From Polar Bear Science
Posted on May 18, 2020 |
Facebook has labelled a recent short PragerU polar bear video as “false information” based on a ClimateFeedback review featuring statements by Andrew Derocher and Ian Stirling published 18 May 2020.
I was approached yesterday by Nick Coltrain, a reporter for the Des Moines Register and USA Today, asking for a statement about the accuracy of the PragerU video, which cites me as a source for two of their three ‘inconvenient facts.’
My comments are below but I reminded Nick that what is going on is a classic conflict that happens all the time in science: it presents no proof that I’m wrong or that the PragerU video is ‘false information’. Climate Feedback is not ‘factchecking’: it is presenting its preferred side of a disputed science issue.
Statement sent to Nick Coltrain:
Thanks for the opportunity to respond. I stand behind the accuracy of the video but wish they had cited my scientific paper, my fully referenced new book, The Polar Bear Catastrophe That Never Happened, and/or The State of the Polar Bear Report 2019, also fully referenced. [links provided to Crockford 2017, 2019, 2020]
I will post a full response on my blog but would like to point out the following.
Regarding the challenge of the adjective ‘thriving’ used in the video, in the review both Derocher and Stirling referred to Barents and Chukchi Sea polar bears as doing “OK”. I contend this is a gross misrepresentation of the published literature on these bears. There have been a number of papers published on Chukchi Sea bears documenting that body condition and reproduction are better now than in the 1980s and a recent paper on the body condition of female Barents Sea bears stated:
“Unexpectedly, body condition of female polar bears from the Barents Sea has increased after 2005, although sea ice has retreated by ∼50% since the late 1990s in the area, and the length of the ice-free season has increased by over 20 weeks between 1979 and 2013. These changes are also accompanied by winter sea ice retreat that is especially pronounced in the Barents Sea compared to other Arctic areas” [Lippold et al. 2019:988]
Biologically speaking, since the premise of the assumption that polar bear populations will decline with reduced summer sea ice is that bears will be in poor condition and reproducing poorly, it is logical to assume that bears with good body condition and reproducing well belong to thriving populations, regardless of the fact that the sea ice in their region is much reduced.
In addition, Stirling further stated that “…a couple [subpopulations] are doing OK, such as Foxe Basin and Davis Straight, and one seems to be increasing (M’Clintock Channel).” It is odd that Stirling fails to mention Kane Basin, shown on the status map provided as also ‘likely increasing’ (as documented in 2016 population survey report) and yet mentions M’Clintock Channel bears seem to be increasing even though the results of a long-awaited population survey, now long overdue, have not yet been made public.
The polar bear data are contradictory: contrary to predictions, several polar bear subpopulations (at least four of them) are indeed thriving despite much reduced summer sea ice. I have chosen to emphasis that good news, while Stirling and Derocher choose to emphasize the data that seem to fit their predictions. This is a classic conflict that happens all the time in science but presents no proof that I’m wrong or that the PragerU video is inherently ‘false’.
Susan, 18 May 2020
In short, it is indeed true that ‘Polar bears are thriving even where sea ice is diminishing.’ See also my 2018 opinion piece on the National Geographic ‘starving’ polar bear video in the Financial Post here. Climate Feedback reviewed that piece with statements by Steven Amstrup and Andrew Derocher, which I countered here, here, and here.
The review states: “There is no scientific evidence that the entire polar bear population has been growing, contrary to what this video claims.” In 2007 the global estimate used by the USGS in their analysis supporting the listing of polar bears as ‘threatened’ under the ESA was 24,500 (Amstrup et al. 2007) and the official IUCN estimate in 2015 (without the addition of several subpopulation estimates completed since then) was 26,000 (22,000-31,000)(Regehr et al. 2016; Wiig et al. 2015).
Do the math: 24,500 bears in 2007 vs. 26,000 bears in 2015 is an increase of 1,500 bears and indicate that overall population numbers have indeed grown by a small amount. More recent survey results add further to that total. I’ve pointed out this may well not be statistically significant increase but it is certainly not the decline that was predicted to occur when sea ice declined to present levels (Crockford 2017, 2019, 2020).
In addition to the thriving condition of Barents Sea bears discussed above (Aars 2018; Aars et al. 2017; Lippold et al. 2019), Chukchi Sea polar bears are also doing much better than they were in the 1980s despite much reduced summer sea ice. These results are documented in a number of peer-reviewed papers on the topic (ACSWG 2018; Regehr et al. 2018; Rode and Regehr 2010; Rode et al. 2013, 2014, 2018). Ringed and bearded seals are similarly thriving despite less summer ice (Crawford et al. 2015).
