A U.N. sponsored report warns that too many species of pollinators are nearing extinction. These are bees, butterflies, even some birds and 20,000 other species that are crucial to the world's food supply.

WASHINGTON — Many species of wild bees, butterflies and other critters that pollinate plants are shrinking toward extinction, and the world needs to do something about it before our food supply suffers, a new United Nations scientific mega-report warns.

The 20,000 or so species of pollinators are key to hundreds of billions of dollars’ worth of crops each year — from fruits and vegetables to coffee and chocolate. Yet 2 out of 5 species of invertebrate pollinators, such as bees and butterflies, are on the path toward extinction, said the first-of-its-kind report. Pollinators with backbones, such as hummingbirds and bats, are only slightly better off, with 1 in 6 species facing extinction.

“We are in a period of decline and there are going to be increasing consequences,” said report lead author Simon Potts, director of the Centre for Agri-Environmental Research at the University of Reading in England.

And it’s not just honeybees. In some aspects they’re doing better than many of their wild counterparts, like the bumblebee, despite dramatic long-term declines in the United States and a mysterious disorder that has waned.

The trouble is the report can’t point to a single villain. Among the culprits: the way farming has changed so there’s not enough diversity and wild flowers for pollinators to use as food; pesticide use, including a controversial one, neonicotinoid, that attacks the nervous system; habitat loss to cities; disease, parasites and pathogens; and global warming.

The report is the result of more than two years of work by scientists across the globe who got together under several different U.N. agencies to come up with an assessment of Earth’s biodiversity, starting with the pollinators.