In my State of the Polar Bear 2023 report for the World Warming Coverage Basis, I talk about latest information related to polar bear conservation and science points. Probably the most startling of those is the revelation that Western Hudson Bay polar bear numbers haven’t declined since 2004.
Press launch (27 February 2024), World Warming Coverage Basis
50 years after looking ban polar bears are thriving, new report reveals
London, 27 February: 2023 marked 50 years of worldwide cooperation to guard polar bears throughout the Arctic. These efforts have been a conservation success story: from a inhabitants estimated at about 12,000 bears within the late Sixties, numbers have virtually tripled, to simply over 32,000 in 2023.
Regardless of this dramatic improve in polar bear populations, claims that their numbers are falling as a result of local weather change nonetheless dominate most media protection.
Since 2004 we have been informed that polar bear numbers in Western Hudson Bay have been steadily declining, however a brand new examine made public in 2023 reveals that this isn’t really true. Within the State of the Polar Bear Report 2023, printed by the World Warming Coverage Basis (GWPF) on Worldwide Polar Bear Day, zoologist Dr. Susan Crockford supplies the small print on this explosive information.
Amongst different points addressed on this yr’s report, Crockford explains that inhabitants surveys of Western Hudson Bay polar bears accomplished in 2011, 2016, and 2021 generated decrease estimates than a survey achieved in 2004. Nonetheless, these variations in bear counts aren’t statistically important from one another, which implies there was no unfavorable pattern over the past 20 years.
Crockford mentioned the implications of this survey are huge.
“It means there was no statistically important pattern in Western Hudson Bay polar bear numbers since a minimum of 2004. This consequence completely guts pc mannequin predictions of future polar bear disaster that assume Western Hudson Bay numbers have been steadily declining.”
She additionally mentioned the Western Hudson Bay survey raised questions on previously-unknown actions of a whole bunch of bears throughout subpopulation boundaries in Hudson Bay.
“There may be now pretty robust proof that the subpopulation boundaries in Hudson Bay must be adjusted and have their earlier inhabitants estimates recalculated. The same concern is acknowledged in Alaska, the place for many years pretty massive numbers of Southern Beaufort polar bears have moved backwards and forwards over the present boundary between the Chukchi Sea to the west and the Northern Beaufort Sea to the east. Which means in case you depend Southern Beaufort bears in a single space at one cut-off date, it might appear to be a inhabitants decline has taken place when it really hasn’t.”
Crockford added, “Western Hudson Bay and the Southern Beaufort are the one polar bear subpopulations which appeared to indicate robust help for the premise that sea ice declines blamed on human-caused international warming have decreased bear abundance. Now we all know earlier claims are virtually actually incorrect.”
Key Findings
There have been no stories from the Arctic in 2023 indicating polar bears had been being harmed as a result of lack of summer season sea ice habitat, partially as a result of Arctic sea ice in summer season has not declined since 2007.
Opposite to expectations, a examine in Svalbard discovered a lower in polar bears killed in protection of life or property over the past 40 years, regardless of profound declines in sea ice over the past twenty years.
A survey of Southern Hudson Bay polar bears in 2021 confirmed an astonishing 30% improve over 5 years, which provides one other 223 bears to the worldwide complete.
A concurrent survey of Western Hudson Bay polar bears in 2021 confirmed that numbers had not declined since 2011, which additionally means they haven’t declined since 2004. Motion of bears throughout boundaries with neighbouring subpopulations could account for the looks of a decline, when none really occurred.
The IUCN Polar Bear Specialist Group has ignored a 2016 suggestion that the boundaries of three Hudson Bay subpopulations (Western HB, Southern HB, and Foxe Basin) be adjusted to account for genetic distinctiveness of bears inhabiting the Hudson Bay area; an analogous boundary concern within the western Arctic between the Chukchi Sea, and the Southern and Northern Beaufort subpopulations, based mostly on recognized actions of bears between areas, has been acknowledged since 2014 however has not but been resolved.
The US Fish and Wildlife Service and the IUCN Polar Bear Specialist Group, of their 2023 stories, did not formally acknowledge the new-found South-East Greenland inhabitants because the twentieth subpopulation, regardless of undisputed proof it is a genetically distinct and geographically remoted group. Numbers are estimated at 234 people.
Quotation for the report: Crockford, S.J. 2024. State of the Polar Bear 2023. Briefing Paper 67. World Warming Coverage Basis, London. Obtain pdf right here.
Backgrounder: Western Hudson Bay inhabitants surveys
Here’s a brief abstract of Western Hudson Bay (WH) polar bear inhabitants measurement survey outcomes since 1987, which incorporates the 95% confidence interval calculated (listed because the ‘vary’ of potential correct estimates) for every imply estimate. These surveys used a dizzying mixture of discipline strategies, geographic areas coated throughout the WH subpopulation boundary (see map under), and mathematical fashions to generate inhabitants estimates.
1987, based mostly on geographically-restricted (Space C solely) capture-recapture examine: 1184 (vary 993-1411), calculated by Lunn et al. (2016:1313) for comparability to their 2011a examine; observe this determine is barely completely different (i.e., 1194, vary 1020-1368) than utilized by Regehr et al. (2007) to match to 2004 information.
2004, based mostly on geographically-restricted (Space C solely) capture-recapture examine: 935 (vary 794-1076), a statistically insignificant decline of twenty-two% since 1987 (Regehr et al. 2007:2679).
2011a, based mostly on geographically-restricted capture-recapture (Space C + a few of Space B): 806 (653-984) is the one most frequently quoted (Lunn et al. 2013, 2016). As occurred in 2022 concerning the 2021 survey, in 2013 polar bear researchers shared outcomes of the 2011 survey with the media earlier than the report was obtainable to the general public.
