Category Archives: Population

Polar bears at Kaktovik, Alaska not stranded due to retreating ice

Posted on September 30, 2013 | Comments Off on Polar bears at Kaktovik, Alaska not stranded due to retreating ice

“I’ve lived here all my life and there are more bears every year. I read stories about polar bears being on the brink of extinction because of global warming, look out of my window and start to laugh.” Tori Sims, Kaktovik (Mail on Sunday, Sept. 28, 2013).

As you can see, Kaktovik is in the news again. This tiny community sits on the edge of the Beaufort Sea, on Barter Island on the North Slope of Alaska (Fig. 1). It lies within the Southern Beaufort polar bear subpopulation, which has been classified as “declining” by the IUCN Polar Bear Specialist Group (Obbard et al. 2010).

The determination of “declining” was based on a small dip in population numbers between 2001 and 2006 (not statistically significant), plus a decline in body size and condition, and smaller litter sizes documented between 1986 and 2006 (Rode et al. 2010). A new population survey is underway.

Figure 1. Kaktovik, Alaska, from Google maps.

Figure 1. Kaktovik, Alaska, from Google maps. Click to enlarge.

There have been suggestions that bears become “stranded” along the Alaska coast near Kaktovik because of retreating sea ice, and that more bears present in this area in recent years are an indication that they are in trouble due to global warming.

I’ve compiled some quotes, maps, and links to stories, photos and videos about Kaktovik polar bears to show that this claim is false.

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Polar Bear Specialist Group meeting postponed until 2014

Posted on September 12, 2013 | Comments Off on Polar Bear Specialist Group meeting postponed until 2014

[Update October 14, 2013: correction regarding Davis Strait population estimate, noted below]

I heard via the grapevine that the IUCN Polar Bear Specialist Group (PBSG) meeting, tentatively slated to be held this July (Obbard et al. 2010), has been postponed until 2014. [That will be the 16th Working Meeting, as they are called]

Word has it that shifting the meeting forward will allow the group time to put together a new population estimate that will incorporate recent survey results.

So which subpopulations are slated to be updated?

Figure 1. Polar bear subpopulations defined by the Polar Bear Specialist Group (PBSG). Note that Baffin Bay, Davis Strait, Western Hudson Bay and Southern Hudson Bay are all similar in that they become ice-free by early fall (the September minimum) or before.

Polar bear subpopulations defined by the Polar Bear Specialist Group (PBSG). Courtesy the PBSG.

As far as I can determine, there are at least two that haven’t quite been finished: Baffin Bay and Southern Beaufort. The Baffin Bay survey was supposed to be completed this spring, so the numbers just need to be crunched. Southern Beaufort has a survey in progress, planned to continue through the fall of 2013.

Here are some comments on the 2012 Southern Beaufort field season (USFWS Newletter 2013:17):

“The number of polar bears observed in 2012 was high relative to similar surveys conducted over the past decade. During August and September surveys, the majority of bears were observed east of Prudhoe Bay, primarily near Kaktovik. Body condition appeared relatively normal for this time of year with most bears reported to be in average condition.” [my bold] [see previous post here re: Kaktovik bears]

There are new counts for Foxe Basin (estimated at ~2,580 bears, similar to the early 1990s estimate of ~2,200; Stapleton, Peacock and Garshelis 2012) and Western Hudson Bay (estimated at ~1,000 bears, similar to the 2004 estimate of ~935; Stapleton, Atkinson et al. 2012) based on aerial surveys. These numbers have not yet been incorporated into the global total, although the studies suggest both of those populations have been stable since the last survey.

CBC News (June 26, 2012):

“A study has found that the polar bear population in the Foxe Basin region of Nunavut is stable and the bears are in good health.

