North America's Losing Its Bumblebees

One bumblebee species that was once common throughout its range from Georgia State to Ontario, Canada has all but disappeared. A recent survey at places where Bombus affinis has been collected previously turned up empty handed in all but one location. Just a single bee was found on a woodland sunflower in southern Ontario's Pinery Provincial Park.

Bombus affinis used to frequent the farmlands, marshes and woods of eastern North America. It's been seen visiting many different kinds of plants, including ones that play important economic or ecological roles.

Although researchers at Toronto's York University captured 9,000 bumblebees from 2005 to 2007, they didn't find B. affinis among these at 42 locations. They searched sites in 14 states where the bees were collected before, including South Carolina, Tennessee, Virginia, Pennsylvania, Michigan and Maine.

A more detailed survey of wild bees around Guelph in southern Ontario finds that this isn't the only native bumblebee species to have disappeared there in the last 35 years. Two other Bombus species (B. pensylvanicus and B. ashtoni) that had been collected in the early 1970s were not among those recently netted. The region used to be particularly rich in bees, with 14 Bombus species identified in earlier surveys.

This research provides the first quantitative evidence from North America indicating the severity of recent losses among native pollinators. In Europe where bumblebees are more closely monitored, findings show that half the continent's species are declining. Three species of bumblebees have gone extinct in United Kingdom alone.

The reasons for a bee population's decline likely vary among species and habitats. Two agricultural activities could be extensively harming bumblebees, although the ramifications have yet to be adequately investigated in North America. Imported bees used for pollinating plants grown commercially in greenhouses are known to introduce diseases to their wild relatives. As well, a group of insecticides called neonicotinoids, that are highly toxic to bees, have been applied to North American crops since the early 1990s.