2011b, based mostly on complete aerial survey: 1030 (vary 754-1406), accepted by the PBSG in 2014 (Stapleton et al. 2014; see additionally PBSG 2023).
2011c, 949 (vary 618-1280) is a recalculation of the 2011b estimate to make it corresponding to 2016 and 2021 (see Dyck et al. 2017:3).
2016, based mostly on an aerial survey with some variations from 2011b aerial survey: 842 (vary 562-1121) (Dyck et al. 2017)
2021, based mostly on an aerial survey with some variations from 2011b aerial survey: 618 (vary 385-852), not statistically completely different from the 2016 or 2011a estimates. Atkinson et al. 2022:29 said (my daring): Estimates derived for the WH subpopulation point out a potential decline in complete bear abundance between 2011 and 2021. …Though variations amongst these estimates [for 2011, 2016, and 2021] weren’t statistically important, complete abundance has declined constantly between successive surveys.
They are saying that “complete abundance has declined constantly between successive surveys” as if that over-rules the earlier assertion nevertheless it doesn’t. The principles of arithmetic say that with out statistical significance, there was no decline over time, as I clarify under.
With two exceptions, all WH inhabitants measurement estimates since 1987 aren’t statistically completely different from one another due to the overlap of their ‘confidence intervals’ (i.e., the ‘vary’ of potential appropriate estimates (e.g., 993-1411 for 1987). As proven within the chart above, the primary and final survey years (1987 and 2021) have clear non-overlapping confidence intervals (marked **), with the caveat that totally completely different strategies had been used for these estimates, so the we needs to be cautious concluding that an actual decline in abundance has taken place.
And whereas the 2011a estimate has a non-overlapping confidence interval in comparison with 1987 (marked *), indicating a statistically important decline between 1987 and 2011, the interval does overlap with the estimate for 2004 and for each different estimate since then. This implies that no definitive declining pattern in WH polar bear abundance could be mentioned to have occurred between 2004 and 2021.
Due to this fact, the complete aerial survey (2011b) which generated an estimate of 1030 bears is probably going nonetheless one of the best evaluation of abundance — and since additionally it is not statistically completely different from the 1987 estimate, it suggests the WH inhabitants has most likely been secure for greater than three a long time.
Polar bear researchers proceed to make public statements claiming {that a} steady inhabitants decline has occurred in WH when the information they’ve collected merely don’t help that conclusion. They defend this falsehood by insisting that numbers of grownup females and subadults have declined considerably the final 20 years, simply as they predicted would occur as a result of declining sea ice.
However in keeping with their very own information, sea ice situations haven’t declined over the past twenty years. There was a step-change in breakup and freeze-up dates that occurred about 1998, which in most years added about three weeks to the size of time that WH polar bears needed to stay onshore. Since then there was no change within the size of the onshore interval, which they freely admit (Atkinson et al. 2022; Castro de la Guardia et al. 2017; Lunn et al. 2013, 2016; Miller et al. 2022; Stapleton et al. 2014).
And if lack of sea ice isn’t driving the obvious decline in grownup females and subadult, what’s? Motion between subpopulation boundaries, particularly into Foxe Basin, is one robust chance that has not been adequately addressed. See the polar bear report for particulars.
Atkinson, S.N., Boulanger, J., Campbell, M., Trim, V. Ware, J., and Roberto-Charron, A. 2022. 2021 Aerial survey of the Western Hudson Bay polar bear subpopulation. Closing report back to the Authorities of Nunavut, 16 November 2022.
Castro de la Guardia, L., Myers, P.G., Derocher, A.E., Lunn, N.J., Terwisscha van Scheltinga, A.D. 2017. Sea ice cycle in western Hudson Bay, Canada, from a polar bear perspective. Marine Ecology Progress Collection 564: 225–233. http://www.int-res.com/abstracts/meps/v564/p225-233/
Dyck, M., Campbell, M., Lee, D., Boulanger, J. and Hedman, D. 2017. Aerial survey of the Western Hudson Bay polar bear sub-population 2016, remaining report (26 June 2017). Standing report 2017-xx, Nunavut Division of Atmosphere, Wildlife Analysis Part. Igloolik, Nunavut. pdf right here.
Lunn, N.J., Stirling, I., Andriashek, D. and Kolenosky, G.B. 1997. Re-estimating the scale of the polar bear inhabitants in Western Hudson Bay. Arctic 50(3): 234-240.
Lunn, N.J., Regehr, E.V., Servanty, S., Converse, S., Richardson, E. and Stirling, I. 2013. Demography and inhabitants evaluation of polar bears in Western Hudson Bay, Canada. Atmosphere Canada Analysis Report. 26 November 2013. PDF HERE
Miller, E.N., Lunn, N.J., McGeachy, D., and Derocher, A.E. 2022. Autumn migration phenology of polar bears (Ursus maritimus) in Hudson Bay, Canada. Polar Biology 45:1023-1034.
PBSG. 2023. ‘Standing Report on the World’s Polar Bear Subpopulations’. IUCN Polar Bear Specialist Group, 17 October. https://www.iucn-pbsg.org/
Regehr, E.V., Lunn, N.J., Amstrup, S.C., and Stirling, I. 2007. Results of earlier sea ice breakup on survival and inhabitants measurement of polar bears in western Hudson Bay. Journal of Wildlife Administration 71(8):2673-2683.
Stapleton S., Atkinson, S., Hedman, D., and Garshelis, D. 2014. Revisiting Western Hudson Bay: utilizing aerial surveys to replace polar bear abundance in a sentinel inhabitants. Organic Conservation 170:38-47. http://www.sciencedirect.com/science/article/pii/S0006320713004618#
