Science, optimism, and the resilience of polar bears in an ever-changing Arctic

Optimism in conservation science — which the Smithsonian says we desperately need (Earth Optimism Summit 21-23 April 2017, apparently a huge success) — means it’s time to acknowledge and celebrate real conservation success stories. The Smithsonian folks probably won’t say it but I will — one of those successes is the recovery of polar bears.

Female with cub_Shutterstock_PolarBearScienceIt’s time to abandon the focus on prophesies of impending loss and accept that recovery of polar bears from the over-hunting of last century has continued despite a decade of low summer sea ice (Aars et al. 2017; Crockford 2017; Dyck et al. 2017; SWG 2016; York et al. 2016). Why not focus on the numerous images of fat, healthy bears rather than the anomalous starving ones?

It’s time to let go of imagined future catastrophes based on pessimistic failures of adaptation (Amstrup et al. 2007, 2008; Atwood et al. 2016; Stirling and Derocher 2012) and acknowledge that polar bears and Arctic seals, just like Pacific walrus (MacCracken et al. 2017; US Fish & Wildlife Service 2017), are resilient species with adaptive capabilities we are are only just beginning to comprehend (Crawford and Quakenbush 2013; Crawford et al. 2015; Escajeda et al. 2018; Rode et al. 2014; Stirling and Lunn 1997; Stirling et al. 1975a; Vibe 1965).

US Fish and Wildlife Service Press Release (4 October 2017), my bold:

“The U.S. Fish and Wildlife Service has found that the Pacific walrus does not require protection as threatened or endangered under the Endangered Species Act (ESA). The finding follows a comprehensive review and analysis of the best available scientific information concerning the species, as well as local and traditional ecological knowledge of Alaska Native peoples.

While walruses use sea ice for a variety of activities, including breeding, birthing, resting and avoiding predators, they have shown an ability to adapt to sea ice loss that was not foreseen when the Service last assessed the species in 2011.

“Our decision not to list the Pacific walrus under the Endangered Species Act at this time is based on a rigorous evaluation of the best available science, which indicates the population appears stable, and the species has demonstrated an ability to adapt to changing conditions,” said Fish and Wildlife Service Principal Deputy Director Greg Sheehan. “If future circumstances warrant or new information comes to light, we can and will re-evaluate the Pacific walrus for ESA protection. In the meantime, the species will continue to be federally protected under the Marine Mammal Protection Act.”

Polar bears, like Pacific walrus, will be protected in the US under the Marine Mammal Protection Act even if ESA protection is cancelled.

Giving up ESA protection would not throw conservation values and protection to the wind: it would just take away an unnecessary complexity that is not well supported by science (Crockford 2017; Crockford and Geist 2017). After all, the Marine Mammal Protection Act provided the support that allowed polar bear numbers to rebound after decades of over-hunting in the US.

It’s time to accept that the survival of these species through thousands of years of massive changes in sea ice habitat the like of which modern field biologists have never seen — is sound evidence of their innate adaptive ability (Cronin et al. 2014; Cronin and Cronin 2015).

Cronin and Cronin (2015) state (my bold):

“Despite the scale, frequency and rapidity of Quaternary climate changes, Arctic marine ecosystems associated with sea-ice habitats were extremely resilient, adapting through geographic range expansion into the Arctic during warm periods, and south into extra-Arctic regions during glacial periods. The stratigraphic record of the last 1.5 Ma indicates that no marine species’ extinction events occurred despite major climate oscillations.”

Sea ice may change in the future, as it has done in the past, but polar bears and their prey will almost certainly continue to exist.

In 2014, geneticist Matthew Cronin had this to say about a recent polar bear genetic study announced in a University of Alaska Fairbanks press release (pdf here) :

“The ramifications are that if the polar bear was an independent species for about 1 million years it survived previous cold and warm periods,” Cronin said. “This means the polar bear has been an independent lineage a long time through glacial and interglacial and warm periods.”

The last glacial period was at maximum extent about 22,000 years ago, and was preceded by a warm interglacial period about 130,000 years ago. Other warm and cold periods preceded that. Cronin thinks that if polar bears survived previous warm periods in which there was little or no arctic summer sea ice, this should be used in models predicting the species’ response to current climate change.

It seems logical that if polar bears survived previous warm, ice-free periods, they could survive another. This is of course speculation, but so is predicting they will not survive, as the proponents of the endangered species act listing of polar bears have done.” [my bold]

Instead of hand-wringing, perhaps we  should celebrate the fact that Arctic nations came together in 1973 to protect polar bears from a scourge that evolution could not have anticipated — the relentless slaughter by humans with guns (Honderich 1991; Stirling 2011), and that individual nations followed with their own protective legislation.

We have polar bears in abundance today because people in the 1960s and early 1970s saw that a different future was possible and did something about it.

