University of Vermont (UVM) researchers have said that the disappearance of wild bees from farmlands is threatening crops all over the U.S., perfscience reports.

Wild bees are disappearing from substantial swathes of farmlands in the United States.

Wild bees play an important role in the pollination of crops. They provide an essential ecosystem service to natural as well as agricultural ecosystems. Fewer bees could mean having fewer crops and smaller amounts of agriculture produce.

For the study, UVM researchers tracked the wild bee populations in the agricultural regions of the country, including California and the southern Mississippi River Valley.

They concluded that nearly 39 per cent of crop areas were highly dependent on bees for pollination.

Taylor Ricketts, the director of UVM's Gund Institute, said,

"It's clear that pollinators are in trouble ... But what has been less clear is where they are in the most trouble - and where their decline will have the most consequence for farms and food."

The wild bee populations in the U.S have fallen by 23 per cent between 2008 and 2013, attributed to a destruction of their natural habitats.

The populations of the wild bees have declined also because of the increasing use of harmful pesticides, diseases and climate change.

The team of seven researchers, led by author Insu Koh, from the Gund Institute for Ecological Economics, University of Vermont studied bee habitation, land cover data and specialist knowledge to map U.S. bee trends and population.

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

"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," notes the study.

"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, as reported by University of California.