In scanning comments generated by the recent flurry of internet interest in polar bears and blogs I noticed that a good many people, fed alarming media stories, are still convinced that polar bear numbers are declining rapidly when nothing could be further from the truth.
In some cases, the media have made a possible future problem sound like a current problem. In others, people are remembering data from 2010 or so, not realizing that the picture has changed — or they assume that a conservation status of ‘threatened’ or ‘vulnerable’ (e.g. Amstrup et al. 2007) must mean numbers are declining (because that’s true for virtually all species classified that way, except polar bears).
The sea ice situation hasn’t really improved or deteriorated since 2007 but the polar bear picture is much better: there is information on more subpopulations and studies show most are holding stable or increasing (Aars et al. 2017; Crockford 2017a, b; Crockford and Geist 2018; Dyck et al. 2017; Matishov et al. 2014; Obbard et al. 2015, 2016; Stapleton et al. 2014; SWG 2016; Regehr et al. 2016; Rode et al. 2017; Wiig et al. 2015; York et al. 2016).
For example, USFWS biologist Eric Regehr stated late last year that the Chukchi Sea subpopulation, that has lived with very low summer sea ice since 2007 (Regehr et al. 2016; Stein et al. 2017), “appears to be productive and healthy.”
In fact, as of March 2017 — for the first time in decades — the IUCN Polar Bear Specialist Group no longer assigns a trend to any subpopulation in their status table.
Decide for yourselves why they would do that, when — for the first time in decades (cf. Wiig et al. 1995:24) — only one subpopulation (SB, Southern Beaufort) is still considered declining by some even though the data are disputed 1 (see here, captured 12 Jan 2016 via Wayback Machine, and status at 2005 here, captured March 2009, pdf backups here for 2016, here for 2009, here for Feb 2017, and here for Jan 2018).
Bottom line: The global population increase since 2005 is probably not statistically significant but it is certainly not a decline: polar bear numbers are not falling.
Note: the “Status and Trends” Environment Canada map for polar bears (below) for 2014 is now out of date:
Footnote:
1. From the IUCN PBSG Status Table for Southern Beaufort, updated March 2017 (my bold), note that the “changing sea ice conditions” referred to included thick spring ice in 2004-2006 (said to have been similar in severity to well-documented 1974-1976 events) that negatively affected body condition and survival (Crockford 2017 a,b; Crockford and Geist 2018; Harwood et al. 2012; Stirling 2002; Stirling et al. 2008; ) but is not specified as such:
“Results from a mark-recapture study conducted from 2001-2006 in both the USA and Canada indicated that the SB subpopulation included 1,526 (95% CI = 1,211 – 1,841) polar bears in 2006 (Regehr et al. 2006). That study and others found that the survival and breeding of polar bears were negatively affected by changing sea ice conditions, and that population growth rate was strongly negative in years with long ice-free seasons, such as 2005 when Arctic sea ice extent reached a former record low (Hunter et al. 2010, Regehr et al. 2010).
The most recent analysis (covering the years 2001-2010) showed that survival estimates remained low through 2007 and increased through 2009, resulting in an abundance estimate of 907 (95% CI = 548 – 1,270) polar bears present in 2010 (Bromaghin et al. 2015).
However, it is important to note that here [sic] is the potential for un-modeled spatial heterogeneity in mark-recapture sampling, resulting from field crews being unable to sample the entire geographic reach of the population boundaries, which could bias both survival and abundance estimates. A recent Traditional Knowledge study from Canada concluded that the numbers of polar bears in regularly used hunting areas have remained relatively stable within living memory (Joint Secretariat 2015).”
References
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]
Crockford, S. 2017a. 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
Crockford, S. 2017b. Twenty Reasons Not to Worry About Polar Bears: an update. Global Warming Policy Foundation Briefing 28. Pdf here.
Crockford, S.J. and Geist, V. 2018. Conservation Fiasco. Range Magazine, Winter 2017/2018, pg. 26-27. Pdf here.
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. http://www.gov.nu.ca/environnement/information/wildlife-research-reports#polarbear
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. http://arctic.synergiesprairies.ca/arctic/index.php/arctic/article/view/4236
Matishov, G.G., Chelintsev, N.G., Goryaev, Yu. I., Makarevich, P.R. and Ishkulov, D.G. 2014. Assessment of the amount of polar bears (Ursus maritimus) on the basis of perennial vessel counts. Doklady Earth Sciences 458 (2):1312-1316. [paywalled]
http://link.springer.com/article/10.1134/S1028334X14100298
Obbard, M.E., Stapleton, S., Middel, K.R., Thibault, I., Brodeur, V. and Jutras, C. 2015. Estimating the abundance of the Southern Hudson Bay polar bear subpopulation with aerial surveys. Polar Biology 38:1713-1725.
Obbard, M.E., Cattet, M.R.I., Howe, E.J., Middel, K.R., Newton, E.J., Kolenosky, G.B., Abraham, K.F. and Greenwood, C.J. 2016. Trends in body condition in polar bears (Ursus maritimus) from the Southern Hudson Bay subpopulation in relation to changes in sea ice. Arctic Science 2(1):15-32. http://www.nrcresearchpress.com/doi/abs/10.1139/AS-2015-0027#.VvFtlXpUq50
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. 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 http://onlinelibrary.wiley.com/doi/10.1111/gcb.13933/full
Stapleton S., Atkinson, S., Hedman, D., and Garshelis, D. 2014. Revisiting Western Hudson Bay: using aerial surveys to update polar bear abundance in a sentinel population. Biological Conservation 170:38-47. http://www.sciencedirect.com/science/article/pii/S0006320713004618#
Stirling, I. 2002. Polar bears and seals in the eastern Beaufort Sea and Amundsen Gulf: a synthesis of population trends and ecological relationships over three decades. Arctic 55 (Suppl. 1):59-76. http://arctic.synergiesprairies.ca/arctic/index.php/arctic/issue/view/42
Stirling, I., Richardson, E., Thiemann, G.W. and Derocher, A.E. 2008. Unusual predation attempts of polar bears on ringed seals in the southern Beaufort Sea: possible significance of changing spring ice conditions. Arctic 61:14-22. http://arctic.synergiesprairies.ca/arctic/index.php/arctic/article/view/3/3
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 http://onlinelibrary.wiley.com/doi/10.1002/jqs.2929/abstract
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. http://www.gov.nu.ca/documents-publications/349
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]
Wiig, Ø., Born, E.W., and Garner, G.W. (eds.) 1995. Polar Bears: Proceedings of the 11th working meeting of the IUCN/SSC Polar Bear Specialists Group, 25-27 January, 1993, Copenhagen, Denmark. Gland, Switzerland and Cambridge UK, IUCN. http://pbsg.npolar.no/en/meetings/
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
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