Wild bees disappearing from where they’re needed most

Where have all the wild bees gone? @bberwyn photo.
Where have all the wild bees gone? @bberwyn photo. @bberwyn photo.

New study to guide conservation and restoration efforts

Staff Report

A steep decline in wild bee populations could raise costs for farmers and potentially even destabilize the nation’s crop production, according to a new study that maps regional bee population trends.

The findings suggest wild bees are disappearing from many of the country’s most important farmlands, including California’s Central Valley, the Midwest’s corn belt, and the Mississippi River valley.

The research team, led by Insu Koh at the University of Vermont, estimates that wild bee abundance between 2008 and 2013 declined in 23 percent of the contiguous U.S. The study also shows that 39 percent of US 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.

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

The study comes after alarms were raised at the highest levels, including a 2014 White House memorandum that called for a national assessment of wild pollinators and their habitats. More than $3 billion of the US agricultural economy depends on the pollination services of native pollinators like wild bees.

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

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,” said 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.”

Koh said the new study helps map hotspots down to the county level to guide protection and restoration of wild bee habitat. Some of the area of greatest concern include places important for high-value specialty crops including 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.

Crops that are highly 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.

Along with threats from climate change, pesticides and diseases, the new study suggests habitat loss — by conversion to croplands — is another key factor in wild bee population declines.

In eleven key states where the new study shows bees in decline, the amount of land tilled to grow corn spiked by two hundred percent in five years, replacing grasslands and pastures that once supported bee populations.

“These results reinforce recent evidence that increased demand for corn in biofuel production has intensified threats to natural habitats in corn-growing regions,” the new study explained.

Over the last decade, honeybee keepers have lost many colonies and have struggled to keep up with rising demand for commercial pollination services, pushing up costs for farmers.

“When sufficient habitat exists, wild bees are already contributing the majority of pollination for some crops. Even around managed pollinators, wild bees complement pollination in ways that can increase crop yields,” said Neal Williams, a co-author on the study from the University of California, Davis.

“Most people can think of one or two types of bee, but there are 4,000 species in the U.S. alone,” said Ricketts. “Wild bees are a precious natural resource we should celebrate and protect. If managed with care, they can help us continue to produce billions of dollars in agricultural income and a wonderful diversity of nutritious food.”

“We can now predict which areas are suffering the biggest declines of wild bee abundance,” Koh said, “and identify those areas, with low bee supply and high bee demand, that are the top priority for conservation.”

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