Buzzing off
Each year bumblebees have a little less natural habitat, new research shows. By Nicholas St Fleur
Climate change has narrowed the range where bumblebees are found in North America and Europe in recent decades, according to a new study. The paper, in the journal Science, suggests warming temperatures have caused bumblebee populations to retreat from the southern limits of their travels by as much as 190 miles since the 1970s.
Logic suggests the northern reaches of their home turf would shift to higher latitudes by a corresponding distance. But that has not happened, leading researchers to think the more northern habitats may be less hospitable to them.
“Bumblebee species across Europe and North America are declining at continental scales,” says Jeremy Kerr, a conservation biologist at the University of Ottawa in Canada and lead author of the report. “Our data suggests climate change plays a leading, or perhaps the leading, role in this trend.”
Not all entomologists agree with the findings, saying that the paper offers evidence of a correlation between climate change and waning bumblebee population ranges, but does not make the case that warming temperatures are the main cause. Instead, they say a multitude of factors contribute to the bumblebees’ shrinking borders.
For the study, the researchers constructed a database containing more than 420,000 observations of 67 European and North American bumblebee species, including when and where they were found. The museum records stretch back more than 110 years.
The researchers analysed the observations along with climate information from every year from 1900 to 2010 and drew conclusions about how the northern and southern limits of different bumblebee species shifted over the past century.
They compared population changes from 1974 to 2010, when temperatures began to warm, with changes from 1901 to 1974, when human-caused climate change was less of a factor. They found the southernmost range of bumblebees retreated north at a rate of about three miles per year.
“One of the most striking results was that trends were often indistinguishable between Europe and North America,” says Paul Galpern, a landscape ecologist from the University of Calgary and a co-author of the paper. “Bumblebee species are responding quite similarly across continents since climate change began to really accelerate from 1975.”
The findings did not entirely surprise Dave Goulson, a bee biologist at the University of Sussex who was not part of the study. He