Study raises the possibility of a country without butterflies

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.

Elise Zipkin, Michigan State University

“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.

Haddad is a terrestrial ecologist — a scientist on the ground specializing in the fates of the most fragile and rare butterfly populations. The widespread decline of butterflies found in this study has shaken Haddad, and he reports that the mountain of data is on display in his own Michigan neighborhood.

Nick Haddad, Michigan State University

“My neighbors notice it,” Haddad said. “Unprompted, they’ll say, ‘I’m seeing fewer butterflies in my garden; is that real?’ My neighbors are right. And it’s so shocking.”

In this paper, Zipkin and Haddad were among a working group of scientists with the USGS Powell Center for Analysis and Synthesis that aggregated decades of butterfly data from 35 monitor programs that included records of over 12.6 million butterflies. Using data integration approaches, the team examined how butterfly abundances changed regionally and individually for the 342 species with enough data.

Abundance is a term that threatens to become ironic. Butterfly populations dropped an average of 1.3% annually across the country, except for the Pacific Northwest. But even that encouraging result came with a caveat. Further scrutiny of the apparent 13.8% increase in overall abundance in the Pacific Northwest over the 20-year study period was credited largely to the California tortoiseshell butterfly, which was enjoying a population boom not expected to be sustained.

Butterflies are the most surveyed insect group, courtesy of extensive volunteer-based and expert science monitoring programs. Until now, studies have focused on individual species — most notably monarch butterflies — or limited to specific locations.

This new study uses all the available regional butterfly monitoring data within the continental United States and then develops a method of analysis that appropriately accounts for variations in collection protocols across programs and regions to produce comparable results for hundreds of species.

“This is the definitive study of butterflies in the U.S.,” said the study’s lead author, Collin Edwards, previously a postdoctoral research associate at Washington State University Vancouver who now works at the Washington Department of Fish and Wildlife. “For those who were not already aware of insect declines, this should be a wake-up call. We urgently need both local- and national-scale conservation efforts to support butterflies and other insects. We have never had as clear and compelling a picture of butterfly declines as we do now.”

Edwards had been a postdoctoral research associate at Washington State University, Vancouver, and now works at the Washington Department of Fish and Wildlife.

The results reveal that 13 times as many species declined as increased — with 107 species losing more than half their populations. 

Zipkin and Haddad say butterflies are more than fluttering symbols of freedom and beauty. They play important roles in cycling nutrients and are a significant food source for other organisms such as birds. Over the last 50 years, North America has lost nearly 3 billion birds, a decline that nearly matches that of the butterflies. 

Butterflies are important and often overlooked pollinators. People tend to think of bees first, but butterflies (and flies) are responsible for $120 million of cotton production in Texas, for example.

Zipkin said she sees this paper as an important heads-up to the country’s policymakers. “People depend on plants, microbes and animals for the air we breathe, the water we drink and the food we eat. Yet, we are losing species at rates that rival the major mass extinction events on our planet,” Zipkin said. “The U.S. plays an important role in setting policies and creating laws that conserve and protect biodiversity from local to global scales. Our leaders and the federal government, in particular, are responsible for making sure future generations have the necessary resources to thrive.”

Last year, Haddad was part of a study published by the journal PLOS ONE that pinpointed the danger of insecticides, which rose above other threats such as habitat loss and climate change in reducing butterfly abundance and diversity. He points out that saving butterflies isn’t a hopeless problem, just one that requires will.

A lot of insecticide use, he said, lacks strategy and results in overuse. Some 20% of cropland suffers from poor yields. Creating policies that return under-producing land to nature could help the butterflies rally.

“Prophylactic and near-universal application of insecticides harms butterflies and other beneficial insects, with no proven benefit to crop yield,” Haddad said. “What is applied as ‘insurance’ is extracting a great debt to agroecosystems. The good news is that the widespread application of insecticides can be reversed, and butterflies and other pollinators will recover.”

In addition to Zipkin, Haddad, and Edwards, “Rapid butterfly declines across the United States during the 21st century” was written by Erica Henry (Washington State University-Vancouver), Matthew Forister (University of Nevada-Reno), Kevin Burls (Xerces Society for Invertebrate Conservation), Steven Campbell (Albany Pine Bush Preserve Commission), Elizabeth Crone (University of California-Davis), Jay Diffendorfer (U.S. Geological Survey Geosciences and Environmental Change Sciences Center), Margaret Douglas (Dickinson College), Ryan Drum (U.S. Fish and Wildlife Service), Candace Fallon (Xerces Society for Invertebrate Conservation), Jeffrey Glassberg (North American Butterfly Association and Rice University), Eliza Grames (Binghamton University), Rich Hatfield (Xerces Society for Invertebrate Conservation), Shiran Hershcovich (Butterfly Pavilion), Scott Hoffman-Black (Xerces Society for Invertebrate Conservation), Elise Larsen (Georgetown University), Wendy Leuenberger (Michigan State University), Mary Linders (Washington Department of Fish and Wildlife), Travis Longcore (University of California-Los Angeles), Daniel Marschalek (University of Central Missouri), James Michielini (University of California-Davis), Naresh Neupane (Georgetown University), Leslie Ries (Georgetown University), Arthur Shapiro (University of California-Davis), Ann Swenger (Independent Researcher), Scott Swengel (Independent Researcher), Douglas Taron (Chicago Academy of Science, and Peggy Notebaert Nature Museum), Braeden Van Deynze (Washington Department of Fish and Wildlife), Jerome Wiedmann (Ohio Lepidopterists), Wayne Thogmartin (U.S. Geological Survey Upper Midwest Environmental Sciences Center), and Cheryl Schultz (Washington State University-Vancouver).

Zipkin and Haddad are members of MSU’s Ecology, Evolution and Behavior Program, of which Zipkin is director.