Tag Archives: polar bear

Polar bear habitat update for October 31, 2013

Posted on November 1, 2013 | Comments Off on Polar bear habitat update for October 31, 2013

Here’s the ground-truth follow-up to my suggestion of what polar bear habitat would likely look like 6 weeks after the minimum extent was reached this year – which was looking then like it would mirror 2009.

You’ll find my discussion, posted on September 22, here. At that point (September 13), ice extent was 5.1 million square kilometers; now it is 9.1 million square kilometers (Fig.1).

Figure 1. Oct 30 2013 Maisie sea ice extent, 9.1 mkm2. This does not take thickness or concentration into account.

Figure 1. Oct 30 2013 Maisie sea ice extent, 9.1 mkm2. Click to enlarge.

Have a look at the maps below: Fig. 2 to see how ice extent at October 31st compares to ice extent at the end of October 2009, and Fig. 3 to see what ice concentrations looked like in the Canadian Arctic.

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Polar bear cannibalism and sea ice, the spring of 1976

Posted on October 30, 2013 | Comments Off on Polar bear cannibalism and sea ice, the spring of 1976

Remember Ian Stirling’s claim that late freeze up in Western Hudson Bay in 2009 was forcing polar bears to resort to cannibalism (here and here), with gut-wrenching images and video provided for the media? Or Steve Amstrup’s claim for a similar phenomenon in the Southern Beaufort in 2004?

I pointed out that Stirling’s claim was way overblown and that Amstrup’s incidents were almost certainly the result of heavy ice in the spring (not low ice in summer), similar to the heavy ice conditions and polar bear starvation documented in the same region back in 1974-1976.

It turns out that the heavy ice conditions documented in the Eastern Beaufort in the mid-1970s had much broader effects on polar bears and ringed seals than has been appreciated.
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Record sea ice loss in 2007 had no effect on polar bears, Chukchi study confirms

Posted on September 15, 2013 | Comments Off on Record sea ice loss in 2007 had no effect on polar bears, Chukchi study confirms

One aspect of the recently published study on Chukchi Sea polar bears (Rode et al.2014 [now in print] 2013; see here and here) has not been stressed enough: their finding that the differences in overall condition between bears in the Chukchi and Southern Beaufort Seas came down to disparities in spring feeding opportunities and therefore, the condition of spring sea ice.

The fact that spring — not summer — is the most critical period for polar bears is something I’ve pointed out before (see here and here, for example) but it’s worth repeating at this time of year, when all eyes are on the annual ice minimum. It is often treated as a given that the decline in extent of summer sea ice in the Arctic since 1979 has been detrimental to polar bears. However, this is an assumption that we can now say is not supported by scientific evidence (see summary of that evidence here).

The results published by Rode et al. (2014 2013) not only add further support to the conclusion that declines in summer sea ice have not harmed polar bears, but should put the matter to rest – unless new evidence to the contrary is produced.

Chukchi bears, the report tells us, had more food available in the spring than Southern Beaufort bears (see map below) and this was the primary reason that bears were doing very well in the Chukchi and not quite as well in the Southern Beaufort. And because the polar bears for this study were captured and measured in mid-March to early May, from 2008 to 2011, they reflect spring-time conditions for 2008-2011 as well as year-round conditions from 2007 through 2010.

This means that the annual low ice extent for 2007 (record-breaking at the time), in the fall before this study began, had no discernible negative effect on either Chukchi or Southern Beaufort polar bears – and neither did similarly low annual minimums in two of the three remaining years of the study (Fig 1).

Figure 1. Sea ice extent at August 27, 2007 – the lowest extent that year (downloaded September 15, 2013 from IARC-JAXA, Arctic Sea-ice Monitor). At the time, it was the lowest extent recorded since 1979 (2012 broke that record). This (2007) was the fall before the Rode & Regehr study on Chukchi/Southern Beaufort polar bears began (2008-2011). The ice was almost as low in September 2008 and 2010, while 2009 was more like 2013.

Figure 1. Sea ice extent at August 27, 2007 – the lowest extent that year (downloaded September 15, 2013 from IARC-JAXA, Arctic Sea-ice Monitor). At the time, it was the lowest extent recorded since 1979 (2012 broke that record). This (2007) was the fall before the Rode & Regehr study on Chukchi/Southern Beaufort polar bears began (2008-2011). The ice was almost as low in 2008 and 2010, while 2009 was more like 2013.

