Tag Archives: size

OK in the 80s but not now: ‘seeing more polar bears means there are more bears’

Wait for it, it will come: backlash from polar bear scientists for a statement by an Inuk bear safety guide in Labrador, reported by the CBC yesterday. The guide said there are more polar bears now than there were 25 years ago based on the fact that he is seeing more bears and that more bears mean more trouble with bears, including attacks on people. As I point out in my new book, The Polar Bear Catastrophe That Never Happened, only in the 1980s did biologists admit that seeing more bears meant there were actually more bears.

polar-bear-black-tickle_Edwin Clark submitted to CBC no date

This bear visited Black Tickle in Labrador a few years back. Edwin Clark photo.

It has not been OK anywhere else in the world over the last few years to suggest that seeing more bears meant more bears, whether you were Inuk or not – whether describing a subpopulation that’s officially ‘increasing’ or not.

According to biologist Andrew Derocher (University of Alberta), who famously said last year that ‘you can’t equate seeing more bears with there being more bears,’ all of the increased sightings and problems with bears in Labrador and Newfoundland are due to poor ice conditions. His colleague Ian Stirling (also University of Alberta) similarly puts the blame for increased polar bear/human conflicts and fatal attacks in Nunavut on a ‘shortage of ice‘. For polar bear specialists, it’s always ‘less ice‘, never ‘more bears.’

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Breaking: 2016 W. Hudson Bay polar bear survey shows the population is still stable

A just-released report on the most recent (2016) survey shows Western Hudson Bay polar bear numbers were still stable despite predictions that this subpopulation would be wiped out completely (reduced to zero) due to low Arctic sea ice.

Churchill_Polar_Bear_2004-11-15 Wikipedia

The authors of the report on the August 2016 aerial survey of the Western Hudson Bay polar bear subpopulation (Dyck et al. 2017) state clearly that the only trends they could find were that the number of adult males increased somewhat over 2011 estimates and the number of females either declined or remained stable. The overall population estimate was a bit lower (11% less) compared to the 2011 survey but the difference is not statistically significant. Therefore, the population status must be stable.

2011 estimate: 949 bears (using comparable data, range 618-1280), litter size 1.43

2016 estimate: 842 bears (using comparable data, range 562-1121), litter size 1.63

[cf. Foxe Basin [stable], from 2009-2010 survey (Stapleton et al. 2016) litter size was 1.54]

An 11% decline in WH numbers since 2011 is most definitely NOT the decline to ZERO (extirpation) we were told to expect with Arctic sea ice as low as it has been since 2007 (Crockford 2017, see list of annual minimum extents 2007-2017 here).

Note: The percentage decline from 2011 to 2016 for Western Hudson Bay polar bears is 11%, NOT 18% as claimed recently by Andrew Derocher on twitter: it is not appropriate to compare the official 2011 estimate of 1030 (Stapleton 2014) to the 2016 estimate of 842 because the methods used to generate the estimates were different (Dyck et al. 2017). The authors of the report state that the estimate for 2011 that’s comparable to 2016 is 949.

An 11% decline from 1030 would be 917 bears, a statistically insignificant decline that is also biologically insignificant and therefore, so slight as to indicate a stable population.

Predicted sea ice at 2050 and 2080 shown below (see Crockford 2017 for details):

Crockford 2017 sea ice graphic

Quotes, map, and table from the Dyck et al. 2017 report (pdf here) are copied below.

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Abrupt summer sea ice decline has not affected polar bear numbers as predicted

Yes, Arctic sea ice has declined since satellite records began in 1979 but polar bears have adjusted well to this change, especially to the abrupt decline to low summer sea ice levels that have been the norm since 2007.

Global pb population size sea ice 2017 July PolarBearScience

Some polar bear subpopulations have indeed spent more time on land in summer than in previous decades but this had little negative impact on health or survival and while polar bear attacks on humans appear to have increased in recent years (Wilder et al. 2017), the reasons for this are not clear: reduced summer sea ice is almost certainly not the causal factor (see previous post here).

