What’s a good analogy for sea ice as essential polar bear habitat? Biologist Andrew Derocher claims that the soil in a forest is appropriate, because without the soil you can’t have the forest ecosystem. However, that’s a specious comparison because the amount of soil in a forest does not change markedly with the seasons the way that Arctic sea ice does.
A much better analogy is a big pond that dries up a bit every summer. The amount of habitat available to sustain aquatic plants, amphibians and insects is reduced in the dry season but many species have special adaptations for surviving reduced water availability. For the rest of the year, however, the pond provides an abundant and non-limiting habitat for all the creatures and plants that live there.
Posted in Advocacy, Life History, Sea ice habitat
Tagged analogy, ecosystem, extinction, forest, habitat, Interglacials, polar bears, resilience, sea ice, wetlands
The simple fact is that if polar bear experts had been right about the threat to polar bears from the loss of summer sea ice in the Arctic, there would be no polar bears in Churchill this fall. No bears for tourists to photograph, none for biologists to study, and certainly none for the BBC to film for an upcoming three-part TV special called “Arctic Live.”
The low-ice future that biologists said would doom polar bears to extinction by 2050 has already happened in 8 out of the last 10 years. The sea ice future has been realized.
Polar bears have experienced those supposedly deadly low-ice summers for almost a decade but the global population did not drop by 2/3 as predicted and not a single one of the ten subpopulations predicted to be extirpated under those conditions has been wiped out.
How much more wrong can you be than that? Will the BBC mention this conundrum in their show? Will the polar bear experts they consult share this fact with viewers? We’ll all have to watch and see [show times and summaries of each program here, 1-3 November] but here are some background facts that might enhance your viewing experience.
UPDATE: Sea ice condition of Hudson Bay at 1 November 2016 below from the Canadian Ice Service (some slushy ice looks to be forming along the coast north of Churchill – this is how freeze-up starts). See the animation for the last 10 days here:
Posted in Population, Sea ice habitat
Tagged Arctic Live, BBC, Churchill, extinction, extirpation, facts, future, minimum, observations, polar bear, predictions, resilience, sea ice, September, survival, threatened
A quiet year for problems in the polar bear capital of the world (Churchill, Manitoba) so far – despite this year tying for the second-lowest minimum since 1979 – and the ice is growing fast. In fact, Arctic ice growth in the second half of September was rapid and there is now more ice than there was at this date in 2007 and 2012 (when polar bears in those regions considered most at risk did not die off in droves).
Pessimistic polar bear specialists are wrong – polar bears are much more resilient to low sea ice levels in summer than they assume: their own data from low summer ice years proves it. If you’ll recall from my previous post, polar bears seem to have barely survived the extensive sea ice coverage during the Last Glacial Maximum – in other words, too much ice (even over the short term) is their biggest threat. Polar bear numbers, as confirmed by the latest estimates in the 2015 IUCN Red List assessment, are higher now than they have been since the 1960s, despite almost 10 years of summer sea ice minimums below 5.0 mk2.
Churchill Polar Bear Alert reports and Arctic sea ice comparisons at this date, in detail below.
Posted in Conservation Status, Polar bear attacks, Sea ice habitat
Tagged Arctic, attacks, biggest threat, Churchill, facts, ice growth, last glacial maximum, minimum, polar bear, polar bear alert, population size, problem bears, Refuge, resilience, sea ice, September, summer, thick spring ice
Five years worth of sea ice maps for the same date is hard to come by in this country, since the Canadian Ice Service does not archive their daily sea ice maps. However, due to some forethought, I have at hand ice maps going back to 2012 for the longest day of the year for Canada and archives for other regions provide similar perspective at the solstice.
Few photos of polar bears in June likely exist – too early for most bears to come ashore and the ice too unstable for humans to be offshore [photo above is dated March].
Compare the five maps for Canada and eastern Alaska below. Notice the differences for Hudson Bay: it may seem ironic, but 2012 (which had the lowest September minimum since 1979 due to an August storm) had the most typical Hudson Bay breakup/melt pattern compared to previous years. [Keep in mind this recent post about how much ice can remain even when almost none is visible on the ice maps]
In many regions, polar bear hunting efforts are seldom successful after early June because young-of-the-year seal pups have taken to the water to feed, which means the only prey still on the ice are predator-savvy adults and subadults that have an easy time escaping in the rapidly breaking up ice fields. Bears that come ashore in June likely are not missing much – a little less ice than usual at this time of year is not going to make much difference.
Overall, despite doom and gloom predictions we heard in March 2016 (“wintertime extent hits another record low”), sea ice extent (courtesy NSIDC) at 20 June 2016 was the same at this date as it was in 2010 and 2012 at this time of year – which essentially marks the end of the primary feeding period for polar bears (except for those that live in the Canadian Arctic Archipelago, where seals give birth a bit later in the spring).
And did polar bears die in droves due to conditions in 2010 or 2012, in any subpopulation around the Arctic affected by low sea ice levels? No, they did not. In fact, the subpopulation that had the most recent survey done (Svalbard portion of the Barents Sea – 2015) was not only found to be thriving but numbers had increased markedly (42%) over 2004 levels. Now that’s resilience!