The territorial government did an aerial survey of the bear population in 2009 and 2010. The survey results show the population is about the same size as it was in 1990 – about 2,580 bears.” [my bold]

There is also the new population estimate for Davis Strait (Peacock et al. 2013) that needs to be incorporated into the global total – in this case, there has been an increase from the previous estimate (up from ~1,400 to ~2,158). [corrected Oct. 14 2013] The population increase for Davis Strait has already been incorporated into the current global estimate. The new numbers were available by 2009 (the time of the last PBSG meeting) but the peer-reviewed publications (with all of the pertinent details) were not produced until recently (2012-2013, discussed here and here).
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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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Baffin Bay polar bear status – waiting for the count

Posted on July 30, 2013 | Comments Off on Baffin Bay polar bear status – waiting for the count

Here’s a quick summary of the status of Baffin Bay polar bears, a subpopulation I’ve not previously discussed in detail. Nothing especially earth-shattering here, except perhaps to wonder about the involvement of the World Wildlife Fund (WWF) in a new helicopter survey of the region.

Baffin Bay (Fig. 1) is north of Davis Strait. It lies between western Greenland and Baffin Island in the eastern Arctic.

Unlike the other north/south neighbour-pair of Western/Southern Hudson Bay   (which I discussed previously), the sea ice history for Baffin Bay/Davis Strait is not as similar: Davis Strait bears have a much longer on-shore fast than Baffin Bay bears (see last post here). However, all four of these subpopulations have ‘seasonal sea ice’ – that is, the ice melts completely in late mid-to-late summer, forcing bears onshore for varying lengths of time until fall freeze-up.

Figure 1. The Baffin Bay subpopulation region lies north of Davis Strait (map on the left from Vongraven and Peacock 2011: Fig. 3) and management is shared between Canada (Nunavut) and Greenland. In total area, it covers 1.08 million km2 and its “suitable ice habitat in spring” (according to Taylor and Lee 1995) is 413,500 km,2 somewhat less than Davis Strait. The map on the right shows the sea ice extent at the end of March 2010 (NSIDC), the winter maximum.

Figure 1. The Baffin Bay subpopulation region lies north of Davis Strait (map on the left from Vongraven and Peacock 2011: Fig. 3) and management is shared between Canada (Nunavut) and Greenland. In total area, it covers 1.08 million km2 and its “suitable ice habitat in spring” (according to Taylor and Lee 1995) is 413,500 km2, somewhat less than Davis Strait. The map on the right shows the sea ice extent at the end of March 2010 (NSIDC), the winter maximum.

A peer-reviewed paper published last year (Rode et al. 2012) compared body condition vs. sea ice changes in Davis Strait and Baffin Bay (discussed here). But while that research contributed to an updated population estimate for Davis Strait (Peacock et al. 2013, discussed here), it did not do the same for Baffin Bay. This is likely because the body condition work in Baffin Bay was split between spring and fall, and it has already been determined that many Baffin Bay bears are offshore in the spring and not available for counting using shore-based methods.

That’s a shame, because the last population estimate was completed back in 1997 (Taylor et al. 2005) and it is now seriously out of date.

However, it appears the Government of Nunavut is currently in the process of surveying this region by helicopter, so a new population estimate should be available soon.

But this aspect of the survey might surprise you — a press release issued February 11, 2013 by WWF contained the following statement:

“Results from the above-noted surveys will be completed and shared beginning in April 2013.

WWF made contributions of $82,000 to the Government of the Northwest Territories and $111,000 to the Government of Nunavut via Environment Canada, towards the total costs of these surveys. These funds were raised through the Arctic Home campaign from engaged Canadians and matched by The Coca-Cola Company.”  [my bold]

So, of the hundreds of millions the WWF pulls in from donations, they passed along less than $100,000 [$96,500 plus an equal contribution by Coca-Cola) to offset “the total costs of the survey.”

We are not told what those total costs are, but I expect they run well over a million dollars for a multiyear/multi-region project like this, perhaps over two million. Which makes $96,500 rather a drop in the bucket. That might have paid for some of the jet fuel for the helicopters used for the survey, but probably not all of it.

Status details below.
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Southern Hudson Bay subpopulation status, farthest south of all polar bears

Posted on July 25, 2013 | Comments Off on Southern Hudson Bay subpopulation status, farthest south of all polar bears

“The Arctic” is a bit hard to define. While the Arctic Circle works as a good boundary for some purposes and the 100C isotherm for July for others, neither work for polar bears because several subpopulations live well south of these limits (Fig. 1).