Despite these results, Stirling and colleagues conclude illogically that both Barents Sea and Chukchi Sea polar bear populations are merely “likely stable” (i.e. “OK”) rather than increasing. It is biologically implausible that both populations are merely holding their own: the Svalbard portion of the Barents Sea population increased by 42% between 2004 and 2015. However, this was dismissed as “statistically insignificant” even though the similarly “statistically insignificant” 17% decline in Southern Hudson Bay bears in 2018 was deemed valid and represented a ‘real’ decline – such games do not instill confidence that these researchers are presenting unbiased scientific results (Crockford 2019, 2020).
Stirling states in the review: “…a couple [subpopulations] are doing OK, such as Foxe Basin and Davis Straight, and one seems to be increasing (M’Clintock Channel).” As I mentioned above, he fails to mention the ‘increasing’ status of Kane Basin but his mention of M’Clintock Channel means we now we know why the report on the latest M’Clintock Channel population survey has not yet been released (see Crockford 2020): it obviously shows the population size has increased. More games.
I have previously addressed in detail the problems involved in the Southern Beaufort population estimate and those for Western and Southern Hudson Bay which are at odds with the picture presented by ClimateFeedback. See Crockford 2017, 2019, 2020.
Errors in the review:
1) “The global polar bear population is currently estimated to be approximately 20,000 – 25,000 bears, distributed among 19 subpopulations.” This is wrong: it’s an out-of-date estimate used in a paper co-authored by reviewer Derocher in 2013. The official global population estimate used by the IUCN (2015) and the IUCN Polar Bear Specialist Group (2018) is 22,000-31,000 (or 26,000 on average), see Regehr et al. 2016 and Wiig et al. 2015.
2) Reference 1 in the citation list: “Stirling et al. (2018)” should be Stirling et al. (2012)
3) Paragraph 3 of the review: “But as stated in Hunter et al. (2015)” should be Hunter et al. (2010).
Some related posts, with references:
Now 20 years with no trend in ice breakup dates for Western Hudson Bay polar bears [discusses the Lunn et al. 2016 paper cited in the Climate Feedback review]
[discussed the repeated starvation events that resulted from thick
spring ice conditions unique to the Southern Beaufort, which are now
falsely blamed on lack of summer ice.]
[discusses the polar bear subpopulation estimates that were not
included in the 2015 IUCN Red List assessment because they had not yet
[discusses Ian Stirling’s oft-repeated claim that the body condition of
polar bears in Western Hudson Bay has dropped and that cub survival
rates have “plummetted” – even though data supporting these claims have not been published – as I pointed out in my 2019 State of the Polar Bear Report (Crockford 2020)]
Chukchi Sea polar bears number almost 3000 according to new survey results update [reports the 2016 population estimate that replaces the old ‘guess’ of 2,000 bears used in the 2015 IUCN Red List assessment]
Polar bear specialists double-down on message of future starving bears [discusses the claim that Southern Beaufort Sea polar bears are starving due to declining summer sea ice]
Global polar bear abundance ‘best guess’ estimate is 39,000 (26,000-58,000) [discusses polar bear numbers at 2018 and why I think they are too low, see quote below].
“In 2014, the chairman of the IUCN Polar Bear Specialist Group (PBSG) emailed me to say that their global population size number ‘has never been an estimate of total abundance in a scientific sense, but simply a qualified guess given to satisfy public demand.’
In my new book, The Polar Bear Catastrophe That Never Happened, I contend that this situation will probably never change, so it’s time to stop holding out for a scientifically accurate global estimate and generate a reasonable and credible ‘best guess’. Recent surveys from several critical polar bear subpopulations have given us the information necessary to do this.
These new numbers make it possible to extrapolate from ‘known’ to ‘unknown’ subpopulations within so-called ‘sea ice ecoregions’ (defined in 2007 by polar bear scientists at the US Geological Survey, see Amstrup et al. 2007) as shown below, to update old estimates and generate new ones for never-studied areas.”
Aars, J. 2018. Population changes in polar bears: protected, but quickly losing habitat. Fram Forum Newsletter 2018. Fram Centre, Tromso. Download pdf here (32 mb).
Aars, J., Marques,T.A, Lone, K., Anderson, M., Wiig, Ø., Fløystad, I.M.B., Hagen, S.B. and Buckland, S.T. 2017. The number and distribution of polar bears in the western Barents Sea. Polar Research 36:1. 1374125. doi:10.1080/17518369.2017.1374125
AC SWG 2018. Chukchi-Alaska polar bear population demographic parameter estimation. Eric Regehr, Scientific Working Group (SWG. Report of the Proceedings of the 10th meeting of the Russian-American Commission on Polar Bears, 27-28 July 2018), pg. 5. Published 30 July 2018. US Fish and Wildlife Service. https://www.fws.gov/alaska/fisheries/mmm/polarbear/bilateral.htm pdf here.
