Bumblebee populations are in decline across North America and Europe due to hotter and more frequent extremes in temperatures, and climate change is playing a big role, according to a recently released study.

The study by researchers from the University of Ottawa published in the journal Science examined changes in the populations of 66 bumble species across the two continents, and compared them with climate changes.

The research found that in the course of one human generation, the likelihood of a bumblebee population surviving in a given place in North America and Europe declined by an average of more than 30 percent.

“We’ve known for a while that climate change is related to the growing extinction risk that animals are facing around the world,” lead author of the study Peter Soroye said in a statement.

“Bumblebees are the best pollinators we have in wild landscapes and the most effective pollinators for crops like tomato, squash, and berries,” Soroye said. “Our results show that we face a future with many less bumblebees and much less diversity, both in the outdoors and on our plates.”

Researchers used data collected over a 115-year period showing where bumblebees have been found over the decades. They mapped the places the bees lived and how their distribution changed over time. They found the bees were disappearing in areas that had gotten hotter, and some are colonizing in new areas that were previously too cold.

But researchers say the bumblebees are not colonizing new regions at the same rate they’re disappearing from old ones.

“It’s these extreme events throughout the year that’s pushing bees beyond what they’ve ever had to handle before,” Soroye said. “And that seems to be driving a lot of the disappearances in bees.”

Researchers warned that if declines of species continue at this pace, many of these species could vanish forever within a few decades.