In the east, Western Hudson Bay, Southern Hudson Bay and Davis Strait are all located well south of the Arctic Circle and the first two (and half of Davis Strait) are beyond the 100C July isotherm as well. In the western Arctic, the Chukchi Sea subpopulation is within the 100C July isotherm but at least half of its bears reside south of the Arctic Circle (Fig. 1) in the Bering Sea (see previous post here).

Unique amongst all of these is Southern Hudson Bay – all of its polar bears make maternity dens and/or spend the summer south of 600N.

Southern Hudson Bay (SH) bears live in the Canadian provinces of Ontario, while Western Hudson Bay (WH) bears reside in Manitoba and Nunavut. The two groups mix over the winter but appear to spend the summer/fall in their respective regions (Stirling et al. 2004). [See previous posts on Western Hudson Bay bears here, here, and here]

“Further south” in the Arctic usually means warmer, with open water present more weeks every summer, sea ice for fewer weeks over the winter. So, shouldn’t the bears of Southern Hudson Bay be already suffering more harm from global warming than virtually all other subpopulations, including those in Western Hudson Bay?

After all, Western Hudson Bay bears appear to have experienced a statistically significant decline in numbers, among other effects (Regehr et al. 2007; Stirling and Derocher 2012) — surely Southern Hudson Bay bears are doing worse?

You’d think so, but they aren’t.

Figure 1. Boundary limits for “the Arctic” (top map) such as the Arctic Circle (dashed line) or the 100C isotherm for July (solid red line) would not include several polar bear subpopulations that live south of these.

Figure 1. Boundary limits for “the Arctic” (top map) such as the Arctic Circle (dashed line) or the 100C isotherm for July (solid red line) would not include several polar bear subpopulations that live south of these.

UPDATED October 28, 2014: Reference added, Obbard et al. 2013 (aerial survey results).
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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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Guest post: How ‘science’ counts bears

Posted on July 3, 2013 | Comments Off on Guest post: How ‘science’ counts bears

This essay by Dr. Jim Steele, professor emeritus, San Francisco State University, is reblogged from a July 3 2013 post at WUWT post, with Dr. Steele’s permission. I am not a field biologist and have never done a mark-recapture study but Dr. Steele has. His perspective on the way polar bear biologists count bears and estimate survival in the Southern Beaufort is a perfect companion to yesterday’s post, a related post that I’ll put up later this week, and this one from December, among others. I’ve added links to the references cited in this essay where they are available, as is my custom. See the original post for Jim’s responses to comments and questions.

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Guest post by Jim Steele   “How ‘science’ counts bears”

The Inuit claim “it is the time of the most polar bears.” By synthesizing their community’s observations they have demonstrated a greater accuracy counting Bowhead whales and polar bears than the models of credentialed scientists. To estimate correctly, it takes a village. In contrast the “mark and recapture” study, which claimed the polar bears along South Beaufort Sea were victims of catastrophic global warming and threatened with extinction, relied on the subjective decisions of a handful of modelers.

In mark and recapture studies, the estimate of population abundance is skewed by the estimate of survival. For example, acknowledging the great uncertainty in his calculations of survival, in his earlier studies polar beat expert Steven Amstrup reported three different population estimates for bears along the South Beaufort Sea. If he assumed the adult bears had an 82% chance of surviving into the next year, the models calculated there were 1301 bears. If survivorship was 88%, the abundance climbed to 1776 bears. If he estimated survivorship at a more robust 94%, then polar bear abundance climbed to 2490.1 Thus depending on estimated survival rates, a mark-and-recapture study may conclude that the population has doubled, or that it has suddenly crashed.

Here are the simplified basics of estimating survival.

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Did polar bear numbers in E. Beaufort fluctuate each decade due to thick ice years?

Posted on July 2, 2013 | Comments Off on Did polar bear numbers in E. Beaufort fluctuate each decade due to thick ice years?