Ultimately, there is little reason to accept as plausible the computer models (e.g. Atwood et al. 2016; Regehr et al. 2016) that suggest polar bear numbers will decline by 30% or more within a few decades: even the IUCN Red List assessment (Wiig et al. 2015) determined the probability of that happening was only 70%.

Arctic sea ice has never been a stable living platform (Crockford 2015): it shifts from season to season, year to year, and millennia to millennia. Without the ability to adapt to changing conditions, Arctic species like polar bears and their prey species (seals, walrus, beluga, narwhal) would not have survived the unimaginably extreme changes in ice extent and thickness that have occurred over the last 30,000 years, let alone the extremes of sea ice they endured in the last 200,000 years or so.

Some biologists continue to hawk doomsday scenarios for polar bears due to summer sea ice loss but the truth is that their previous predictions based on sea ice declines failed so miserably (e.g. Amstrup et al. 2007) that it’s impossible to take the new ones seriously — especially since the basic assumptions that caused the first predictions to fail have not been corrected, as I’ve stated in print (Crockford 2017:27):

In summary, recent research has shown that most bears are capable of surviving a summer fast of five months or so as long as they have fed sufficiently from late winter through spring, which appears to have taken place since 2007 despite marked declines in summer sea ice extent.

The assumption that summer sea ice is critical feeding habitat for polar bears is not supported.

Recent research shows that changes in summer ice extent generally matter much less than assumed in predictive polar bear survival models of the early 2000s as well as in recent models devised to replace them (Amstrup et al. 2010; Atwood et al. 2016a; Regehr et al. 2015; Regeher et al. 2016; Wiig et al. 2015), while variations in spring ice conditions matter more.

As a consequence, the evidence to date suggests that even if an ‘ice-free’ summer occurs sometime in the future ­ defined as sea ice extent of 1 million km2 or less (Jahn et al. 2016) ­ it is unlikely to have a devastating impact on polar bears or their prey. [my bold]

The abrupt drop in summer sea ice that occurred in 2007 was not predicted by experts to occur until mid-century yet the predicted decimation of polar bears worldwide expected under those conditions (a loss of 2/3 of the global total, to only about 6660-8325 bears) not only did not happen, it did not come even close to happening (Crockford 2017; see also my recent books, Polar Bear Facts & Myths, and Polar Bears: Outstanding Survivors of Climate Change, sidebar).

Instead, the global population grew from about 22,550 bears in 2005 to about 28,500 bears in 2015. And while this might not be a statistically significant increase (due to the very wide margins of error for polar bear estimates), it is absolutely not a decline.

The present reality is that low summer sea ice cover since 2007 has not caused polar bear numbers to decline and therefore, polar bears are not a species in trouble. This suggests that even if the Arctic should become briefly ice-free in summer in the future, polar bears are likely to be only minimally affected and not become threatened with extinction. Polar bears are outstanding survivors of climate change: recent research and their evolutionary history confirm this to be true.

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IUCN PBSG insists the 2015 Barents Sea polar bear count was not an increase

Similar to the spin on the 2013 Baffin Bay/Kane Basin polar bear population survey, the IUCN Polar Bear Specialist Group now insists the latest count of the Barents Sea subpopulation is not evidence of an increase in numbers since 2004, as the leader of the study announced in 2015.

Svalbard polar bear_Aars August 2015-NP058930_press release

This is Part 2 of the big surprises in the latest version of the polar bear status table published by the IUCN Polar Bear Specialist Group (PBSG) on 30 March 2017. See last post here regarding the PBSG population size estimates that no longer concur with the 2015 Red List assessment, including the global total — even though PBSG members wrote the report (Wiig et al. 2015, and its Supplement).

Here I want to focus on the results of subpopulation surveys that were made public after the 2015 Red List assessment was published, particularly the Barents Sea estimate.

While the 2013 Baffin Bay and Kane Basin estimates (SWG 2016) have been added to the new PBSG table, any suggestion that these might indicate population increases are strong discounted. Similarly, contrary to initial reports by the principal investigators of the survey, the PBSG insist that the Barents Sea population has not actually increased since 2004, which you may or many not find convincing.

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