A national study to map the U.S. wild bee population, published in the Proceedings of the National Academy of Sciences, specifies that pollinators are in trouble and are being removed from farmlands. The researchers created new maps by identifying forty-five land-use types from two federal land databases, including both croplands and natural habitats.
“We can now predict which areas are suffering the biggest declines of wild bee abundance,” said Insu Koh, “and identify those areas, with low bee supply and high bee demand, that are the top priority for conservation.”
The White House in 2014 issued recommendations through a pollinator task force and 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 study also shows that 39% 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.
“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–even though each year more than $3 billion of the US agricultural economy depends on the pollination services of native pollinators like wild bees.
“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.”
“Now we have a map of the hotspots,” said 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 study revealed 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,” says Taylor Ricketts, “whether that’s increased costs for managed pollinators, or even destabilized yields.”
The researchers recommended seven million acres of land to be protected as pollinator habitat over the next five years. 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. Pollinators natural habitat in corn-growing regions have been replaced by increased demand for corn in biofuel production.
“By highlighting regions with loss of habitat for wild bees, government agencies and private organizations can focus their efforts at the national, regional, and state scales to support these important pollinators for more sustainable agricultural and natural landscapes,” said Michigan State University’s Rufus Isaacs, one of the co-authors on the study and leader of the Integrated Crop Pollination Project, a USDA-funded effort that supported the new research.
“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 Taylor Ricketts, Gund Professor in UVM’s Rubenstein School of Environment and Natural Resources. “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.”
Insu Koh, Eric Lonsdorf, Neal Williams, Claire Brittain, Rufus Isaacs, Jason Gibbs and Taylor Ricketts. Modeling the Status, Trends, and Impacts of Wild Bee Abundance in the United States. Proceedings of the National Academy of Sciences, December 2015 DOI: 10.1073/pnas.1517685113