Now that we have a plausible explanation (previous post here) for why shorefast ice in the Eastern Beaufort got too thick for ringed seals every ten years or so, it’s time to talk about the effect that this recurring sea ice phenomenon might have had on polar bear population numbers.

We know from the reports of polar bear biologists that without fat young seals to eat in the spring, some bears in those thick-ice springs came close to starving and many mothers lost all or most of their cubs (Amstrup et al. 2006; Stirling 2002; Stirling and Lunn 1997; Stirling et al. 1980; Stirling et al. 2008). This presumably had some impact on population numbers – the question is: how bad was it?

None of the reports on the effects of the thick ice have given us any indication of how many polar bears might have died or lost their cubs. However, Ian Stirling and colleagues (Stirling et al. 2011) recently published a paper on the Northern Beaufort subpopulation that looked, at first glance, to have done just that.

You have to keep in mind that the geographic area in question – the Eastern Beaufort – is not an official polar bear subpopulation region – at least, not any more. As Fig. 1 below shows, the Eastern Beaufort was once its own, strictly Canadian region (or at least, a strictly Canadian research region) see previous post here), but management is now shared between two subpopulations and managed by two governments (Canada and the USA). About half of the bears of the “Eastern Beaufort” reside in the ‘Northern Beaufort’ subpopulation and the other half live in the ‘Southern Beaufort’ subpopulation.

Figure 1. Re-jigging of polar bear subpopulations now splits what used to be an entirely Canadian segment, called the “Eastern Beaufort” (map on the left, from Stirling and Lunn 1997), into “Southern Beaufort” (shared with the USA) and “Northern Beaufort,” with the Canada-USA border at 141 W (map on the right, from Stirling et al. 2011). Labels added for clarity. Most of the polar bears sampled for the Stirling et al. paper were captured along the west and south coasts of Banks Island, although a few were captured north of Banks Island in M’Clure Strait and in Amundsen Gulf to the southeast.

Figure 1. Re-jigging of polar bear subpopulations now splits what used to be an entirely a Canadian research segment, called the “Eastern Beaufort” (map on the left, from Stirling and Lunn 1997), into management regions called “Southern Beaufort” (shared with the USA) and “Northern Beaufort,” with the Canada-USA border at 141 W (map on the right, from Stirling et al. 2011, Fig. 1). Labels added. Most of the polar bears sampled for the Stirling et al. paper were captured along the west and south coasts of Banks Island, although a few were captured in M’Clure Strait and in Amundsen Gulf.

Despite the changing boundaries, ringed seals and polar bears in the Eastern Beaufort have been the focus of research since the early 1970s. In part, this is because the region has been targeted for oil exploration and studies on both species have been part of the associated ecological impact assessments (Stirling et al. 1993).

Getting back to the point, did Stirling et al. 2011 find fluctuations in polar bear numbers in the Northern Beaufort that might reflect the periodic bouts of thick spring ice in the Eastern Beaufort? Unfortunately, no — the data lack necessary precision. You’ll see why, I think, from the summary below.  Continue reading

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Sea ice, beluga whales, and polar bear densities in the Gulf of Boothia

Posted on June 21, 2013 | Comments Off on Sea ice, beluga whales, and polar bear densities in the Gulf of Boothia

As I discussed in my last post, the Gulf of Boothia subpopulation in the central Canadian Arctic has the highest density of polar bears anywhere in the world. The question is, why?

For example, is the sea ice in the Gulf of Boothia region so markedly different from its nearest subpopulation-neighbor, M’Clintock Channel (Fig. 1), that it accounts for the wide disparity in polar bear densities between the two? The differences, remember, are dramatic: Gulf of Boothia, 18.3 bears per 1000 km2 vs. M’Clintock Channel, 1.9. And while M’Clintock Channel may be low in part due to recent over-harvests (see footnote 1), even the density before over-harvests occurred in M’Clintock Channel were only 4.7, compared to 10.4 bears per 1000 km2 in Gulf of Boothia (see Table 1 in previous post).

