Global population size estimates for polar bears clash with extinction predictions

How many polar bears are there in the world? This was the primary question the International Union for Conservation of Nature (IUCN) had for the newly-formed Polar Bear Specialist Group (PBSG) back in 1968. Assessing the species global population size was part of the group’s mandate ahead of the 1973 international treaty to protect polar bears from wanton overhunting. For decades, this was an important objective for the scientists that made up the group.

However, about 15 years ago that goal disappeared. I contend it was abandoned because it had become incompatible with the PBSG claim that polar bears are ‘Vulnerable’ to extinction due to human-caused global warming. The group now insists that global population estimates cannot be used to determine if numbers have gone up or down: a Catch-22 that prevents public and scientific scrutiny. This is why they push back so hard when anyone suggests that global polar bear numbers have increased.

In 2006, the conservation status of every other species in the world except the polar bear was assessed by the IUCN based on current conditions. The polar bear was the first to be classified as ‘Vulnerable’ to extinction based on predicted future risks alone and the PBSG appeared committed to making this status classification stick for the foreseeable future.

When the PBSG decided polar bears should remain listed as ‘Vulnerable’ on the IUCN Red List, an incentive to manipulate population estimates was created – whether through unintentional or deliberate bias.

Abundance estimates for individual subpopulations of any species should add up to a global total. In fact, the PBSG clearly did this in 2001 when the global estimate was given as 21,500-25,000 (average 23,250), the figure included in a table of minimum and maximum estimates for all subpopulations.

That practice was dropped a few years later in favour of a vague estimate range (e.g. 20,000-25,000) provided in the text of the report only. The PBSG say they made this change because they suddenly realized that adding up columns of subpopulation estimates made the global totals look more scientifically accurate than they really were. That’s apparently why, in 2005, the total of all subpopulation maximum estimates (which added up to almost 28,000), suddenly became ’25,000’ for the estimated global maximum.

I doubt it was a coincidence that this change was made the same year the PBSG recommended the IUCN declare the polar bear ‘Vulnerable’ based on future threats. Thereafter, no matter how much new survey data became available or how many subpopulations were declared ‘data deficient’, the total estimate remained the same.

However, by 2015 the rules of the IUCN for listing a species as ‘vulnerable’ to extinction based on future threats had changed. It then required a global, population-wide estimate that was the total of all subpopulation estimates. The PBSG was forced to provide an estimate for the Chukchi, Kara, and Laptev Seas, as well as East Greenland, which they had not done since 2005 (claiming they were all ‘data deficient’).

Rather than give up their bid to retain the ‘Vulnerable’ status for polar bears, they estimated the Chukchi Sea at 2,000 bears (a figure they had used in 2005 but later abandoned), the Kara Sea at 3,200 bears (based on a 2013 Russian study they otherwise refuse to acknowledge), the Laptev Sea at 1,000 (based on 1993 data abandoned in 2013) and 2,000 for East Greenland (the low end of an estimate of 2,000-4,000 used in 1993 and later abandoned).

The table below shows the PBSG assessment table for 2013, showing all of the above four subpopulations listed as ‘unknown’ (apologies for the poor quality but it is all they made available when they moved their assessments online).

It is obvious that the PBSG hated being forced to do this: for at least two years afterward, they refused to acknowledge the 2015 global total.

Nevertheless, the resulting global population estimate provided for polar bears was 26,000 based on a range of 22,000-31,000. Based on this assessment, there was considered to be a 71% chance that the 26,000 bears alive in 2015 (i.e. the global total) would decline to approximately 18,200 bears by the year 2050 (find this in the IUCN assessment supplement).

Obviously, the only way to determine whether that threshold is ever reached is via the global population total.

However, PBSG researchers still insist they cannot say whether polar bear numbers have gone up or down based on the global total, no matter how many new subpopulation surveys have been completed. They created this Catch-22 to prevent scrutiny and attack anyone who suggests that numbers may have increased.

The issue of whether polar bear numbers have gone up or down raised its ugly head again last week after Australian businesswoman and mining magnate Gina Rinehart gave a lecture to students at her former girl’s school and in the process mentioned polar bear numbers had increased over some unspecified period of time.  

The folks who ‘fact-check’ at the Australian Broadcasting Corporation (ABC) went to work.

