Climate change contributed to drastic declines in the population and diversity of bumblebees across North America and Europe, according to a long-term study of more than 60 bee species published in the journal Science.

Researchers discovered bumblebees are disappearing at rates "consistent with a mass extinction."

The scientists said North America's bumblebee populations fell by 46 per cent during the two time periods the study used - from 1901 to 1974 and from 2000 to 2014.

Bee populations were hardest hit in warming southern regions such as Mexico, because of more frequent extreme warm years, which exceeded the species' historical temperature ranges, according to the study.

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"If declines continue at this pace, many of these species could vanish forever within a few decades," study lead author Peter Soroye, a Ph.D. student at the University of Ottawa, said in a statement.

"We've known for a while that climate change is related to the growing extinction risk that animals are facing around the world. In this paper, we offer an answer to the critical questions of how and why that is," Soroye said.

"We find that (bee) species extinctions across two continents are caused by hotter and more frequent extremes in temperatures."

The study found that in the course of a single human generation, the likelihood of a bumblebee population surviving in a given place has declined by an average of more than 30 per cent.

DOUG FIELD/STUFF Many bumblebee species could vanish within a few decades.

Bumblebees are the best pollinators in wild landscapes and the most effective pollinators for important crops such as 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."

In an accompanying perspective article in Science, Jonathan Bridle and Alexandra van Rensburg of the University of Bristol wrote, "The new study adds to a growing body of evidence for alarming, widespread losses of biodiversity and for rates of global change that now exceed the critical limits of ecosystem resilience."

Soroye concluded, "We have now entered the world's sixth mass extinction event, the biggest and most rapid global biodiversity crisis since a meteor ended the age of the dinosaurs."

- USA Today