Tag Archives: Labrador

Claim of range-contraction of polar bears due to declines in summer sea ice doesn’t hold up

Have polar bears suffered a contraction of their historical range due to recent declines in summer sea ice? Buried in a recent journal article lies such a claim, one I can’t recall having seen before. That makes it worth close examination.

Figure 2. A drawing of polar bears on St. Matthew Island that accompanied the May 1, 1875 Harper’s Weekly Journal of Civilization article written by Henry Elliot. See here.

A drawing of polar bears on St. Matthew Island that accompanied the May 1, 1875 Harper’s Weekly Journal of Civilization article written by Henry Elliot. See here.

The assertion appears in the introduction of a recently published paper that got a lot of attention online (“Implications of the Circumpolar Genetic Structure of Polar Bears for Their Conservation in a Rapidly Warming Arctic” by Peacock and colleagues (2015), discussed previously here, news coverage here and here).

Here is how the authors put it:

There is already evidence of change in the contemporary distribution of polar bears. For example, polar bears, once common in Newfoundland [29], are now seen there only infrequently and in small numbers. Similarly, polar bears once regularly summered on St. Lawrence and St. Matthew islands in the Bering Sea [30–32]. Now they are irregularly observed in the Bering Sea and do not spend summers on St. Matthew Island. Although these changes in polar bear distribution may also have been related to overharvest, the recent reductions in the extent of sea-ice due would prevent current and regular use of these areas.[my emphasis]

There are three main reasons the claim doesn’t hold up to scrutiny:
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Labrador polar bears face a longer ice-free season than Hudson Bay bears, but do well

Pretty typical ice levels in both regions for this time of year – Davis Strait polar bears (especially those in Labrador) are still onshore while Hudson Bay bears (even those in the south) have their sea ice hunting platform back.

Davis Strait Hudson Bay freeze-up at Nov 25 2014_PolarBearScience

Funny thing is, the Davis Strait subpopulation may still be increasing despite a longer ice-free season than Western Hudson Bay. And bears in the south of that region – who spend the summer onshore in Labrador – have the longest ice-free season of all1 yet according to the latest survey they were even doing better than bears in northern Davis Strait.

That apparent paradox has an easy explanation – sea ice extent in late summer/early fall (length of the ice-free season) has much less of an impact on polar bear health and abundance than the state of the food supply in the spring. More seals in spring, polar bears do well; few seals in spring, polar bears starve.

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“Meltdown: Terror at the Top of the World” — new book exploits polar bear attack to sell fear of sea ice decline

The polar bear attack that was all over the news last summer is now an ebook about global warming. The Maine lawyer who was mauled by a bear while on a hiking trip to Labrador (and lived to tell the tale) has allowed his story to be co-opted by an activist journalist to promote fears of sea ice decline, polar bear extinction, and man-made global warming.

Melt-down_Terror at the Top of the World_Nov 12 2014 press release book cover

The press release issued yesterday by the news group that published the book and employs author Sabrina Shankman (InsideClimateNews), described it this way:

“A riveting new e-book about the battle between man, beast and Nature in a warming world. Called Meltdown: Terror at the Top of the World, the e-book tells the story of the hikers’ harrowing encounter with a polar bear; of the plight of the polar bear in general, facing starvation and extinction as the sea ice melts and its habitat disappears; and of the Arctic meltdown, the leading edge of man-made climate change.”

I have little doubt the man mauled by the bear was indeed terrified and that his companions were as well. However, that horror is exploited shamelessly in this book as a means to promote anxiety over the future survival of polar bears and instill panic over a prophesied Arctic “meltdown.”
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Summer sea ice melt and polar bear maternity dens

The yearly sea ice minimum extent is almost upon us, which has recently been the seasonal signal for excitable biologists and their activist groupies to resume their breathless rants about what sea ice loss could mean for polar bears.

Polar bear den_CreditUSFWS_labeled

Never mind that the summer minimum extent reached in September, no matter how low it goes, is pretty much irrelevant to polar bear health and survival. As I’ve discussed before, what’s really important is the presence of not-too-thick ice during the spring, so they can catch lots of young seals and put on lots of fat.

