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Rising global temperatures may be making bumblebee nests too hot for them to survive.

The global bumblebee population has declined since the 1950s, sparking speculation on the causes – researchers have suggested everything from pesticides to habitat loss. Because bumblebees are vulnerable to temperature swings, some have proposed another culprit: climate change.

Researchers from the University of Guelph in Canada reviewed studies dating back to the 1800s and found that, regardless of species or region, bumblebees prefer a nest temperature between around 28 and 32°C (82-90°F). When nest temperatures surpassed 36°C (97°F), the bees couldn’t continue reproducing, adding new evidence to the idea that increased heat could be partly to blame. Because the larvae – young bees that resemble worms – are more sensitive to heat than adults, one brutal heatwave could kill a nest’s next generation.

“It’s remarkable that all the way from the high Arctic to the tropics, bumblebees seem to have the same sort of nest temperature requirements,” says at the University of Guelph. “If it gets too hot… it’s quite likely that they will die.”

Bumblebees protect growing larvae by fanning their nest with their beating wings. But this defence may not be enough to compensate for worsening climate change. High-tech innovations like a robotic  could offer some insurance for commercial honeybee operations, says Kevan, but aren’t a practical solution for roaming wild bees.

It is still crucial to consider other bumblebee threats, like pesticides and habitat loss. Efforts like planting native wildflower gardens can create much-needed habitat, but without also addressing warming, says Kevan, bumblebees may face a harrowing future.