Sea ice is said to be “an essential habitat for polar bears” but that’s an overly simplistic advocacy meme as ridiculous as the “no sea ice, no polar bears” message with which the public is constantly bombarded. Polar bears require sea ice from late fall to late spring only: from early summer to mid-fall, sea ice is optional. Historical evidence of polar bears that spent 5 months on land during the summer of 1874 proves an extended stay ashore is a natural response of polar bears to natural summer ice retreat, not a consequence of recent human-caused global warming. Sea ice is a seasonal requirement for polar bears: it’s not necessary year round.
[This PBI newsletter from 2011 repeats this meme and Andrew Derocher’s recent tweet conveys a similar message (“Sea ice loss = habitat loss for polar bears”)]
As long as sea ice is available from late fall through late spring (December to early June) and accompanied by abundant seal prey (sometimes it isn’t, see Derocher and Stirling 1995; Stirling 2002; Stirling et al. 1981, 1982, 1984), polar bears can survive a complete or nearly complete fast from June to late November (and pregnant females from June to early April the following year). That’s the beauty of their Arctic adaptation: fat deposited in early spring allows polar bears to survive an extraordinary fast whether they spend the time on land or sea ice.
Young and very old bears, as well as sick and injured ones, are the exception: these bears often come ashore in poor condition and end up dying of starvation — as a much-publicized bear on Baffin Island who likely had a form of cancer did last summer (Crockford 2018). Competition with bigger, stronger bears means these bears can’t keep what they are able to kill and they are most often the bears who cause problems. Starvation is the leading natural cause of death for polar bears because if they cannot put on the fat they need in spring, they will not survive the low food months of summer and winter, whether they are on land or out on the sea ice (Amstrup 2003). Continue reading
Posted in Advocacy, Life History, Sea ice habitat
Tagged Arctic, climate change, essential, facts, global warming, habitat, onshore, polar bear, sea ice, sea ice day, summer, terrestral dens
According to the Guardian (9 July 2018), there is a “global heat wave” going on right now.
In Siberia, the heat is supposedly “completely unprecedented” and will surely (we are told) impact Arctic sea ice — the habitat of the iconic polar bear. Yet a comparison of previous years shows little to no impact on sea ice: there is more ice present than there was in 2007.
Said The Guardian:
“But though we cannot say definitively that the current heatwave is caused by carbon emissions, it fits the pattern of long-term changes that we call climate. It is part of a global phenomenon, even if not the most important part. The really significant change is happening in eastern Siberia at the moment, where a completely unprecedented heatwave is warming that Arctic coastline, with consequences that are unpredictable in detail but surely bad on a large scale.” [my bold]
The heat — which some folks admit they not only expect during this season called summer but anticipate with joy — has been around since late June, with several locales outside Siberia affected, including southern Ontario, Quebec, Los Angeles CA, Britan, many locations in the eastern USA, Europe.
With so many locations across the Northern Hemisphere experiencing very hot weather over the last few weeks (maybe record-breaking, maybe not), let’s take a look at what all that heat is doing to Arctic sea ice compared to previous years.
A brave young father from Arviat on the northwest coast of Hudson Bay was killed yesterday evening by a polar bear while trying to protect his children.
Aaron Gibbons, 31, was the nephew of Gordy Kidlapik, who follows this blog and my twitter account. Gordy has often sent me useful local information and perspectives from Arviat, which is in Nunavut (north of Churchill, Manitoba).
It was heartbreaking to hear this news firsthand from Gordy:
More below and to follow as further details emerge. My sincere condolences to Gordy and his family – what a horrific loss.
UPDATE: 4 July 2018 9:00 pm PT. See correction below regarding the last fatal WHB attack, which was in 1999 (Rankin Inlet), not 1983 as my original title read. My apologies but as you’ll see, the newspaper didn’t get it right either.
Posted in Polar bear attacks, Sea ice habitat
Tagged Arviat, attack, Churchill, climate change, fatality, global warming, mauling, polar bear, sea ice, western hudson bay
Last week’s media coverage made me realize that James Hansen’s testimony to a US Senate committee in 1988 provided well-timed answer to a vexatious problem facing polar bear biologist Ian Stirling. Thirty years ago, Stirling was struggling to understand why polar bear productivity in Western Hudson Bay had dropped. He was ripe for the suggestion from Hansen (and his follow-up paper) that human-caused global warming could be the explanation. An interview with Stirling and colleague Andrew Derocher published in 2016 helps connect the dots.