But to a lesser degree, the extent at mid-to-late summer is important because this is when pregnant females that prefer to make their maternity dens on shore are looking for good places to spend the winter.

So the topic for today is this: how much does the extent of ice at the height of summer dictate where polar bear females make their winter dens?
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Polar bear habitat: Spring 2014 in Eastern Canada was much better than 1969

It was a good year for polar bear habitat in the southern portions of Eastern Canada this spring – surprisingly, much better than it was in 1968 through 1970. And since spring conditions are what really matter to polar bears, this is good news indeed.

Environment Canada’s Canadian Ice Service recently published a nice little summary that has some rather eye-opening graphs. These describe the conditions for polar bears in the southern Davis Strait subpopulation – the one whose population size increased so dramatically between 1974 and 2007 despite lower-than-average ice extent in some years, even while their body condition declined (see here and here).

Environment Canada - Ice maps regions at July 26 2014

[Fitting post for the second anniversary of this blog, I think – more below1]

Note that I’ve added a “Blog Archive” page that lists all of my posts, easier to browse now that there are more than 200 of them.
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Of Labrador polar bears and sea ice way above normal off Newfoundland

A report yesterday of polar bears making a nuisance of themselves in Black Tickle, southern Labrador is the inspiration for this post. Those bears are part of the Davis Strait subpopulation (discussed previously here and here). Black Tickle is marked on the map below.

Black-tickle-map-Labrador

Arctic sea ice is tracking just at the edge of two standard deviations for this time of year but while extent is low in the Barents Sea, it is way up around the east coast of Canada.
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Thriving Foxe Basin and Davis Strait polar bears threaten nesting sea birds

UPDATE February 11, 2014. A reader (Kevin, at “Afton’s Waterfowl List”) has pointed out an error in Fig. 3, where I inadvertently labeled the bars on the upper graph as ending in 2011 instead of 2012 (the Pembroke graph ends at 2011. sigh..). I have corrected the figure and the text that refers to it, but do not believe it affects the overall conclusion. See for yourself. Thanks Kevin — and Alan for getting in touch!

Another round of press release inspired news stories emerged last week insisting that polar bear predation on ground-nesting birds during the summer ice-free period is evidence that they are nutritionally stressed by global warming.

A few weeks ago it was snow goose eggs in Western Hudson Bay – this time it’s thick-billed murre (Uria lomvia) and common eider (Somateria mollissima) eggs in Foxe Basin and Hudson Strait (e.g. see the story at Canada’s National Post and a short summary provided by Science [and it’s not even their paper!]). The source of the media attention this time is a newly-published paper by Samuel Iverson and colleagues (Iverson et al. 2014).

Figure 1. From Iverson et al. 2014 (their Fig.1), “map of the study area.” Most of the study sites are within the Foxe Basin polar bear subpopulation region (see Fig. 2 below), although the Ungava Peninsula (E), Ungava Bay (F) and Frobisher Bay (C) sites are in the Davis Strait subpopulation.

Figure 1. From Iverson et al. 2014 (their Fig.1), “map of the study area.” Most of the study sites are within the Foxe Basin polar bear subpopulation region (see Fig. 2 below), although the Ungava Peninsula (E), Ungava Bay (F) and Frobisher Bay (C) sites are in the Davis Strait subpopulation.

Polar bears have always preyed on ground-nesting sea bird and goose eggs while onshore (see Kelsey Eliasson’s take on the situation around Churchill, at his PolarBearAlley blog). The issue in this case is whether the increase in predation can be unquestionably blamed on reduced sea ice cover and nutritionally-stressed bears – that is, predation increases that correlate with year-to-year sea ice changes and bears in poor condition found consuming bird eggs.

As I did for the “polar bears eat more caribou and snow geese than they used to” press release, I refused to take the PR or the news stories at face value and went to the published paper and its supplemental data (it’s open access, see it for yourself here).

What I see in this paper is a spurious sea ice correlation and no data on the condition of the few bears observed consuming eggs. There is also no mention of the fact that polar bear numbers have increased in part of the study area (Davis Strait) or that bears in Foxe Basin and southern Davis Strait have been found to be in very good condition and reproducing well (Rode et al. 2014; Peacock et al. 2013). See my analysis below and judge for yourself.

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