Early last November, sea ice around Svalbard was the lowest it had been since 1967 and pregnant females were simply unable to den on the eastern islands of the archipelago and instead had to make their dens and give birth in the pack ice or the Franz Josef Land archipelago further east, as they have done before. However, the ice is back this fall with a vengeance: even Hopen Island in the south of region was surrounded by ice well before the end of the month but whether it will attract a few pregnant females remains to be seen.
Results of polar bear health monitoring in the spring of 2021 indicated the bears are doing just fine after last year’s low ice levels. Despite this evidence, a single bear photographed killing a reindeer in August 2020 was falsely blamed on climate change. The narrative never seems to change.
Maternity dens and sea ice
Polar bear cubs are born in late December to early January and most females attempt to have a den prepared well before this event. Pregnant females that prefer to den in eastern Svalbard but are unable to reach these areas due to lack of sea ice in the fall are known to make their dens in the pack ice or within the Franz Josef Land archipelago further east (Aars 2015; Aars et al. 2017; Andersen et al. 2012). This flexibility in the face of variable sea ice conditions is an obvious evolutionary survival mechanism that has provided the species with the necessary resilience to endure hundreds of thousands of years of natural sea ice variability (both much more ice and much less ice than was present in 1980).
Vocal polar bear specialist Andrew Derocher spent several years studying Svalbard bears in the late 1990s when summer sea ice conditions were beginning to change (Derocher 2005; Derocher et al. 2002, 2011). He fully embraced his Ph.D. supervisor’s unfounded suggestion that only human-caused global warming could account for the changes he had witnessed (Crockford 2019). Despite the fact that recent studies have shown that Svalbard bears are doing better now than they were in the 1980s (Lippold et al. 2019), he continues to dispense his ritual fearmongering whenever Svalbard ice varies downward (see below).
The graph Derocher pulled from his 2011 paper on Hopen Island maternity denning vs. ice levels in the above tweet suggests that at least some females should use the island if sea ice reaches it before the end of November, as it did this year (see below). Hopen is the long skinny island at the south-eastern edge of the ice (the island is actually easier to locate in the 2020 chart below):
However, monitoring data reveals that no bears have used the island since 2010 (below), despite good fall ice coverage by the end of November in 2019 and 2014, so it may be that pregant females have abandoned it for now.
Sea ice in 2021 vs. previous years at end November
This year at 29 November:
Compare to last year (2020) near this date:
And the year before, in 2019:
And below, late November Svalbard ice coverage from 2018 to 2012.
Bottom line: Despite record-breaking fall ice levels in 2020, on top of this region having the highest relative decline in summer sea ice of all polar bear subpopulations (Regehr et al. 2016), there is no signature of impending disaster in the spring 2021 polar bear monitering data or research done prior to that (e.g. Lippold et al. 2019): no starving males, poor cub surivval, or large numbers of females without cubs. Last summer should have been the ‘tipping point’ for this population, according to the models. But adequate winter and spring ice developed as it has always done and the bears are still thriving, as they were in 2015 (Aars 2018; Aars et al. 2017).
Aars, J. 2015. Research on polar bears at Norwegian Polar Institute. Online seminar (‘webinar”), January 14. pdf here.
Aars, J., Marques,T.A, Lone, K., Anderson, M., Wiig, Ø., Fløystad, I.M.B., Hagen, S.B. and Buckland, S.T. 2017. The number and distribution of polar bears in the western Barents Sea. Polar Research 36:1. 1374125. doi:10.1080/17518369.2017.1374125
Andersen, M., Derocher, A.E., Wiig, Ø. and Aars, J. 2012. Polar bear (Ursus maritimus) maternity den distribution in Svalbard, Norway. Polar Biology 35:499-508.
Derocher 2005. Population ecology of polar bears at Svalbard, Norway. Population Ecology 47:267-275.
Derocher, A.E. and Wiig, Ø. 2002. Postnatal growth in body length and mass of polar bears (Ursus maritimus) at Svalbard. Journal of Zoology London 256:343-349.
Derocher, A.E., Andersen, M., Wiig, Ø., Aars, J. and Biuw, M. 2011. Sea ice and polar bear den ecology at Hopen Island, Svalbard. Marine Ecology Progress Series 441:273-279.
Lippold, A., Bourgeon, S., Aars, J., Andersen, M., Polder, A., Lyche, J.L., Bytingsvik, J., Jenssen, B.M., Derocher, A.E., Welker, J.M. and Routti, H. 2019. Temporal trends of persistent organic pollutants in Barents Sea polar bears (Ursus maritimus) in relation to changes in feeding habits and body condition. Environmental Science and Technology 53(2):984-995.
Regehr, E.V., Laidre, K.L, Akçakaya, H.R., Amstrup, S.C., Atwood, T.C., Lunn, N.J., Obbard, M., Stern, H., Thiemann, G.W., & Wiig, Ø. 2016. Conservation status of polar bears (Ursus maritimus) in relation to projected sea-ice declines. Biology Letters 12: 20160556. http://rsbl.royalsocietypublishing.org/content/12/12/2016055
December 1, 2021