Many bears were in poor condition in the fall of 1983 (Calvert et al. 1986:19, 24; Ramsay and Stirling 1988). In general, the 1980s saw weights of bears decline and cub mortality increase, with a marked increase in the loss of whole litters over what had been documented in the 1960s and 1970s (Derocher and Stirling 1992, 1995).
Until Hansen and climate change came along, density-dependent effects (such as the number of bears out-pacing food supply) were seen as the most likely explanation. But sea ice decline blamed on human-caused global warming was suddenly a new possibility that Stirling soon embraced (Stirling and Derocher 1993). By the late 1990s, sea ice coverage on Hudson Bay had indeed declined but the correlation with polar bear productivity produced a weak trend that was not statistically significant (Stirling et al. 1999).
The 1999 Stirling paper did not provide scientific evidence to explain the 1980s decline in productivity as much as it presented a novel scapegoat to blame when a more plausible explanation could not be made.
Bottom line: Global warming could not have been the proximate cause of the productivity changes in WH polar bears documented during the 1980s but Stirling spent the next two and a half decades vigorously pushing climate change as the cause of all polar bear ills. Continue reading
Posted in Conservation Status, Life History, Population, Sea ice habitat
Tagged body condition, climate change, decline, density-dependent response, global warming, Hansen, natality, polar bear, productivity, sea ice, Stirling, survival
The activist lawyer primarily responsible for polar bears being listed as ‘threatened’ on the US Endangered Species List (ESA) in 2008 is frustrated that those efforts have not generated her preferred political action. Kassie Siegel also claims in another 10 years it will be too late to save polar bears from extinction — despite clear evidence to the contrary.
In an emotional rant over at The Hill with a predictably hysterical headline, Siegel perhaps reveals more than she should about her motivation (“Keeping fossil fuels in the ground is the only way to save polar bears ravaged by climate change,” 26 May 2018).
Posted in Advocacy, Conservation Status, Population, Sea ice habitat
Tagged activists, anniversary, CBD, climate change, ESA, global warming, polar bear, politics, sea ice, walrus
Sea ice habitat for polar bears has not become progressively worse each year during their season of critical feeding and mating, as some scaremongers often imply. It’s true that absolute extent of Arctic ice is lower this spring than it was in 1979. However, according to NSIDC Masie figures, polar bear habitat at mid-May registers about 12 million km2, just as it did in 2006 (although it is distributed a little differently); other data show spring extent has changed little since a major decline occurred in 1989, despite ever-rising CO2 levels.
In other words, there has been virtually no change in sea ice cover over the last 12 years, despite the fact that atmospheric CO2 has now surpassed 410 parts per million, a considerable and steady increase over levels in 2006 which were about 380 ppm (see below, from the Scripps Oceanographic Laboratory, included in the Washington Post story 3 May 2018):
Not only that, but if rising CO2 levels were responsible for the decline of sea ice and implied effects on polar bears since 1979 (when CO2 levels were around 340 ppm), why has spring ice extent been so variable since 1989 (when the first big decline occurred) but so little changed overall since then? See the NSIDC graph below for April:
This year on day 134 (14 May), global ice cover registered 12.3 mkm2:
In 2016 on the same day, the overall extent was much the same but there was more ice in the Chukchi and Bering Seas and less in the eastern Beaufort:
More close-up charts of different regions below for 2018 vs. 2016, showing more detail.
Posted in Conservation Status, Life History, Sea ice habitat
Tagged carbon dioxide, climate change, CO2, facts, feeding, global warming, mating, polar bear, polynya, sea ice, shore leads, spring
Polar bear specialists made global population numbers the focus of the world’s attention when they predicted a dramatic decline and possible extinction of the species. But now that the numbers have increased slightly rather than declined, the same scientists say global numbers are meaningless: the public should give those figures no credence and anyone who cites global population numbers should be mocked.
See the screen shot from a 2015 NBC news video above and another from the science journal NATURE in 2008 below (Courtland 2008):
Yet, below is a recent message from one of the world’s most vocal polar bear specialists, four years after a similar incident raised the public’s ire:
However, you can’t make a plausible prediction of future survival without an estimate of present population size: not even today’s worst journalists would buy it, nor should they.