Climate change is crushing bumblebee populations, scientists have found

Bumblebees are in some respects remarkably uniform in form and behavior. Their colonies can be considered as individual so-called superorganisms, because the reproductive unit subject to Darwinian selection is the entire colony, not individuals. An important feature of the superorganism concept is the ability of the entire colony to maintain a temperature within a range in which the rate of metabolism is minimal and activity can be maintained.

In hot weather, workers gather to flap their wings and ventilate the hive, cooling it down. However, a new study signed by a trio of authors from universities in Canada and Belgium shows that even with this ability bumblebees will probably not be spared from climate change.

“Most bumblebee hatchlings would not survive at temperatures above 36°C,” according to a paper published in the journal Frontiers in Bee Science. According to entomologists, the optimal temperature range for nest incubation is between 28 and 32 degrees.

The lead author of the study, Petr Kevan from the University of Guelph in Canada, then told The Guardian that the very nature of the nest as a superorganism can be fatal for bumblebees. “While some individual bees may be able to cope with the heat, if the nest becomes too hot to raise healthy larvae, the entire colony will perish,” he said.

Not only bumblebees are threatened by global warming

Therefore, global warming is the main reason why their numbers are decreasing significantly. Environment America, a federation of state environmental organizations in the United States, wrote in January 2022 that the number of American bumblebees alone, one of about 250 bumblebee species, has declined by an alarming 90% over the past twenty years.

A 2020 study in the prestigious science journal Science reports that the likelihood of any bumblebee species has dropped by 46% in North America and 17% in Europe compared to the 20th century.

The bumblebee is one of the most important pollinators, especially for fully growing flowers and crops such as tomatoes, apples, beans, blueberries or black currants.

Richard Comont, science manager at Britain’s Bumblebee Conservation Trust, says the outlook for other pollinators in a warmer climate is less clear. Some bee species will adapt to warmer temperatures, and some species that now live further south may move north to find a new home as temperatures rise.

However, unlike them, bumblebees have nowhere to travel for the cold. “We’ve known for a long time that bumblebees are cold climate specialists. Most insects are more abundant in the tropics, but bumblebees are special in that they are most abundant in cold places,” added Dave Goulson, professor of biology at the University of Sussex. Some of the most abundant colonies live in the Alps and Great Britain. Their body – large and hairy – is actually an adaptation to life in colder places.