Have polar bears suffered a contraction of their historical range due to recent declines in summer sea ice? Buried in a recent journal article lies such a claim, one I can’t recall having seen before. That makes it worth close examination.
A drawing of polar bears on St. Matthew Island that accompanied the May 1, 1875 Harper’s Weekly Journal of Civilization article written by Henry Elliot. See here.
The assertion appears in the introduction of a recently published paper that got a lot of attention online (“Implications of the Circumpolar Genetic Structure of Polar Bears for Their Conservation in a Rapidly Warming Arctic” by Peacock and colleagues (2015), discussed previously here, news coverage here and here).
Here is how the authors put it:
“There is already evidence of change in the contemporary distribution of polar bears. For example, polar bears, once common in Newfoundland , are now seen there only infrequently and in small numbers. Similarly, polar bears once regularly summered on St. Lawrence and St. Matthew islands in the Bering Sea [30–32]. Now they are irregularly observed in the Bering Sea and do not spend summers on St. Matthew Island. Although these changes in polar bear distribution may also have been related to overharvest, the recent reductions in the extent of sea-ice due would prevent current and regular use of these areas.” [my emphasis]
There are three main reasons the claim doesn’t hold up to scrutiny:
Posted in History, Sea ice habitat
Tagged climate change, global warming, Gulf of St. Lawrence, Labrador, Little Ice Age, Medieval Warm Period, Newfoundland, range, range contraction, sea ice, St. Lawrence Island, St. Matthew Island, Vibe
Did you know there used to be resident polar bears on two small islands in the Bering Sea? Given how much we don’t know about the polar bears of the Bering Sea, the bears that used to den and spend their summers on the St. Matthew Islands are a bright spot. These islands lay at the southern-most limit of the modern “Chukchi Sea” subpopulation (see Fig. 1) and were uninhabited by people when they were discovered in the 1760s – but they were a haven for polar bears.
We have details of the polar bears that gave birth and summered there because a US government biologist (Henry Wood Elliott) and a US navy Lieutenant (Washburn Maynard) surveyed the islands in 1874. Elliott wrote both an official report and a popular magazine article (for Harper’s Weekly Journal of Civilization) in 1875 describing the polar bears they saw; Maynard wrote a separate report in 1876. By 1899, there were none left, victims of the relentless slaughter of polar bears everywhere in the Arctic in that era (see previous discussion here).
Figure 1. St. Matthew Island is in the Bering Sea off the west coast of Alaska at about 60°N latitude. Compare this to the southern end of James Bay, Canada (which has a stable population of polar bears) at about 53 0N and Churchill, Manitoba (the so-called “polar bear capital of the world) at 58 046’N. Maps from Wikipedia.
Figure 2. A drawing of polar bears on St. Matthew Island that accompanied the May 1, 1875 Harper’s Weekly Journal of Civilization article written by Henry Elliot. See here.
[UPDATE: Jan. 27, 2013: a follow-up to this post is here.]
Posted in Life History, Sea ice habitat
Tagged Bering Sea, Chukchi, commercial harvest, Elliott, Hudson Bay, Klein, onshore, Rozell, sea ice extent, St. Matthew Island, triplets