It’s time to thank those dedicated people for their service (Ian Stirling included) and put the issue of polar bear survival to rest: polar bears have been saved. Optimism and curiousity should drive the conservation agenda forward (e.g. Swaisgood and Sheppard 2010), not the relentless pessimism that turns good news into personal attack (e.g. Harvey et al. 2017).

Maybe it’s time to turn to pure scientific research to help us understand how polar bears adapt so well to change. Maybe it would be better if we removed the need to justify Arctic science with conservation and managment objectives, including counting bears (an endeavour fraught with potential inaccuracies and wide margins of error anyway), and accept that polar bears can take care of themselves as long as hunting regulations are in place and enforced.

Let’s do some real science that tells us interesting things we didn’t know before, such as how so many female polar bears in Western Hudson Bay in the 1980s were able to produce triplet litters and wean their cubs at one and half years old when no other subpopulation under study at the time was able to do so (e.g. Ramsay and Stirling 1988; Stirling and Lunn 1997)?

Or why — exactly — sea ice in the Eastern Beaufort Sea gets too thick in early spring to support ringed seals, bearded seals, and polar bears (Bromaghin et al. 2015; Burns et al. 1975; Harwood et al. 2012; Ramseier et al. 1975; Smith 1987; Stirling 2002; Stirling and Lunn 1997; Stirling et al. 1975a, 1975b, 1980, 1981, 1982, 1985)?

Polar bears have been saved but we can still use some solid polar bear science.


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

Amstrup, S.C.,Marcot, B.G. and Douglas,D.C. 2007. Forecasting the rangewide status of polar bears at selected times in the 21st century. Administrative Report, US Geological Survey. Reston, Virginia. 8.8 MB pdf here [may no longer be available online]

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. and

Bromaghin, J.F., McDonald, T.L., Stirling, I., Derocher, A.E., Richardson, E.S., Rehehr, E.V., Douglas, D.C., Durner, G.M., Atwood, T. and Amstrup, S.C. 2015. Polar bear population dynamics in the southern Beaufort Sea during a period of sea ice decline. Ecological Applications 25(3):634-651.

Burns, J.J., Fay, F.H., and Shapiro, L.H. 1975. The relationships of marine mammal distributions, densities, and activities to sea ice conditions (Quarterly report for quarter ending September 30, 1975, projects #248 and 249). In Environmental Assessment of the Alaskan Continental Shelf, Principal Investigators’ Reports, July-September 1975, Volume 1. NOAA Environmental Research Laboratories, Boulder, Colorado. pp. 77-78. Pdf here.

Crawford, J. & Quakenbush, L. 2013. Ringed seals and climate change: early predictions versus recent observations in Alaska. Presentation by Justin Crawfort, 28th Lowell Wakefield Fisheries Symposium, March 26–29, Anchorage, AK. Available from [accessed June 7, 2013].

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. and Geist, V. 2018. Conservation Fiasco. Range Magazine, Winter 2017/2018, pg. 26-27. Pdf here.

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.

Cronin, T. M. and Cronin, M.A. 2015. Biological response to climate change in the Arctic Ocean: the view from the past. Arktos 1:1-18 [Open access]

Cronin, M.A., Rincon, G., Meredith, R.W., MacNeil, M.D., Islas-Trejo, A., Cánovas, A. and Medrano, J. F. 2014. Molecular phylogeny and SNP variation of polar bears (Ursus maritimus), brown bears (U. arctos), and black bears (U. americanus) derived from genome sequences. Journal of Heredity.

Dyck, M., Campbell, M., Lee, D., Boulanger, J. and Hedman, D. 2017. 2016 Aerial survey of the Western Hudson Bay polar bear subpopulation. Final report, Nunavut Department of Environment, Wildlife Research Section, Iglolik, NU.

Escajeda, E., Laidre, K.L., Born, E.W., Wiig, O, Atkinson, S., Dyck, M., Ferguson, S.H. and Lunn, N.J. 2017. Identifying shifts in maternity den phenology and habitat characteristics of polar bears (Ursus maritimus) in Baffin Bay and Kane Basin. Polar Biology 41:87-100.

Harwood, L.A., Smith, T.G., Melling, H., Alikamik, J. and Kingsley, M.C.S. 2012. Ringed seals and sea ice in Canada’s western Arctic: harvest-based monitoring 1992-2011. Arctic 65:377-390.

Honderich, J.E. 1991. Wildlife as a hazardous resource: an analysis of the historical interaction of humans and polar bears in the Canadian arctic. MA thesis, University of Waterloo, Ontario.

MacCracken, J.G., Beatty, W.S., Garlich-Miller, J.L., Kissling, M.L. and Snyder, J.A. 2017. Final species status assessment for the Pacific walrus (Odobenus rosmarus divergens). US Fish & Wildlife Service, Anchorage, AK.
USFWS Species Assessment Report for the Pacific Walrus (final), May 2017

Ramsay, M.A. and Stirling, I. 1988. Reproductive biology and ecology of female polar bears (Ursus maritimus). Journal of Zoology London 214:601-624.

