Bumblebee populations failing to track warming trends caused by climate change, study says

A study published in Science found that unlike most species, "many North American and European bumblebees are failing to 'track' warming by colonizing new habitats north of their historic range. Simultaneously, they are disappearing from the southern portions of their range," Cally Carswell reports for Science. (The two-spotted bumblebee, found in eastern North America, is one of about 250 bumblebee species worldwide)

The study, which consisted of 423,000 observations of 67 bumblebee species in North America and Europe since 1901, "found that some bumblebees have retreated as many as 300 kilometers from the southern edge of their historic ranges since 1974," Carswell writes. "Southern species are also retreating to higher elevations, shifting upward by an average of about 300 meters over the same time period. Meanwhile, few species have expanded their northern territories. And it turned out that climate change was the only factor that had a meaningful impact on the large-scale range shifts."

While pesticides have been partially blamed for the demise of bumblebee populations, "one clue to the importance of climate: bumblebee ranges began shrinking 'even before the neonicotinoid pesticides came into play in the 1980s,' says ecologist and coauthor Alana Pindar, a postdoctoral fellow at the University of Guelph in Canada," Carswell writes. "She says the retreat from southern territories is 'a huge loss for bumblebee distributions' and happened surprisingly quickly. The researchers believe the retreat—and the move to higher elevations—may reflect the fact that bumblebees evolved in cooler climates than many other insects that haven't yet lost ground and so are especially sensitive to warming temperatures." (Read more)