Wild bee populations in parts of the United States are declining, largely due to habitat loss in areas with intense farming.
Many studies have focused on the pollination and population patterns of domesticated honeybees. But like honeybees, wild bees are important pollinators of food crops. Dropping populations of wild bees in agricultural areas could affect crop pollination and result in higher costs for farmers, researchers report December 21 in the Proceedings of the National Academy of Sciences.
Ecologist Taylor Ricketts of the University of Vermont in Burlington and colleagues used land-use databases and input from bee experts to create a map of where wild bees were more and less abundant in the United States from 2008 to 2013. The scientists found that wild bee populations declined in 23 percent of the contiguous United States. Areas with the lowest relative wild bee abundance were those with the most agriculture, in the Midwest’s Corn Belt and California’s Central Valley, for instance.
These areas of mismatch, which include farms that grow fruits and nuts, produce 39 percent of crops in the United States that depend on pollinators. A lack of wild bees could increase costs for farmers who will need to truck in domesticated honeybees to pollinate crops or face lower food yields, Ricketts says.
Creating wild bee habitat on field edges could help maintain wild bee populations and sustain crop pollination, he says. “You grow more abundant bees of diverse kinds and they spill out into your fields.”
Wild bee abundance varied in the United States from 2008 to 2013. Lighter regions, where there is more agriculture, have fewer wild bees, while the darker regions have more wild bees.