This is a follow-up to my last post, which summarized IUCN/SSC Polar Bear Specialist Group (PBSG) polar bear population estimates and status reports, here.
I was interested to see how the PBSG population estimates compared to similar studies in other animals, so I took a look at the official 2012 population estimate for grizzly bears in British Columbia, Canada here. A couple of brief excerpts are provided below.
British Columbia is the western-most province of Canada (Fig. 1). It is roughly half the size of Greenland, while sea ice habitat of polar bears is roughly 6-7x the area of Greenland.
Just nine pages long, this grizzly bear population report is short, clear and unambiguous. While it may perhaps not explain its methods in enough detail for some folks (and it is, admittedly, a small portion of global grizzly bear territory), the report is nevertheless clear about the variations in quality of population estimates over time (which began in the 1970s and so are similar to what we have for polar bears). The report is also clear about how these historical estimates impact the current population status and trend. See Fig. 2 and 3 below for short excerpts.
Excerpts from the 2012 BC grizzly bear population estimate below
While there are of course some distinct differences in the material and circumstances under consideration for British Columbia grizzlies in 2012 and circumpolar populations of polar bears in 2009, there are also many similarities. One of those similarities is the scarcity of good quality historical data for management units within the geographic ranges under consideration. However, in contrast to the 2009 PBSG report, the authors of the 2012 BC grizzly bear population estimate refrained from making status and population trend assessments when it was apparent that it was not possible to back up such assessments with reasonably accurate data.
Anonymous. 2012. British Columbia Grizzly Bear Population Estimate for 2012. Report from the Ministry of Forests, Lands and Natural Resource Operations. April 2012. Available online.