The Western bumble bee, once easily spotted in California, could not be found in a recent survey led by the University of California-Riverside (UCR). The first statewide census of California bumble bees in 40 years found several other species absent, as well. UCR entomologist Hollis Woodard’s research group collected bees from 17 sites representing six different ecosystems previously known to host a large variety of bumble bees, as documented in the journal Ecology and Evolution. One of the missing species, the Western bumble bee, is an important pollinator of wild plants and crops. “We didn’t find it, even once,” says Woodard.

This study was an effort to document changes in bumble bee populations across large geographic areas in California since the last one in the 1980s. Smaller-scale studies have documented significant declines in bumble bee populations around the world due to climate change, development of wild habitat and the use of bee-killing pesticides, so it is important to have data that documents bee health. Bumble bees can fly in cooler temperatures and lower light levels than many other bees, helping to pollinate crops worth $3 billion annually in the U.S., including tomatoes, peppers and cranberries.