You may have seen the headlines in Canadian news outlets over the last 2 days.
“Polar bears swimming farther as sea ice recedes, study shows”
“Melting sea ice forces polar bears to swim longer, farther: study” [“Bear biologist Andrew Derocher says the forced swims are particularly hard on mothers with young cubs”]
“Polar bears swimming longer, farther because of melting sea ice, study finds”
Oddly, none of the above news reports said where the paper was published or mentioned the name of the lead author – only University of Alberta co-author Andrew Derocher was interviewed (see the only press release I could find here, issued by the San Diego Zoo where the lead author is now employed).[update: CBC ran another story a day later that corrected these omissions]
But what did the study actually say?
Significantly, no bears died while swimming during the two lowest sea ice extent summers since 1979 and no evidence was presented that swims were “particularly hard on mothers with young cubs.” The quotes from the paper below sum it up for Beaufort Sea (BS) bears (the inclusion of Hudson Bay (HB) bears in this study seems gratuitous and potentially misleading, since only a few swam anyway – only 15 out of 59):
“….91% (91/100) of the swims in the BS occurred before the annual September minimum sea ice extent had been reached. …In the BS, 81% (29/36) of swims started and ended in pack ice…”
So, despite what may be implied during media moments, Beaufort Sea polar bears were not frantically trying to reach the sea ice from land so that they could attempt to keep feeding over the summer – most of their swimming was done during breakup in July and August from one bit of pack ice to another and they showed no evidence of harm from doing so. Map from the study and more quotes below.
Posted in Life History, Sea ice habitat
Tagged Beaufort, Derocher, forced swims, Hudson Bay, mothers with young cubs, Pilfold, polar bear, receding sea ice, sea ice, summer, swim longer, swimming, swimming further
It’s easy to take polar bear research papers at face value but it’s not very scientific. The snappy sound bites provided for the benefit of the media – whether they’re embedded in press releases or in published abstracts – don’t cut it with trained scientists. Trained scientists read the whole report, critically examine the evidence it contains and assess that evidence within the context of previous knowledge. That’s what they are trained to do.
I challenge the superficial summary on the status of Alaskan polar bear populations provided by FactCheck.org journalist Vanessa Schipani. Schipani disputed a comment made by Alaska Senator Lisa Murkowski that, according to the latest research Alaskan polar bear population numbers are strong and healthy. I’m not especially interested in the political context of the statement, only Schipani’s bald claim that Murkowski’s declaration is false.
I’ve read all the relevant papers in full and I contend that the evidence supports Murkowski’s statement. Schipani is confusing the issue by regurgitating ‘facts’ that don’t tell the truth of the matter. By the sum of accounts, Alaskan polar bear populations are indeed healthy and strong – whether or not this status will continue is an entirely different question. Continue reading
Posted in Conservation Status, Population
Tagged Alaska, Beaufort, Chukchi, conservation, ESA, facts, IUCN, polar bear, population size, Red list, ringed seals, sea ice, status
Good news for Southern Beaufort polar bears! Sea ice converging on the north shore of Alaska earlier than any year since 2011 at least, according to NSIDCs regional ice plots (below).
But wait, their Masie ice maps show it’s actually the earliest since 2008 (although the ice movement onshore was also earlier than 2006 and 2007, see below). And it’s still a full week before the end of October, the first month of Arctic fall (October-December). Lot’s of seal hunting habitat.
This emphasizes the fact that the primary problem faced by Southern Beaufort sea polar bears is not scarce summer ice but by thick sea ice conditions in the spring. Bears photographed near Kaktovik this year were in excellent condition (see here and here, taken by Kelsey Eliasson, Polar Bear Alley). If folks have been seeing starving bears, they haven’t said anything that I’ve been able to find.
Ice maps below.
At the seasonal minimum 2015, the Arctic Basin was still almost full of sea ice, down only 0.3 mkm2 below the maximum it could ever be.
Remember that spending the summer in the Arctic Basin for most polar bears is just like sitting on the western shore of Hudson Bay – they are all waiting for the refreeze. In either location, they might find something to eat, they might not.
Below are NSIDC MASIE sea ice maps for 10 April 2015 (as big as it gets, basin filled) vs. 17 September 2015: Continue reading
Two out of seven polar bears with collars in the Southern Beaufort Sea either spent the month of August on ice that satellites couldn’t see – or they spent the entire month swimming around the Beaufort. Which seems most likely?
See previous discussions here and here regarding the problem satellites have in accurately detecting melting ice. The presence of these two bears is evidence that there is more polar bear habitat than satellites record as officially present. This was also an issue for Hudson Bay bears earlier this year.
Five out of the seven visible females were on the ice in August – but are the other six bears that were visible last month spending the summer in the Arctic Basin like the one I reported last week? Or have their collars actually failed or dropped off? USGS isn’t saying.
See the August track map below, from the USGS Tracking Polar Bears website1 and a sea ice map.
Sea ice in at least three Eastern Canadian polar bear subpopulations is well above normal for this time of year, which means many bears are likely not ashore yet. The same is true in the Beaufort and Barents Seas – ice is melting but there is still a fair amount of sea ice close to popular shores. Cause for cheering, not raising alarms.
Southern Hudson Bay, Foxe Basin, and Davis Strait, all have above average sea ice coverage, according to the Canadian Ice Service (see charts below).
Hudson Bay ice levels are particularly striking: the anomaly map below (“departure from normal”) is almost entirely blue (positive), showing how far it is above average. No wonder supply ships needed icebreaker help yesterday to get into Inukjuak on the eastern shore. Most of the ice is technically in the Southern Hudson Bay polar bear subpopulation region, which has a stable population.
Posted in Conservation Status, Sea ice habitat
Tagged Beaufort, Davis Strait, habitat, Hudson Bay, melt, polar bear, science, sea ice, Southern Hudson Bay, summer, Svalbard
The Obama administration is apparently attempting to overturn a previous ruling that rejected proposed Alaskan “critical habitat” for polar bears in 2013 – as if “critical habitat” would protect the bears from the repeated episodes of thick spring ice that develop in this region every 10 years or so.
According to a Reuters report today (5 May 2015):
“Seeking to reverse a ruling throwing out its designation of critical habitat for polar bears, the Obama administration has defended its decision to list large swathes of the Arctic as necessary for the conservation of the threatened species.
A coalition of oil industry groups and Alaska Natives, represented by Stoel Rives and Holland & Hart, successfully persuaded the U.S. District Court for Alaska to vacate the government’s polar bear habitat designation in 2013.” [my bold]
If they succeed, it would put most of the north coast of Alaska under special ESA rules, as the map below shows (click to enlarge).
As I commented previously, regarding the Obama administration’s recommendation to congress that they approve a proposed Arctic wildlife refuge area on Alaska’s North Slope, this move (if implemented) would not protect polar bears from the starvation deaths due to thick spring ice conditions that have occurred in this region for 2-3 years out of every 10 since 1960 at least.
The other issue is how much additional, biologically meaningful protection a critical habitat designation would provide for Southern Beaufort and Chukchi Sea polar bears – over and above that already provided by the Marine Mammal Protection Act.
Posted in Conservation Status, Sea ice habitat
Tagged Alaska, Beaufort, Chukchi, conservation, critical habitat, ESA, Marine Mammal Protection Act, mortality, polar bear, sea ice, thick spring ice, threatened, US Fish and Wildlife Service