Ramseier, R.O., Vant, M.R., Arsenault, L.D., Gray, L., Gray, R.B., and Chudobiak, W.J. 1975. Distribution of the ice thickness in the Beaufort Sea. Beaufort Sea Technical Report #30. Canada Dept. of Environment, Victoria, B.C. Available online.

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.

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. 2017. Spring fasting behavior in a marine apex predator provides an index of ecosystem productivity. Global Change Biology

Smith, T.G. 1987. The Ringed Seal, Phoca hispida, of the Canadian Western Arctic. Canadian Bulletin of Fisheries and Aquatic Sciences 216. Department of Fisheries and Oceans, Ottawa. Google Books link

Stein, R., Fahl, K., Schade, I., Manerung, A., Wassmuth, S., Niessen, F. and Nam, S-I. 2017. Holocene variability in sea ice cover, primary production, and Pacific-Water inflow and climate change in the Chukchi and East Siberian Seas (Arctic Ocean). Journal of Quaternary Science 32:362-379. DOI: 10.1002/jqs.2929

Stirling, I. 2011. Polar Bears: The Natural History of a Threatened Species. Fitzhenry & Whiteside, Markham.

Stirling, I. and Derocher, A.E. 2012. Effects of climate warming on polar bears: a review of the evidence. Global Change Biology  18:2694-2706. doi:10.1111/j.1365-2486.2012.02753.x

Stirling, I. and Lunn, N.J. 1997. Environmental fluctuations in arctic marine ecosystems as reflected by variability in reproduction of polar bears and ringed seals. In Ecology of Arctic Environments, Woodin, S.J. and Marquiss, M. (eds), pg. 167-181. Blackwell Science, UK.

Stirling, I., Andriashek, D., Latour, P.B. & Calvert, W. 1975a. Distribution and abundance of polar bears in the Eastern Beaufort Sea. Beaufort Sea Tech. Report #2, Dept. Environment, Victoria, B.C.

Stirling, I., Archibald, R. & DeMaster, D. 1975b. Distribution and abundance of seals in the Eastern Beaufort Sea. Beaufort Sea Tech. Report #1, Dept. Environment, Victoria, B.C.

Stirling, I, Cleator, H. & Smith, T.G. 1981. Marine mammals. Polynyas in the Canadian Arctic (eds I. Stirling & H. Cleator), pp. 45-58. Canadian Wildlife Service Occasional Paper No. 45. Ottawa.

Stirling, I, Kingsley, M. & Calvert, W. 1982. The distribution and abundance of seals in the eastern Beaufort Sea, 1974–79. Canadian Wildlife Service Occasional Paper 47. Edmonton.

Stirling, I., Schweinsburg, R.E., Kolenasky, G.B., Juniper, I., Robertson, R.J., and Luttich, S. 1980. Proceedings of the 7th meeting of the Polar Bear Specialists Group IUCN/SSC, 30 January-1 February, 1979, Copenhagen, Denmark. Gland, Switzerland and Cambridge UK, IUCN., pg. 45-53. pdf of except here.

Stirling, I., Schweinsburg, R.E., Kolenasky, G.B., Juniper, I., Robertson, R.J., Luttich, S. et al. 1985. Research on polar bears in Canada 1978-80. Polar Bears: Proceedings of the 8th meeting of the Polar Bear Specialists Group IUCN/SSC, Oslo, Norway, 15-19 January 1981. (ed Anonymous), pp. 71-98. IUCN, Gland, Switzerland.

Swaisgood, R.R. and Sheppard, J.K. 2010. The culture of conservation biologists: show me the hope! BioScience 60(8): 626-630. Open access.

SWG [Scientific Working Group to the Canada-Greenland Joint Commission on Polar Bear]. 2016. Re-Assessment of the Baffin Bay and Kane Basin Polar Bear Subpopulations: Final Report to the Canada-Greenland Joint Commission on Polar Bear. +636 pp.

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 [accessed Nov. 28, 2015]

US Fish and Wildlife Service. 2017. “Endangered and Threatened Wildlife and Plants; 12-Month Findings on Petitions to List 25 Species as Endangered or Threatened Species” [pdf, search for “walrus”]

Vibe, C. 1965. The polar bear in Greenland. In, Proceedings of the First International Scientific Meeting on the Polar Bear. Fairbanks, Alaska 6-10 September 1965, IUCN Polar Bear Specialist Group. University of Alaska International Conference Proceedings Series, No. 1. pg. 17-25. Washington, DC. Available here.

York, J., Dowsley, M., Cornwell, A., Kuc, M. and Taylor, M. 2016. Demographic and traditional knowledge perspectives on the current status of Canadian polar bear subpopulations. Ecology and Evolution 6(9):2897-2924. DOI: 10.1002/ece3.2030

Comments are closed.