I got an email from a reader suggesting that the high numbers for the world’s polar bear population, as given by the Polar Bear Specialist Group (PBSG) on their website in their State of the Polar Bear (SoPB) summary feature – as tallied by nation (22,600-32,000) – may simply be an error resulting from counting overlapping territories twice (i.e. where a subpopulation with one population estimate is shared by two nations, the total amount has been attributed to each nation, rather than giving each of them half of the total).
That is not the case and I’ll tell you why.
If you haven’t yet seen the last post, pop back and have a look – it’s short.
Then note the following:
1) Re: the numbers given for Russia (given as 2,700-4,800 in SoPB-by-nation). Russia has three subpopulations of polar bears: Chukchi (shared with the USA), Kara Sea and Laptev Sea. See previous post here on these estimates by the PBSG.
Chukchi officially has a population of zero because it has never been surveyed. The same is true for the Kara Sea: its population is officially zero and always has been. The Laptev Sea is given a tentative estimate of 800-1,200 in most subpopulation estimates but on the “State of the Polar Bear” summary, it is given as zero. Thus, at the very most, the total for Russia could be 800-1,200.
Conclusion: the estimate of 2,700-4,800 for the Chukchi Sea is not a result of an overlap in count. It’s a new number and there is no information given about where it comes from (it’s remotely possible that the SoPB-by-nation number comes from a recent survey of the Chukchi Sea, see previous post here, but that number has not been made public and the study results have not yet been published).
2) Re: numbers for the USA (given as 1,200-1,800 in SoPB-by-nation). The US has two subpopulations: Southern Beaufort (which it shares with Canada) and the Chukchi Sea (which it shares with Russia). The number usually given for the Southern Beaufort is 1,200-1,800 - so the US share is something like 600-900. While the US shares the Chukchi population with Russia, the Chukchi has never been surveyed – its population is officially zero (half of zero is still zero).
Conclusion: if there has been any “doubling up” going on, it is here. The official (documented) number for the US should be about 600-900.
3) Re: numbers for Greenland (given as 3,500-4,400 in SoPB-by-nation). East Greenland has never been surveyed and the official estimate for that subpopulation is zero. West Greenland comprises three polar bear subpopulations that it shares with Canada: Baffin Bay (total count 1,544-2,604), Davis Strait (total count 1,811-2,534) and Kane Basin (total count 94-234). That comes to 3,449-5,372. Conclusion: if there had been a “doubling” of shared population numbers, the number for Greenland should have been listed in the SoPB-by-nation map as 3,449-5,372 (not 3,500-4,400).
The estimate for the world’s polar bear population, as given by the Polar Bear Specialist Group (PBSG) on their website in their State of the Polar Bear summary feature – as tallied by nation (22,600-32,000) – is not simply an error resulting from counting overlapping territories twice.