Four bumblebee species once common across North America have suffered precipitousóand so far mysteriousódeclines, a new study shows.
Within the past 20 years abundances of the bee species Bombus occidentalis, B. affinis, B. pensylvanicus, and B. terricola have plummeted by up to 96 percent.
The finding is based on a new analysis of more than 73,000 museum collections of bumblebees, which showed where bees had been found over the last century, as well as collections of wild bees across the United States. The study looked at 8 of the 50 known bumblebee species in North America.
“We found that yes, indeed, [these four species] are seriously declining, but there are some other species doing very well,” said study co-author Sydney Cameron of the University of Illinois’ department of entomology.
The discovery makes it harder to pinpoint pesticides or climate change as a cause for the bug die-off, because those factors wouldn’t explain why other bumblebee species in the same areas have survived.