Looking at historic and scientific data over the past 110 years, a new study found that rising temperatures have squeezed bumblebees into ever declining habitable areas. The scientists estimate, that bumblebees across Europe and Northern America have lost about 300 km in the south while gaining nothing in the north.
Other insects, such as butterflies, have migrated north to cooler climates, but bumblebees have not done so. Looking for reasons for this plight, the scientists suggest an evolutionary explanation. Many insect species originated in tropical climates. As temperatures warm, their evolutionary history seems to help them to adapt. Bumblebees however, have evolutionary origins in the cool Palearctic region. As a result, bumblebees may be unable to cross inhospitable tracts of land hemming them in. Stuart Roberts, from the University of Reading, co-author of the study says: “Bumblebees might be able to live in climatically suitable habitats further north, but many of them just can’t get there. Large swathes of land in some parts have become so degraded and inhospitable that bees can’t travel across them to find the more suitable homes that are opening up further north.”
Instead of moving north, some bumblebees are moving up: if they live in mountainous habitats, they tend to shift to areas at higher elevation in response to climate change. Even though this move saves them for the moment, it will be fatal in the long run, says Leif Richardson, scientist at the University of Vermont and co-leader of the study: “Moving upslope doesn’t necessarily mean they’ve lost area there yet, but eventually, they may simply run out of hill.”
To respond to this problem, the research team suggests moving bee populations into new areas where they might persist. This “assisted migration” idea has been considered in conservation biology circles for more than a decade. Even though strategy is controversial, it is gaining support as the warming continues.
The study “Climate change impacts on bumblebees converge across continents” was published in the Science Journal and also widely covered in media by the British Mirror and the University of Vermont.