The first national study to map U.S. wild bees suggests they’re disappearing in many of the country’s most important farmlands, including California’s Central Valley, the Midwest’s corn belt and the Mississippi River valley.

UVM researchers Insu Koh (right) and Taylor Ricketts

If losses of these crucial pollinators continue, the new nationwide assessment indicates that farmers will face increasing costs and that the problem may even destabilize the nation’s crop production.

The findings were published on Dec. 21 in the Proceedings of the National Academy of Sciences.

The research team, led by Insu Koh at the University of Vermont (UVM), estimates that wild bee abundance between 2008 and 2013 declined in 23% of the contiguous U.S.

The study also shows that 39% of U.S. croplands that depend on pollinators — from apple orchards to pumpkin patches — face a threatening mismatch between rising demand for pollination and a falling supply of wild bees.

In June 2014, the White House issued a presidential memorandum warning that "over the past few decades, there has been a significant loss of pollinators, including honey bees, native bees, birds, bats, and butterflies."

The memo noted the multi-billion dollar contribution of pollinators to the U.S. economy, and called for a national assessment of wild pollinators and their habitats.

"Until this study, we didn’t have a national mapped picture about the status of wild bees and their impacts on pollination," says Koh, a researcher at UVM’s Gund Institute for Ecological Economics.

He added this was despite the fact that each year more than US$3 billion of the U.S. agricultural economy depends on the pollination services of native pollinators like wild bees.

The report that followed the White House memo called for seven million acres of land to be protected as pollinator habitat over the next five years.

"It’s clear that pollinators are in trouble," says Taylor Ricketts, the senior author on the new study and director of UVM’s Gund Institute.

"But what’s been less clear is where they are in the most trouble — and where their decline will have the most consequence for farms and food."

"Now we have a map of the hotspots," adds Koh.

"It’s the first spatial portrait of pollinator status and impacts in the U.S.," — and a tool that the researchers hope will help protect wild bees and pinpoint habitat restoration efforts.

The new study identifies 139 counties in key agricultural regions of California, the Pacific Northwest, the upper Midwest and Great Plains, west Texas, and the southern Mississippi River valley that have the most worrisome mismatch between falling wild bee supply and rising crop pollination demand.

These counties tend to be places that grow specialty crops — like almonds, blueberries and apples — that are highly dependent on pollinators, or they are counties that grow less dependent crops — like soybeans, canola and cotton — in very large quantities.

Of particular concern, the study shows that some of the crops most dependent on pollinators — including pumpkins, watermelons, pears, peaches, plums, apples and blueberries — have the strongest pollination mismatch, with a simultaneous drop in wild bee supply and increase in pollination demand.

"These are the crops most likely to run into pollination trouble, whether that’s increased costs for managed pollinators, or even destabilized yields," Taylor Ricketts says.

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