RUTGERS (US) — Wild pollinators are just as important, and often more efficient, at pollinating crops than domestic honey bee colonies, but bumble bee colonies are vanishing.
“This will be a surprise to the agricultural establishment,” says Rachael Winfree, professor of ecology, evolution, and natural resources in Rutgers’ School of Environmental and Biological Sciences, who was involved in the two new studies.
“There’s a widespread assumption that domestic honeybees are doing the job. This work shows that’s not true.”
The first study, published in Science, involved researchers from every continent but Antarctica, who visited 600 fields in which 41 varieties of crop were growing.
About 75 percent of food crops require pollination, making pollinators an essential part of food security. The researchers found that almost half that pollination is the work of wild pollinators, primarily wild bees, flies, and other insects.
The good news is that farmers can keep wild pollinators abundant by leaving a bit of natural habitat around their fields—patches of wildflowers, some hedgerows, or anything that gives wild bees a place to live, Winfree says.
“Farms with a little bit of natural habitat are more sustainable in terms of their pollination,” she says. She adds that farms using pesticides and insecticides tend to have fewer pollinators than those that don’t.
Bumble bee losses
The second study, published in Proceedings of the National Academy of Sciences, examines historical changes in the population of wild bees in the northeastern United States and southern Canada. Winfree and colleagues used web-based software to compile 30,000 museum specimen records representing 438 bee species.
The researchers looked at “species richness”—the number of species of bee in a specific region—and how it changed over time. They used museum records that go back to 1872.
They found that wild bees as a whole had suffered some species losses but that these declines were moderate—about 15 percent of the more than 400 species over the 140 years.
Bumble bee colonies, on the other hand, are disappearing. Since 1872, according to the PNAS study, the number of bumble bee species in the northeastern United States and southern Canada has declined about 30 percent.
Winners and losers
Since, as Winfree and her many co-authors find in the Science paper, wild pollinators are key to successful pollination of agricultural crops, a 30 percent loss in species richness is bad news. This is especially true of bumble bees. “They’re very important,” Winfree says. “They’re big and hairy and carry a lot of pollen.”
While the PNAS paper doesn’t offer reasons for the loss in species richness for bumble bees or other bees, the authors point out that non-native species of wild bees seem to be doing better than those native to North America. There is some indication that climate change may play a role, since bees long associated with the south seem to be moving north.
“Environmental change affects species differentially,” says Ignasi Bartomeus, a former member of Winfree’s lab and now a postdoctoral scholar at the Swedish University of Agricultural Sciences in Stockholm.
“It creates ‘losers’ that decline with increased human activity, but also ‘winners’ that thrive in human-altered environments.”
Additional researchers from University of Leeds, Michigan State University, University of Queensland, and Cornell University contributed to the paper in Science, among others. The paper in PNAS includes additional authors from Rutgers and Cornell University.