Now we have too many polar bears? Bear population numbers ‘may now have reached its carrying capacity’
Exciting news about polar bears in eastern Canada: A peer-reviewed paper on the Davis Strait subpopulation study has finally been published in the Journal of Wildlife Management. It concludes that despite sea ice having declined since the 1970s, polar bear numbers in Davis Strait have not only increased to a greater density (bears per 1,000 km2) than other seasonal-ice subpopulations (like Western Hudson Bay), but may now have reached its carrying capacity.
In other words, this subpopulation is showing changes expected in populations affected by declines in sea ice or one that has reached its carry capacity (i.e. “negative effects of greater densities”) but that it is not possible to distinguish between the two.
This is actually not the first time this conclusion has been reached. In 2005, researcher Andrew Derocher stated in regards to his study of Svalbard area polar bears in the Barents Sea that “given that the population may be showing density-dependent responses, it is not possible to differentiate the climatic effects from population effects.” So, now we have at least two reports in the peer-reviewed literature that state flat out that the presumed negative effects of declining sea ice on a population’s size are indistinguishable from a population that is as large as it can get.
Hard to believe, isn’t it? Rather than being proven victims of Arctic sea ice in a “death spiral” due to global warming, when they finally present the data biologists have to admit that they cannot actually tell the difference between a polar bear population that is so large that it can no longer increase and one that is suffering a population decline because of reduced sea ice.
Susan Crockford, a zoologist, is adjunct professor (anthropology) at the University of Victoria, in Victoria, British Columbia. Ms. Crockford operates the blog site polarbearscience.com