Latest global polar bear abundance ‘best guess’ estimate is 39,000 (26,000-58,000)

It’s long past time for polar bear specialists to stop holding out for a scientifically accurate global estimate that will never be achieved and determine a reasonable and credible ‘best guess’. Since they have so far refused to do this, I have done it for them. My extrapolated estimate of 39,000 (range 26,000-58,000) at 2018 is not only plausible but scientifically defensible.

Polarbear1_wikimedia_Andreas Weith photo Svalbard sm

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.

UPDATE: I have made this a sticky post for a while: new posts will appear below.

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.

USGS polar bear_ecoregions_icedrift

Since the PBSG has so far refused to take this step, I took on the challenge. I contend that an estimate of about 39,000 (range 26,000-58,000) at 2018 is not only plausible but scientifically defensible. See the graph below from my new book:

Population size estimate graph chapter 10

Global polar bear population size estimates to 2018. From Chapter 10 of The Polar Bear Catastrophe That Never Happened (Crockford 2019).

This new estimate for 2018 is a modest 4-6 fold increase over the 10,000 or so bears that existed in the 1960s and after 25 years, a credible increase over the estimate of 25,000 that the PBSG offered in 1993 (Wiig et al. 1995).

However, my new estimate is much larger than the improbable figure of about 26,000 (range 22,000-31,000) offered by PGSG biologists in 2015 (Regehr et al. 2016; Wiig et al. 2015). The scary question is this: what do Arctic residents do if there are actually as many as 58,000?

See my new book (Crockford 2019) for the full rationale and references used to arrive at this figure (my scientific paper is Crockford 2017, citation below).

The bottom line: it is scientifically unacceptable for the PBSG to continue to refuse to provide an extrapolated ‘best guess’ global estimate for polar bears, given that the scientifically accurate estimate they crave is essentially unattainable. An estimate of about 39,000 (range 26,000-58,000) at 2018 is not only plausible but scientifically defensible.

References

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

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://peerj.com/preprints/2737/

Crockford, S.J. 2019. The Polar Bear Catastrophe That Never Happened. Global Warming Policy Foundation, London. Available in paperback and ebook formats.

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

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/

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.

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