Introducing their work, Stapleton et al. (2016) write that polar bears (Ursus maritimus) are “considered among the most highly sensitive marine mammals to the projected consequences of climate change,” citing Laidre et al. (2008). Indeed, increased sea ice losses projected for mid-century have led to concerns that “polar bears may be extirpated from or substantially reduced across most of the circumpolar Arctic.” As a result, the Arctic polar bear has become the proverbial canary in the coal mine for those seeking proof of climate change impacts in the far northern latitudes of our planet. Efforts have long been under way to study trends in these northern mammals and relate those trends to changes in climate.
The study of Stapleton et al. is no different in this regard. Their objective was to provide an updated analysis of the polar bear population within the Foxe Basin of Canada, a region that spans 1.1 million square kilometers across the Nunavut territory and northern Quebec. Last inventoried in the early 1990s, the Foxe Basin has been identified as a region of concern as climate conditions over the period 1979-2008 have led to a deterioration of the sea ice habitat (Sahanatien and Derocher, 2012) that has long been thought to engender a stable polar bear population. Against this backdrop of potential decline, Stapleton et al. set out to conduct an updated population survey of polar bears in this region to discern whether or not declining sea ice conditions had indeed affected their numbers as model-based projections claimed it would. And to this end, the three researchers conducted a series of aerial surveys in late summer of 2009 and 2010.
So what did their survey reveal?
Following rigorous statistical analysis of their data Stapleton et al. report a current average estimate of 2,585 polar bears in the Foxe Basin, which is similar to the last estimate of 2,200 obtained in 1994. This new number, along with evidence of “robust cub production,” in the words of the authors, “suggests a stable and healthy population despite deteriorating sea ice conditions.” “In other words,” as Stapleton et al. emphatically conclude, “the deterioration of sea ice habitat has not resulted in a decline in [polar bear] abundance.” Thus, it would appear that this canary of the north has so far been oblivious to alarmist predictions of its demise.
Laidre, K.L., Stirling, I.,Lowry, L.F., Wiig, Ø., Heide-Jørgensen M.P. and Ferguson, S.H. 2008. Quantifying the sensitivity of Arctic marine mammals to climate-induced habitat change. Ecological Applications 18: S97–S125.
Sahanatien, V. and Derocher, A.E. 2012. Monitoring sea ice habitat fragmentation for polar bear conservation. Animal Conservation 15: 397–406.
Stapleton, S., Peacock, E. and Garshelis, D. 2016. Aerial surveys suggest long-term stability in the seasonally ice-free Foxe Basin (Nunavut) polar bear population. Marine Mammal Science 32: 181-201.