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Polar bears have not been harmed by sea ice declines in summer – the evidence

Posted on August 18, 2013 | Comments Off on Polar bears have not been harmed by sea ice declines in summer – the evidence

PB logo colouredThe polar bear biologists and professional activists of the IUCN Polar Bear Specialist Group (PBSG) continue to insist that since 1979 increasingly smaller amounts of Arctic sea ice left at the end of summer (the September ice minimum) have already caused harm to polar bears. They contend that global warming due to CO2 from fossil fuels (“climate warming” in their lexicon) is the cause of this decline in summer ice.

In a recent (2012) paper published in the journal Global Change Biology (“Effects of climate warming on polar bears: a review of the evidence”), long-time Canadian PBSG  members Ian Stirling and Andrew Derocher (both of University of Alberta) summarized their position this way:

“Climate warming is causing unidirectional changes to annual patterns of sea ice distribution, structure, and freeze-up. We summarize evidence that documents how loss of sea ice, the primary habitat of polar bears (Ursus maritimus), negatively affects their long-term survival”

I’ve spent the last year examining their evidence of on-going harm, but in addition, I’ve looked at the evidence (much of it not mentioned in the Stirling and Derocher paper1) that polar bears have either not been harmed by less sea ice in summer or have thrived in spite of it.

This is a summary of my findings. I’ve provided links to my original essays on individual topics, which are fully referenced and illustrated. You are encouraged to consult them for complete details. This synopsis (pdf with links preserved, updated; pdf with links as footnotes, updated) complements and updates a previous summary, “Ten good reasons not to worry about polar bears” (pdf with links preserved; pdf with a foreword by Dr. Matt Ridley, with links as footnotes).

Update 8 September 2013: to include links to my post on the recently published Chukchi population report; updated pdfs have been added above.

Update 22 January 2014: added figure comparing March vs. September sea ice extent using the same scale, from NOAA’s “2014 Arctic Report Card,” discussed here.
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Global population of polar bears has increased by 2,650-5,700 since 2001

Posted on July 15, 2013 | Comments Off on Global population of polar bears has increased by 2,650-5,700 since 2001

The official population estimates generated by the IUCN Polar Bear Specialist Group (PBSG) give the impression that the global total of polar bears has not changed appreciably since 2001:

2001 PBSG report                  21,500-25,000

2005 PBSG report                  20,000-25,000

2009 PBSG report                  20,000-25,000

2013 PBSG website                20,000-25,000

2015 IUCN Red List              22,000-31,000 [see latest update note]

However, some accounting changes were done between 2001 and 2009 (the latest report available) that mean a net increase in numbers had to have taken place (see summary map below and previous post here. Note this is a different issue than the misleading PBSG website graphic discussed here).

And while it is true that population “estimates” are just that — rather broad estimates rather than precise counts — it is also true that nowhere do the PBSG explain how these dropped figures and other adjustments were accounted for in the estimated totals. 

The simple details of these changes are laid out below, in as few words as I could manage, to help you understand how this was done and the magnitude of the effect. It’s a short read — see what you think.

UPDATE 15 May 2016: In late November 2015, the IUCN Red List of Threatened Species published a new assessment for polar bears that estimated the global population at 22,000-31,000 and stated the trend was ‘Unknown’. See details here and here – which includes links to the official report and the press release. Sorry for the delay in updating this post.

UPDATE 31 May 2015: See the latest population numbers here.

UPDATE 5 December 2014: Links to more recent posts relevant to this issue added below. [including this one: Status of Canadian polar bear populations has been changed – more good news October 28, 2014

UPDATE February 14, 2014 — a new status table has been released, see new post here 

UPDATE February 18, 2014 — see graphs of the 1981-2013 estimates here.

Polar bear subpopulations as defined by the PBSG: Top, in the 2001 report; Bottom, 2009 report. Map courtesy PBSG, with a few labels added and the subpopulations identified where “accounting” changes or adjustments to estimates took place.SB, Southern Beaufort; NB, Northern Beaufort; VM, Viscount Melville; MC, M’Clintock Channel; LS, Lancaster Sound; GB, Gulf of Boothia; NW, Norwegian Bay; KB, Kane Basin; WH, Western Hudson Bay. Click to enlarge.

Polar bear subpopulations as defined by the PBSG: Top, in the 2001 report; Bottom, 2009 report. Map courtesy PBSG, with a few labels added and the subpopulations identified where “accounting” changes or adjustments to estimates took place.
SB, Southern Beaufort; NB, Northern Beaufort; VM, Viscount Melville; MC, M’Clintock Channel; LS, Lancaster Sound; GB, Gulf of Boothia; NW, Norwegian Bay; KB, Kane Basin; WH, Western Hudson Bay. Click to enlarge.

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