Amstrup, S.C., Marcot, B.G. & Douglas, D.C. 2007. Forecasting the rangewide status of polar bears at selected times in the 21st century. US Geological Survey. Reston, VA. Pdf here
Amstrup, S.C., Marcot, B.G., Douglas, D.C. 2008. A Bayesian network modeling approach to forecasting the 21st century worldwide status of polar bears. Pgs. 213-268 in Arctic Sea Ice Decline: Observations, Projections, Mechanisms, and Implications, E.T. DeWeaver, C.M. Bitz, and L.B. Tremblay (eds.). Geophysical Monograph 180. American Geophysical Union, Washington, D.C. http://onlinelibrary.wiley.com/doi/10.1029/180GM14/summary and http://alaska.usgs.gov/science/biology/polar_bears/pubs.html
Atwood, T.C., Marcot, B.G., Douglas,D.C., Amstrup, S.C., Rode, K.D., Durner, G.M. and Bromaghin, J.F. 2015. Evaluating and ranking threats to the long-term persistence of polar bears. USGS Open-File Report 2014–1254. Pdf here.
Crawford, J.A., Quakenbush, L.T. & Citta, J.J. 2015. A comparison of ringed and bearded seal diet, condition and productivity between historical (1975–1984) and recent (2003–2012) periods in the Alaskan Bering and Chukchi seas. Progress in Oceanography 136:133-150.
Crockford, S.J. 2017. Testing the hypothesis that routine sea ice coverage of 3-5 mkm2 results in a greater than 30% decline in population size of polar bears (Ursus maritimus). PeerJ Preprints 2 March 2017. Doi: 10.7287/peerj.preprints.2737v3 Open access. https://doi.org/10.7287/peerj.preprints.2737v3
Crockford, S.J. 2020. State of the Polar Bear Report 2019. Global Warming Policy Foundation Report 39, London. PDF here.
Crockford, S.J. and Geist, V. 2018. Conservation Fiasco. Range Magazine, Winter 2017/2018, pg. 26-27. Pdf here.
Lippold, A., Bourgeon, S., Aars, J., Andersen, M., Polder, A., Lyche, J.L., Bytingsvik, J., Jenssen, B.M., Derocher, A.E., Welker, J.M. and Routti, H. 2019. Temporal trends of persistent organic pollutants in Barents Sea polar bears (Ursus maritimus) in relation to changes in feeding habits and body condition. Environmental Science and Technology 53(2):984-995.
Regehr, E.V., Laidre, K.L, Akçakaya, H.R., Amstrup, S.C., Atwood, T.C., Lunn, N.J., Obbard, M., Stern, H., Thiemann, G.W., & Wiig, Ø. 2016. Conservation status of polar bears (Ursus maritimus) in relation to projected sea-ice declines. Biology Letters 12: 20160556. http://rsbl.royalsocietypublishing.org/content/12/12/20160556
Rode, K. and Regehr, E.V. 2010. Polar bear research in the Chukchi and Bering Seas: A synopsis of 2010 field work. Unpublished report to the US Fish and Wildlife Service, Department of the Interior, Anchorage. pdf here.
Rode, K.D., Douglas, D., Durner, G., Derocher, A.E., Thiemann, G.W., and Budge, S. 2013. Variation in the response of an Arctic top predator experiencing habitat loss: feeding and reproductive ecology of two polar bear populations. Oral presentation by Karyn Rode, 28th Lowell Wakefield Fisheries Symposium, March 26-29. Anchorage, AK.
Rode, K.D., Regehr, E.V., Douglas, D., Durner, G., Derocher, A.E., Thiemann, G.W., and Budge, S. 2014. Variation in the response of an Arctic top predator experiencing habitat loss: feeding and reproductive ecology of two polar bear populations. Global Change Biology 20(1):76-88. http://onlinelibrary.wiley.com/doi/10.1111/gcb.12339/abstract
Rode, K. D., R. R. Wilson, D. C. Douglas, V. Muhlenbruch, T.C. Atwood, E. V. Regehr, E.S. Richardson, N.W. Pilfold, A.E. Derocher, G.M Durner, I. Stirling, S.C. Amstrup, M. S. Martin, A.M. Pagano, and K. Simac. 2018. Spring fasting behavior in a marine apex predator provides an index of ecosystem productivity. Global Change Biology http://onlinelibrary.wiley.com/doi/10.1111/gcb.13933/full
Wiig, Ø., Amstrup, S., Atwood, T., Laidre, K., Lunn, N., Obbard, M., et al. 2015. Ursus maritimus. The IUCN Red List of Threatened Species 2015: e.T22823A14871490. Available from http://www.iucnredlist.org/details/22823/0 [accessed Nov. 28, 2015]. See the supplement for population figures.