New evidence has come to light that mark-recapture field work used to calculate a new population estimate for Southern Beaufort polar bears did not conclude in 2010 as implied in a widely-publicized paper last month but continued until 2013.
As I discussed previously, last month’s widely-hyped paper (Bromaghin et al. 2015
in press) – which reported a decline of ~40% between 2004 and 2010 (based on spring mark-recapture work) – was contradicted by fall survey counts that suggested strongly a population rebound would have been apparent if the mark-recapture work had continued another two years.
A new paper by Karyn Rode and colleagues (which includes Bromaghin and others (e.g. Amstrup) from the previous paper), summarized in a USGS press release issued on Monday and published online Tuesday, utilized comprehensive data collected during mark-recapture work carried out in spring from 1982 to 2013 in the Southern Beaufort Sea.
This new paper used the same kind of comprehensive data as Bromaghin and colleagues – from the same season, in the same region – to assess potentially negative effects of the mark-recapture research method itself, up to 2012 and beyond.
More on the Rode et al. conclusions later1 – for the moment, what is important is that the work described in the paper confirms that spring mark-recapture work on polar bears in the Southern Beaufort continued beyond 2010. Bromaghin and colleagues didn’t end their mark-recapture work prematurely — they actually left data collected in 2011 and 2012 out of their population estimate analysis when they had to have known the population had not finished rebounding from the 2004-2006 decline.
As to why they might have done such a thing, I’ve discussed previously that IUCN Polar Bear Specialist Group (PBSG) biologists have until June 2015 to come up with projected population trends that meet the new strict standards set by the IUCN for its Red List status of ‘vulnerable.’
The model used by the US Fish and Wildlife Service to list polar bears as ‘threatened’ in 2008, developed primarily by Steven Amstrup, has been heavily criticized by IUCN model experts. The PBSG has been told, in no uncertain terms, that stringent scientific methods are now required by the IUCN to base a status assessment on future threats. [Previously, they required hardly any scientific justification at all]
If the PBSG cannot develop, before next June, a scientifically supportable method of predicting a polar bear population decline of 30% or more within the next 30-36 years, polar bears will be demoted to a conservation status of ‘least concern’ or even ‘data deficient’ on the IUCN 2015 Red List, a result that is clearly unacceptable to the PBSG.
It appears pretty clear to me that the Southern Beaufort abundance study by USGS modelers and a number of prominent PBSG biologists, released with so much fanfare last month, was deliberately truncated to create an anomalously low population estimate and an exaggerated declining trend in an effort to ensure a desired result.
You might see it differently. But I suggest that if there was a reasonable explanation for truncating the end date for the study at 2010 when two additional years of data were available, the authors should have said so.2 If there was a valid reason for ignoring the data from 2011 and 2012, it should have been included in the original paper, in the press release and co-authors should have mentioned it in media interviews.
I can only conclude that PBSG-member biologists involved in the IUCN assessment are scrambling to justify keeping polar bears listed as ‘vulnerable’ on the next Red List and are willing to cut massive scientific corners to ensure that outcome.
Both papers One of the papers are paywalled, making the details they contain inaccessible to the general public. [UPDATE: the in-print version of the Bromaghin paper is Open Access, see below] However, in general, a quick email to the author with a simple request for a pdf copy should get you one. An alternative is to drop me a quick note (“Contact Us” page) and I’ll pass along a copy.
Footnote 2. The fact that the 2011-2013 data was collected in the Alaska portion of the region only should not have been a deterrent, since the models used in Bromaghin et al. had a way of accounting for data collected by different agencies at different times.
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
2014 in press. Polar bear population dynamics in the southern Beaufort Sea during a period of sea ice decline. Ecological Applications 25(3):634-651. http://www.esajournals.org/doi/abs/10.1890/14-1129.1 Open Access.
Rode, K. D., Pagano, A.M., Bromaghin, J.F., Atwood, T.C., Durner, G.M. and Simac K.S. 2014.
in press. Effects of capturing and collaring on polar bears: Findings from long-term research on the southern Beaufort population. Wildlife Research 41(4):311-322. [paywalled]
http://www.publish.csiro.au/nid/144/paper/WR13225.htm Supplementary Info: 10.1071/WR13225_AC Pdf here.