Posted onDecember 11, 2022|Comments Off on Polar bear habitat update: Winter conditions well on their way across the Arctic except in Svalbard
December is late fall in the Arctic: winter conditions are gearing up but are not in full swing everywhere. Sea ice is developing quickly over Hudson Bay and moving slowly towards the Bering Sea but the Svalbard archipelago is still devoid of pack ice.
Such conditions north of Norway have existed most years since 2005: it’s certainly not a new development for Svalbard to be free of surrounding pack ice in December (although there was lots of ice in 2019 and 2021 by late November). This means traditional denning areas on the eastern islands again cannot be used by pregnant polar bear females, because they must be ensconced in their dens by at least late November or so.
Some seem to think this is a calamity: that such ‘loss of habitat’ is a huge concern for the survival of the subpopulation, if not the entire species. However, the same conditions existed in 2011 and did not result in a dramatic decline in the population as measured in 2015 (Aars et al. 2017) because the bears knew how to respond. They have apparently moved north to make maternity dens on the sea ice or east to the Franz Josef Land archipelago in Russia (Aars 2015). These areas are still within the Barents Sea subpopulation boundaries and researchers have known for two decades that bears have moved around within it (Andersen et al. 2012; Derocher 2005; Maurizen et al. 2002).
Posted onMarch 1, 2021|Comments Off on More polar bear catastrophe hype: bears use four times more energy than expected
Last week (24 February 2021), The Guardian was promoting a study that claims polar bears now use four times more energy than expected to survive because of ‘major ice loss’ in the Arctic, as a way of suggesting that the animals are already on their way to extinction.
But like many papers of this type, this study by Anthony Pagano and Terri Williams (Pagano and Williams 2021) is yet another model describing what biologists think may be happening based on experimental data collected from individual bears, not a conclusion based on evidence collected from subpopulations with the worst amounts of ice loss.
Posted onAugust 9, 2015|Comments Off on Summer polar bear habitat then & now – little impact from 2007 record-breaking sea ice low
Sea ice looks low for this time of year but how does it compare to 2007, when summer ice habitat for polar bears hit a record-breaking low? What can the impact of 2007 ice levels on polar bears tell us about what to expect this year?
By this date in 2007 (8 August, Day 220, NSIDC Masie map below), there was almost 1 million km2 less ice than there is this year (map above). However, look which polar bear subpopulations not only survived, but thrived, through the 2007 low ice summer: Chukchi Sea, Southern Beaufort, Barents Sea, Davis Strait, Foxe Basin, Western Hudson Bay, and Southern Hudson Bay. That’s all of the subpopulations for which we have recent data.
There is more than a month left in the melt season, of course. However, while 2012 finished with a lower minimum ice extent due to a massive mid-August storm that broke up a lot of ice (Simmonds and Rudeva 2012), by the end of the first week of August (i.e, the 8th), there was more ice in 2012 than in 2007 and a bit less than this year (2012, 6.3 mkm2; 2007, 5.6 mkm2; 2015, 6.5 mkm2).
This means if less summer ice for a longer period of time impacts polar bear health and survival, conditions in 2007 should have had a noticeable impact on polar bears around the world. They didn’t. That suggests even if this September sea ice minimum is as low as 2007, it won’t have any negative impact on polar bear health or survival. The most profoundly negative documented impacts have come from thick sea ice in spring or suboptimal spring snow levels (Crockford 2015) and the evidence shows that variation in the extent of summer ice is simply irrelevant to polar bears.