productivity in northerly areas and such increases could be passed through the food chain. Ultimately, however, if sea-ice cover continues to decline, polar bears worldwide will suffer. Polar bears are so closely tied to the presence of the sea-ice platform from which to hunt, mate, and carry on other life functions that continuing extensive declines in ice coverage will restrict their productivity and could ultimately threaten their survival.