Butterflies are disappearing in the United States. All kinds of them. With a speed scientists call alarming.

A sweeping new study published in the journal Science tallies, for the first time, butterfly data from more than 76,000 surveys across the continental United States. The results: From 2000 to 2020, the total butterfly abundance fell by 22% across the 554 species counted. That means that for every five individual butterflies within the contiguous U.S. in the year 2000, there were only four in 2020.

“Action must be taken,” said Elise Zipkin, a Red Cedar Distinguished Professor of quantitative ecology at Michigan State University and a co-author of the paper. “To lose 22% of butterflies across the continental U.S. in just two decades is distressing and shows a clear need for broad-scale conservation interventions.”

Zipkin, director of MSU’s Ecology, Evolution and Behavior Program, and her MSU colleague and co-author Nick Haddad, professor of integrative biology in EEB, have been major figures in assessing the state of U.S. butterflies. Zipkin, a formidable number cruncher, is known for gleaning hard facts from imperfect data sets to better understand the natural world.