On bumblebees and northern ranges

There has been much buzzing in the press in the last few days, about the apparent lack of evidence that temperate bumblebees are expanding their northern range in the face of apparent global warming in the Arctic…

Kerr et al. looked at data on bumblebees across North America and Europe over the past 110 years. Bumblebees have not shifted northward and are experiencing shrinking distributions in the southern ends of their range.”

It seems quite obvious — even to a layman — why temperate bumblebees might be only slowly edging north out of sub-arctic areas.

Any northward move would likely encounter Bombus Polaris, the common Arctic bumblebee. But to say that this large bee is common would be to denigrate it. It is a ‘super-bee’ — one that happily survives the deep Arctic winter, can rapidly warm itself bio-mechanically to 38 degrees (the same as a human), can fly in intense below-zero springtime cold and wind, and is generally incredibly well-adapted to breeding early and well in the Arctic. B. Polaris‘s IUCN Red List status is “Least Concern”, and it is well-distributed in America and Russia (though rather hemmed in by the ocean in Norway, and possibly vulnerable there in the distant future).

So it strikes me that no temperate bee could possibly complete with such a ‘super-bee’ for the vital early nectar, in such adverse conditions. Nor could it, perhaps, compete with the vicious swarms of Arctic flies that come later. Or with the various parasites that Bombus Polaris appears to be well adapted to. Sadly the academic paper in question doesn’t even consider this possibility, and even seems to imply that the Arctic north is “unoccupied” by bumblebees…

“Colonization of previously unoccupied areas and maintenance of new populations strongly affect whether species track shifting climatic conditions, capacities that appear insufficient among bumblebees.” (my emphasis)

Incidentally, a key far-northern temperate bumblebee is actually doing fairly well in terms of its “capacities” for survival in the sub-Arctic, at least according to a major 2015 Alaska study

“the western bumble bee, Bombus occidentalis. … was collected from all three sites and represented roughly 10% of the total specimens, suggesting that B. occidentalis is a relatively abundant species in the areas studied.” (my emphasis)

Worst case scenario, from all this: Someone decides to import temperate sub-Arctic bees and acclimatise them to the allegedly “unoccupied areas” on the borders of the Arctic. These bees introduce some nasty parasite or disease to the previously isolated Bombus Polaris, and then themselves fail to fill the niche. The increasingly rare B. Polaris is then found to have played some key but unknown role in keeping Arctic tundras stable via early pollination, and as a result of the bumblebee disappearance the Arctic gas hydrates are seeping out and causing massive global warming… ooops!

Such blundering errors by scientists are not unknown

“… scientists are now agreed that the golden toad’s demise, and that of up to 30 other amphibians in central America, was caused by a chytrid fungus, originating in Africa, to which frogs on other continents are especially vulnerable. How did the fungus reach the Americas? Through the use by scientists of the African clawed toad as a popular laboratory animal. The clawed toad carries the fungus but does not die from it, and has escaped into the wild in many places.”