Study Pinpoints Where Wild Bee Declines Will Most Affect Farmers

Researchers at the University of Vermont and other institutions have identified 139 U.S. counties where wild bee declines could have the most troubling impact on agriculture. Leif Richardson/University of Vermont

As the number of wild bees drops dramatically in the United States, new research indicates where farmers will likely suffer the most. A study published Monday in the journal Proceedings of the National Academy of Sciences identified 139 counties across the country where the "mismatch" between demand for wild bees and supply is most troubling.

In the continental U.S., the wild bee population declined 23 percent between 2008 and 2013, according to the study. Of the cropland that depends on pollinators, the researchers found, 39 percent falls in the "mismatched" areas.

The study's goal wasn't focused on mapping where bees are most in decline, but rather to identify where farmers would be most affected. Researchers from the University of Vermont, Franklin and Marshall College, the University of California at Davis and Michigan State University believe the study is the first to map national bee population and agricultural trends side by side.

To create the map, the researchers first identified areas of farmland and then sought out information about the quality of nesting and flower resources in those areas and how far bees can travel.

According to the study, the demand for wild bees is "mismatched" with the supply of bees in 39 percent of pollinator-dependent crop areas in the U.S. University of Vermont

"What produces is a map of tiny square by tiny square, a prediction from this model about the abundance of bees," says senior author Taylor Ricketts, a professor at the University of Vermont and director of its Gund Institute for Ecological Economics. Ricketts and the other authors then compared that abundance map to maps for where the demand for wild bees is highest, given which crops most rely on pollinators. "What we came up with are the 139 counties that seem to have worrisome mismatches between the trend and the supply, or the abundance of bees and the demand."

According to the study, those "mismatches" hit farmers particularly hard in 11 states: Illinois, Kansas, Louisiana, Minnesota, Missouri, Nebraska, North Dakota, Oklahoma, South Dakota, Texas and Wisconsin. Crops that depend most on pollinators include almonds, apples, blueberries, peaches, pumpkins and watermelons. Crops such as soybeans, canola and cotton are less dependent.

The researchers' most troubling discovery, Ricketts says, is that the crops that need pollinators the most seem to grow in places with the fewest wild bees.

Last year, the White House established a task force to investigate why bees and other pollinators are dying off. Many pollinator experts believe pesticides and habitat loss are among the reasons. In May, the government announced the results of the task force, including a plan to set aside 7 million acres as habitats for pollinators. The U.S. Department of Agriculture also now encourages farmers to set aside land for that purpose.

The importance of bees to farming is likely why the government is so concerned; according to the study, more than $3 billion of the country's agricultural gross domestic product relies on wild pollinators. Another $11.53 billion relies on non-wild bees.

"Obama put this on the national stage," Ricketts says. "What this study does is literally put this issue on the map. It's a map of where we should focus those efforts he's calling for."