Bumblebees Can’t Take the Heat as the Climate Warms

A new study finds that the pollinators are vanishing from hundreds of miles of their range as temperatures rise, but they're not moving north.
(Photo: Damien Meyer/AFP/Getty Images)
Jul 9, 2015· 1 MIN READ
Katharine Gammon has written for Nature, Wired, Discover, and Popular Science. A new mom, she lives in Santa Monica.

A warming climate is pushing bumblebees to the brink in North America and Europe, where the pollinators have lost up to 186 miles of their southern range, according to a study published Thursday.

Worse, unlike other climate-stressed species, bumblebees are not migrating north as the weather warms, scientists found.

“Though different species of bumblebees live in different places and have slightly different tolerances to temperature variations—some bees like a little more warmth,” said Jeremy Kerr, a biologist at the University of Ottawa and the lead author of the paper, which was published in the journal Science. “But in common to all of them is a relative incapacity to deal with hot weather.”

The scientists had a reliable trail of data to tap when it came to bees: specimens tucked away in natural history museums around the world, along with information about where the insects were found. The international team of researchers created a database of 67 species of bumblebees in Europe and North America, totaling 423,000 observations.

When they crunched the data, they were left stunned, Kerr said. Bumblebees’ southern range was rolling up like a carpet, and they weren’t moving into new potential habitat to the north.

“There is lots of evidence to see that species are adapting—a little or a lot—to climate change,” said Kerr. “Bumblebees are not, and we thought they would.”

As their range constricts, their population is shrinking, falling significantly in areas where bees were thriving just a few decades ago.

RELATED: Bees Are Dying Year-Round Now

The researchers also evaluated the impact of land use and pesticides in relation to the range loss and found no significant correlation. But Kerr noted that pesticides such as neonicotinoids are known to cause bee deaths.

“It could be that neonicotinoids and climate change are acting as a one-two punch for bees,” he said. “We need to understand how multiple stressors are interacting.”

If bees could be transported 60 miles north to new habitats, they might be able to establish a foothold in the environment. Some scientists propose relocating climate-threatened species, though the idea continues to be debated.

So, Why Should You Care? Populations of honeybees, which pollinate a third of the world’s food supply, have been plummeting over the past decade because of what scientists believe is a complex interplay of pesticides, parasites, and poor nutrition. Kerr said maintaining a diverse group of pollinators, including bumblebees, reduces the risk of relying on any one insect.

“Biodiversity is like insurance,” he said. “If you only have one species in the environment and some new factor comes along and takes them out, then you’ve got nothing left in the arsenal. To be frank, this is not a group of organisms we can do without.”