In an essay published Tuesday 26 October 2021, the ABC fact checkers interviewed a number of experts from the PBSG who had a lot to say about the status of individual subpopulations but again insisted it was impossible to determine whether total polar bear numbers have gone up or down based on global totals. My initial response is here.

I contend that claim is demonstrably untrue: numbers have certainly risen since the 1960s and have probably risen since 2005 as well.

In my 2019 book, The Polar Bear Catastrophe That Never Happened, I documented the global estimates at 1960 that had been made by a number of very qualified polar bear researchers using the best available science at the time, which averaged about 10,000 bears (range 5,000-15,000). I contend this is a plausible and defensible ‘baseline’ figure: a starting point from which to assess future conservation efforts. This baseline estimate of 10,000 is consistent with international concerns that polar bear numbers had hit a critical low level by the late 1960s.

However, PBSG biologists obstinately refuse to acknowledge this or any other baseline figure, something no other marine mammal conservation group has ever done.

In 1986, PBSG member Ian Stirling stated that the maximum value might actually be as high as 40,000 if unstudied populations were given plausible estimates and added to the total. Oddly, he was not drummed out of the PBSG for saying so or publicly ridiculed by his colleagues.

By 1993, the most well-studied polar bear populations had more than doubled in size since the late 1960s and it was assumed unstudied populations had recovered as well.

As a consequence, the IUCN down-listed the polar bear in 1996 to ‘Least Concern’. I cannot emphasize enough that this was status change was based on population increases across the board.

Population survey results that have been published since 2015 indicate a number of subpopulations have continued to grow, although some of those increases have been deemed mathematically insignificant and therefore left out of recent PBSG data tables. One has to wonder, however, about the choice of statistical methods when even 42% and 36% increases are rendered immaterial. Why even bother doing the survey?

In contrast, statistically insignificant declines in subpopulation numbers were always reflected in the data, justified by various post hoc excuses to declare these ‘real’ declines (e.g. Western and Southern Hudson Bay).

As explained in my 2019 State of the Polar Bear Report, this game of mathematical shenanigans with population figures is a serious problem in the field. Virtually all polar bear biologists are also PBSG members: it is a closed shop with a monopoly on the data.

I contend the PBSG have been suppressing subpopulation and global population totals for years in an attempt to keep polar bears listed as ‘vulnerable’ by the IUCN and ‘threatened’ under the US Endangered Species Act (see my 2019 book for details). They simply cannot be trusted to provide honest figures when they are so obviously invested in a particular conservation status outcome.

I have therefore generated a plausible global total that uses their latest figures and where necessary, employs extrapolation to generate an estimate for subpopulations that have not yet been surveyed or have out-of-date survey data. For example, I extrapolated data from the 2015 survey of the Svalbard portion of the Barents Sea area to generate a more up-to-date figure for the entire Barents Sea subpopulation, based on information from a previous study that established there were 2.87 times as many bears in the Russian sector as in the Svalbard region. The PBSG oddly refused to do this despite the fact that something almost identical to this was done in 2016 to generate an estimate for the Chukchi Sea: a detailed survey of a small area was extrapolated to the entire region.

The results of my calculations are shown below for data available up to 2018 compared to the 1960 baseline (from page 110 of The Polar Bear Catastrophe That Never Happened). It shows a modest increase to about 39,000 (range 26,000-58,000). That mean figure is about the same as the maximum suggested by Ian Stirling in 1986 (i.e. 40,000) and therefore well within the realm of possibility. 

Even if the official PBSG estimates were merely cleaned up and updated, by the end of 2020 the global total had reached almost 30,000.

PBSG members have actively demanded the public pay attention to the plight of the polar bear for the last two decades with their scary predictions of impending extinction. However, the only valid metric of whether their predictions are on track to becoming true is the global population size, which the PBSG steadfastly refuses to appraise in earnest.

To distract from the resulting public criticism, former PBSG Chairman Dag Vongraven has recently admitted the group has felt the need to make even more dire predictions about the species’ future.

The problem with polar bear population size estimates is not that they represent a divide between science and public interests. The issue is that the PBSG has failed to fulfill its IUCN mandate in an honest and transparent manner and individual PBSG members gas-light the public whenever anyone suggests that polar bear numbers have increased rather than declined.

What they are doing is advocacy, not science. The IUCN should be ashamed it has allowed this to happen.

Comments are closed.