Pollinators, including some 20,000 species of wild bees, contribute to the growth of fruit, vegetables and many nuts, as well as flowering plants. Plants that depend on pollination make up 35 percent of global crop production volume with a value of as much as $577 billion a year. The agricultural system, for which pollinators play a key role, creates millions of jobs worldwide.

Many pollinator species are threatened with extinction, including some 16 percent of vertebrates like birds and bats, according to the document. Hummingbirds and some 2,000 avian species that feed on nectar spread pollen as they move from flower to flower. Extinction risk for insects is not as well defined, the report notes, but it warned of “high levels of threat” for some bees and butterflies, with at least 9 percent of bee and butterfly species at risk.

The causes of the pressure on these creatures intertwine: aggressive agricultural practices that grow crops on every available acre eliminate patches of wildflowers and cover crops that provide food for pollinators. Farming also exposes the creatures to pesticides, and bees are under attack from parasites and pathogens, as well.