Posted in Life History, Sea ice habitat
Tagged Barents Sea, breakup, Canada, facts, Hudson Bay, polar bear, record low, resilience, sea ice, seals, solstice, Svalbard
With a few big guns on one side and some fringe folk on the other, a dichotomy of opinion has developed amongst polar bear researchers regarding whether or not consumption of land-based foods is making a difference to polar bear survival (or is likely to in the future).
It’s been going on for a while now. Last year, two US Geological Survey members of the IUCN Polar Bear Specialist Group (PBSG) apparently got fed up with the scatter-shot of papers promoting terrestrial foods as a possible salvation for polar bears (e.g. Iles et al. 2013; Iverson et al. 2014; Rockwell and Gormezano 2013a, 2013b). In April, they published a canon volley of a paper meant to blow all that ‘polar-bears-might-survive’ talk out of the water once and for all (Rode et al. 2015).
Note that although the PBSG didn’t bother to update their website with the IUCN Red List assessment when it came out last November, they had a link up to the USGS terrestrial feeding paper within 16 days (with an editorial summary in the “NEWS” section as well as a listing of the paper in the “RECOMMENDED READING” section). As I suggest below, this difference in treatment may not be a coincidence.
However, another group of non-PBSG researchers haven’t given up just yet, as shown by the title chosen for the most recent news report (Alaska Dispatch News, 16 June 2016) on the just-finished International Bear Conference:
Want to know how a changing climate is affecting polar bears? Look at what they’re eating.
Apparently, Jeff Welker, a University of Alaska Anchorage researcher who is co-author on two recent papers on the subject of polar bear consumption of terrestrial foods (Tartu et al. 2016 and Rogers et al. 2015), gave a presentation at the conference that raised this topic yet again. His talk came on the heels of an earlier presentation by Todd Atwood, who suggested Southern Beaufort polar bears might benefit from staying onshore to eat left-over whale scraps instead of staying on the sea ice during the summer (even though he had no data to support that opinion – as I discussed in this post).
Here’s the question: is this dispute really about what polar bears eat or don’t eat when they’re on land – or is it symptomatic of the underlying politics of polar bears? [CBC documentary video by that name here]
Posted in Advocacy, Conservation Status, Life History
Tagged adaptation, Amstrup, Atwood, criticism, diet, extinction, grizzly, IUCN, PBSG, polar bear, politics, Red list, resilience, Rode, sub-standard science, terrestrial foods, threatened, Welker
A new paper that combines paleoclimatology data for the last 56 million years with molecular genetic evidence concludes there were no biological extinctions [of Arctic marine animals] over the last 1.5M years despite profound Arctic sea ice changes that included ice-free summers: polar bears, seals, walrus and other species successfully adapted to habitat changes that exceeded those predicted by USGS and US Fish and Wildlife polar bear biologists over the next 100 years.
Cronin, T. M. and Cronin, M.A. 2015. Biological response to climate change in the Arctic Ocean: the view from the past. Arktos 1:1-18 [Open access] http://link.springer.com/article/10.1007/s41063-015-0019-3
Thomas Cronin is a USGS paleoclimatologist at the Eastern Geology and Paleoclimate Science Center, and Matthew Cronin is a molecular geneticist at the University of Alaska Fairbanks (see previous posts here and here about Matt’s work on the genetics of polar bear evolution).
From the Abstract:
Arctic climatic extremes include 25°C hyperthermal periods during the Paleocene-Eocene (56–46 million years ago, Ma), Quaternary glacial periods when thick ice shelves and sea ice cover rendered the Arctic Ocean nearly uninhabitable, seasonally sea-ice-free interglacials and abrupt climate reversals.
The final discussion and two summary graphics from this paper (copied below) are especially useful:
Posted in Evolution, Sea ice habitat, Summary
Tagged adaptation, Arctic, arctic seals, biological responses, climate change, climate extremes, Cronin, evolution, facts, genetics, glacial, he, ice-free summer, information, interglacial, LGM, marine mammals, paleoclimate, polar bear, resilience, sea ice, USGS, walrus
Evolution is not just for the long-term – natural selection also goes on over short time periods. In the case of polar bears, this adaptation is almost certainly critical for its long-term survival.
Hudson Bay female with cub Wapusk National Park, Thorsten Milse, Government of Canada
Not all polar bears are identical — that is the reality that allows natural selection to operate.
I will argue that early breakup years in Western Hudson Bay weed out individual polar bears that do not have the physiological or behavioral characteristics necessary to be useful members of the population – and that this is a good thing for the entire population.
Posted in Evolution, Population, Sea ice habitat
Tagged adaptation, declining sea ice, early breakup, evolution, historical sea ice record, indivdual variation, late freeze-up, natural selection, NSIDC, polar bear, resilience, sea ice minimum, sea ice variability, Stirling, Stroeve, survival, western hudson bay