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
There is no evidence that slightly less winter sea ice than the average since 1979 has had any negative impact on polar bear health or survival: the difference is simply not biologically meaningful to Arctic animals.
Polar bear on winter sea ice around the yearly maximum in the Beaufort Sea, 2010 (March 21).
NASA’s 23 March 2018 announcement regarding the Arctic sea ice maximum this year:
“Sea ice in the Arctic grew to its annual maximum extent last week, and joined 2015, 2016 and 2017 as the four lowest maximum extents on record, according to scientists at the NASA-supported National Snow and Ice Data Center (NSIDC) and NASA.”
Except, what they don’t tell you is that 2006 had almost the same extent as 2018 and 2006 wasn’t far behind according to the official, averaged data presented at NSIDC’s Arctic Sea Ice News & Analysis:
Current conditions at the winter maximum (at 17 March 2018, from NSIDC Masie, extent measured at 14.7 mkm2, using software able to discern more ice than used for the figures in Table 1), shown below: Continue reading
Posted in Sea ice habitat
Tagged Arctic, climate change, global warming, health, maximum, melting, NASA, polar bear, sea ice, survival, warm, winter
A statement yesterday from Yegor Vereshchagin, wildlife conservation manager from Chukotka, Russia (Polar Bears Adjust to Climate Change, 20 February 2018) confirms that Chukchi Sea polar bears are currently doing extremely well.
Contrary to previous reports and predictions (e.g. Amstrup 2011; Amstrup et al. 2007, 2008; Durner et al. 2009), there appears to be no threats due to recent declines in summer sea ice (Rode and Regehr 2010; Rode et al. 2013, 2014, 2018) or from poaching.
Posted in Conservation Status, Population, Sea ice habitat
Tagged Chukchi Sea, Chukotka, climate change, poaching, polar bear, population size, Russia, sea ice, triplets
New Scientist has an article coming out next week takes a fairly reasoned approach to the polar bear conservation issue. It acknowledges that polar bear numbers have not declined in recent years even though summer sea ice dropped dramatically but goes on to perpetuate a number of myths that might not have happened if the author had done his homework or quizzed his other experts as thoroughly as he did me.
The survivors: is climate change really killing polar bears? Rapid global warming is said to be ringing the death knell for polar bears, by melthing their icy hunting grounds. But the reality is more complex. Fred Pearce, New Scientist 10 February 2018. Online now.
Posted in Conservation Status, Hybridization, Population, Sea ice habitat
Tagged climate change, conservation, extinction, global warming, grizzly, grolar, hungry, hybrid, Pearse, pizzly, polar bear, population size, sea ice, starving, survivors
The really significant content of a new paper being heavily-hyped by the media1 is what wasn’t said rather than what the authors discovered about metabolic rates and weight maintenance of a small sample of nine Southern Beaufort Sea bears in 2014 to 2016 (Pagano et al. 2018; Whiteman 2018).
This paper does not document starving or dying bears but merely found some (5/9) that lost weight when they should have been gaining, given that early April is the start of the ringed seal pupping season (Smith 1987) and the intensive spring feeding period for polar bears (Stirling et al. 1981).
The question is, why were Southern Beaufort Sea polar bears off Prudhoe Bay (see map of the study area below), still hunting and capturing only adult and subadult ringed seals from sea ice leads when newborn ringed seal pups and their mothers should have been plentiful and relatively easily available in their birth lairs on the sea ice (see below)?
“Using video collar data, we documented bears’ hunting behavior and foraging success. Bears used sit-and-wait tactics to hunt seals 90% of the time, and stalking comprised the remaining 10% of hunts (movies S1 to S4) (19). Bears that successfully killed and ate adult or subadult ringed seals either gained or maintained body mass, whereas bears that only scavenged or showed no evidence of eating lost mass.”
There was no discussion in the paper of ringed seal birth lairs, or sea ice conditions at the time of the study, but several mentions about what might happen in the future to sea ice and potential consequences for polar bears. The press release did the same.
However, as you’ll see by the sea ice thickness maps below, there may be good reason for the lack of ringed seal lairs, and a general lack of seals except at the nearshore lead that forms because of tidal action: the ice just a bit further offshore ice looks too thick for a good crop of ringed seals in all three years of the study. This is reminiscent of conditions that occurred with devastating results in the mid-1970s and mid-2000s (Burns et al. 1975; Cherry et al. 2009; Harwood et al. 2012, 2015; Pilfold et al. 2012; Stirling 2002, Stirling et al. 1987). Those events affected primarily bears in the eastern half of the Southern Beaufort and were almost certainly responsible for the recorded decline in SB bear numbers in the 2001-2010 survey (Bromaghin et al. 2015; Crockford 2017; Crockford and Geist 2018).
It seems very odd to me that Pagano and colleagues suggested no reasons for the unexpectedly poor showing of polar bear hunting success during their study except a bit of hand-waving about higher-than-we-thought metabolic rates in the bears. For years, I’ve worried that the inevitable next episodes of thick Southern Beaufort spring ice would cause problems for polar bears and seals but we wouldn’t know it because whatever effects were documented would be blamed on reduced summer ice: I suspect that time may have come.
Figure 1 from Pagano et al. 2018 cropped to show only the study area off Alaska.
Posted in Advocacy, Conservation Status, Sea ice habitat
Tagged Beaufort Sea, climate change, global warming, polar bear, sea ice, starving, struggling, survival, threatened, trouble, USGS, wasting, worse than we thought
In scanning comments generated by the recent flurry of internet interest in polar bears and blogs I noticed that a good many people, fed alarming media stories, are still convinced that polar bear numbers are declining rapidly when nothing could be further from the truth.
Posted in Advocacy, Population
Tagged climate change, estimates, facts, global warming, good news, observations, population size, science, sea ice, status