Today, I’ll take a look at sea ice and ringed seal habitat in the Gulf of Boothia and M’Clintock Channel, as well as information from a study on polar bear diets, which together shine some light on why the Gulf of Boothia is such a great place for polar bears.

Figure 1. Map showing the side-by-side relationship of M’Clintock Channel and the Gulf of Boothia. From Barber and Iacozza (2004: Fig. 1).

Figure 1. Map showing the side-by-side relationship of M’Clintock Channel and the Gulf of Boothia. From Barber and Iacozza (2004: Fig. 1).

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Gulf of Boothia, unheralded Arctic utopia, has the highest density of polar bears worldwide

Posted on June 18, 2013 | Comments Off on Gulf of Boothia, unheralded Arctic utopia, has the highest density of polar bears worldwide

The issue of polar bear population density (# of bears per 1000 km2) came up a few posts ago, during my discussion of the new Davis Strait population study by Lily Peacock and colleagues (here). Since the various polar bear subpopulations across the Arctic are so different in size, calculating the density of bears in the various regions generates an interesting metric of how well the regional populations are doing relative to each other.

Almost 20 years ago, Taylor and Lee (1995) did just that: they determined the density of polar bears in the various Canadian subpopulations, as of the 1990s. Surprisingly, the ‘leader’ among those, by a wide margin, was one of the smallest in geographic area: the Gulf of Boothia. Located in the central Canadian Arctic (see Figs. 1 and 2 below), in the 1990s, tiny Gulf of Boothia supported a density of 10.4 polar bears per 1000 km2, the highest density of all regions examined.

Figure 1. The Gulf of Boothia (circled) is right in the middle of the Canadian Arctic. In terms of geographic area, it is one of the smallest of all 19 subpopulations worldwide: at only 170,000 km2, only the Norwegian Bay and Kane Basin subpopulation regions, also in Canada (just to the north of Gulf of Boothia), are smaller at 150,000 and 155,000 km2 respectively (Vongraven and Peacock 2011). The Gulf of Boothia supports the highest density of polar bears known.Modified from map of polar bear protected areas provided by Environment Canada.


Figure 1. The Gulf of Boothia (circled) is right in the middle of the Canadian Arctic. In terms of geographic area, it is one of the smallest of all 19 subpopulations worldwide: at only 170,000 km2, only the Norwegian Bay and Kane Basin subpopulation regions, also in Canada (just to the north of Gulf of Boothia), are smaller at 150,000 and 155,000 km2 respectively (Vongraven and Peacock 2011). The Gulf of Boothia supports the highest density of polar bears known. Modified from the map of polar bear protected areas provided by Environment Canada.

But this density value for Gulf of Boothia was based on the 1986 population estimate of 900 bears – what is the most current figure?

For that, we need an updated population assessment. That was done in 2000 and it generated an estimate of 1,592 ± 361 bears (Taylor et al. 2009).

Taylor et al. (2009:791) said this about their assessment:

“Our results suggest population size had increased steadily under a harvest regimen of approximately 40 bears/yr” and added, “Barber and Iacozza (2004) found no trends in Gulf of Boothia sea ice conditions or ringed seal habitat suitability indices in the interval 1980-2000.”

In other words, despite there being no trend in either sea ice conditions or habitat for seals – and a yearly harvest of 40 bears – polar bear numbers in the Gulf of Boothia increased significantly (by almost 700 bears) during the twenty years between 1980 and 2000. Even if the 1986 estimate of approximately 900 bears was somewhat less accurate than the more recent one, the fact that tiny Gulf of Boothia can support 1,592 bears is surely a remarkable feat.

Using this new population estimate and the same area of ‘available habitat’ used by Taylor and Lee in 1995, I calculated the most recent density at a spectacular 18.3 bears per 1000 km2! [note this is exactly what Peacock et al (2013) did to get their density value of 5.1 bears/1000 km2, discussed here.] But I didn’t update just Gulf of Boothia, I did them all.

The updated density values for Gulf of Boothia and several other Canadian subpopulations are listed in Table 1 below. Note that aside from Davis Strait, as far as I know these density figures have not been published elsewhere: you’re seeing them here for the first time.

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