Wednesday, March 28, 2007

Lies, damned lies and polar bear statistics

Here is just another example of how difficult it is to get hard, definitive information on global warming and related issues.
The Globe and Mail's Margaret Wente was the goad, as she so often is, with her bald statement that polar bears are not threatened or suffering from climate change at all, but on the contrary are thriving and increasing in numbers.
That sounded wrong to me (as Ms. Wente's claims so often do), particularly as I remember a previous column of hers from some months ago where she made similar claims, based on the fact that, when she visited Churchill, Manitoba, there seemed to be lots of white bears around.
So, I thought I would check up on the facts, only to discover that it is not quite as simple as either I (or Ms. Wente) thought.
I can understand that, if the sea ice flows (their normal hunting grounds) are smaller or breaking up, more bears are likely to be seen on land, but I wanted some convincing evidence that the overall populations are increasing or decreasing.
A quick Google search revealed a whole heap of contradictory results, several claiming that polar bears are suffering badly, and several assuring exactly the opposite. Most of them (on both sides) did not seem to be based on any hard evidence.
I delved further, and possibly the most convincing and detailed analysis I could find was by the World Wildlife Fund. Although they are admittedly not exactly impartial, they are at least reputable and their analysis seems to be based mainly on the latest report by the Polar Bear Specialist Group of the World Conservation Union ( a dense and turgid report which seemed to go out of its way NOT to give any easily digestible overall conclusions).
What seems indisputable is that there are 19 populations of polar bears in the Arctic, (in Canada, Alaska, Russia, Norway and Greenland), 13 of which are either wholly or partially in Canada, mainly in the Northwest Territories. Clearly it is a mite tricky keeping track of these critters, given their habitat and their habits, but the best current estimate of total numers is 20,000-25,000 (which leaves a fair margin for error), of which about two-thirds are in Canada.
The WWF website goes on to list the estimates for the Canadian populations, with recorded dates varying between 1986 and 2006, and a Status, Trend and Estimated Risk of Decline for each, which is where things start to get a little muddled. The table suggests that 2 populations are severely reduced from historic levels, 4 reduced, 6 "not reduced" (presumably a euphemism for "increased") and 1 "data deficient"(?).
The WWF's summary, however, interprets this as 5 declining, 5 stable and 1 unknown ("for the 11 populations not known to be severely reduced from historic levels"). This almost seems to be deliberate obfuscation, and frankly I am not much wiser now than I was before.
It seems pretty clear than some populations are declining and some are increasing, but whether that just means that they are moving around more, and whether the overall population is waxing or waning (or neither) from, say, 20 or 30 years ago, I still have no idea.

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