Polar bear population numbers are for kids, says specialist Andrew Derocher

Polar bear specialists made global population numbers the focus of the world’s attention when they predicted a dramatic decline and possible extinction of the species. But now that the numbers have increased slightly rather than declined, the same scientists say global numbers are meaningless: the public should give those figures no credence and anyone who cites global population numbers should be mocked.

NBC 2015_3 there will soon be a big decline in polar bear numbers snap

See the screen shot from a 2015 NBC news video above and another from the science journal NATURE in 2008 below (Courtland 2008):

Courtland 2008 headline

Yet, below is a recent message from one of the world’s most vocal polar bear specialists, four years after a similar incident raised the public’s ire:

Derocher tweet 2018 Feb 28 quote

However, you can’t make a plausible prediction of future survival without an estimate of present population size: not even today’s worst journalists would buy it, nor should they.

Here is Steven Amstrup on June 8, 2014 to his PBSG colleagues (obtained via FOI, see details here) regarding Vongraven’s email to me about population estimates:

Amstrup 2014 June re Vongravens unfortunate remark about population estimates

[“One thing Dag did say in his email to her [Crockford] that is somewhat problematic. He suggested that part of the reason PBSG [Polar Bear Specialist Group] provides these rough estimates is to meet public pressure. That is an unfortunate statement….”]

What Dag Vongraven actually said to me (via email) was that population estimates were only a “qualified guess given to satisfy public demand.” That didn’t go over well with the public (“The Politics of Polar Bears”).

I’m sure Derocher’s colleagues are thrilled with his similar interpretation of those estimates, stated not just on twitter but again in an early March interview with an online fact-checking outfit.  I made this statement in a Financial Post op-ed (27 February 2018):

“Although the extent of the summer sea ice after 2006 dropped abruptly to levels not expected until 2050, the predicted 67-per-cent decline in polar bear numbers simply didn’t happen. Rather, global polar bear numbers have been stable or slightly improved.”

To which Andrew Derocher responded, via ClimateFeedback (2 March 2018):

“The statement about global polar bear numbers is absolutely unfounded. It is a contrived statement using population estimates provided so that children (or the general public) could give a number of polar bears in the world for school reports and the like.”

[See my responses to the ClimateFeedback statements here and here from last month]

Polar bear specialists and their use of global estimates

The global total of 22,000-31,000 was the number used by members of the Polar Bear Specialist Group so that the IUCN would allow polar bears to keep their ‘vulnerable’ status. Wiig et al. (2015) is the document supporting the 2015 IUCN Red List assessment for polar bears as ‘vulnerable’ to extinction and their Supplementary document (pdf here) included a table of the subpopulation estimates (Table 3) that together totaled 26,485.

These numbers were used in their model of predicted polar bear decline based on predicted habitat loss, with no mention that the total was only meant for school children. In fact, the IUCN insisted such estimates be used (see Minutes of the 17th meeting of the IUCN Polar Bear Specialist Group 2014: 16, pdf here).

Regehr et al. 2016 is the peer-reviewed version of Wiig et al. (2015) and the authors state in their introduction: “The global population of approximately 26 000 polar bears is divided into 19 subpopulations.” There is no mention that this number is considered unscientific.

And back in the mid-2000s, the US Geological Survey used an estimate of 24,500 in their report, which also happened to be the total of their “ecoregion” population sizes, in their projected the future of polar bears to the end of the 21st century (Amstrup et al. (2007: Table 6).

Amstrup et al 2011 fig 1 ecoregions_lg

See map above from Amstrup 2011, which includes population estimates for the four sea ice ecoregions used to assess polar bear health and survival in 2007, used to support the US Fish and Wildlife decision to classify polar bears as ‘threatened’ on the Endangered Species List in 2008.

Have these researchers forgotten that the 1973 international treaty that spawned the formation of the IUCN Polar Bear Specialist Group (PBSG) was tasked not just with coordinating the research necessary for assessing polar bear health but with establishing a global population size (Anonymous 1968)?

It is clear that polar bear specialists use global and subpopulation estimates for modeling purposes upon which conservation assessments are based but at other times claim these are scientifically invalid. However, they can’t have it both ways: if the subpopulation estimates are scientific enough for making predictions, the total of those estimates must be good enough for assessing the validity of those predictions.

The public now have an intense interest in knowing the global population size of polar bears: that is not my doing but the result of polar bear specialists’ relentless message that declining sea ice is causing global polar bear numbers to decline. How else will the public know if the predicted catastrophe has happened if no one is permitted to mention global numbers without ridicule?

References

Amstrup, S.C. 2011. Polar bears and climate change: certainties, uncertainties, and hope in a warming world. In: R.T.Watson, T.J. Cade, M. Fuller, G. Hunt and E. Potapov (eds.), Gyrfalcons and Ptarmigan in a Changing World, Volume 1. The Peregrine Fund, Boise, Idaho.

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

Anonymous. 1968. Polar Bears: Proceedings of the 1st Working Meeting of Polar Bear Specialists, organized by IUCN at Morges, Switzerland, 29-31 January 1968. IUCN Bulletin, April/June 1968, Vol. 2, No. 7:54-56 (and reprinted in the 1970 Proceedings, pg. 89-91) http://pbsg.npolar.no/en/meetings/

Courtland, R. 2008. Polar bear numbers set to fall. Nature 453:432-433.

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. 2018. State of the Polar Bear Report 2017. Global Warming Policy Foundation Report #29. London. pdf here.

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., Amstrup, S., Atwood, T., Laidre, K., Lunn, N., Obbard, M., Regehr, E. & Thiemann, G. 2015. Ursus maritimus. The IUCN Red List of Threatened Species 2015: e.T22823A14871490. http://www.iucnredlist.org/details/22823/0

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