Butterflies are disappearing. Not just the rare and vulnerable ones but virtually all of them. And now, scientists have the data to prove just how bad it is.

A sweeping new study reveals that butterfly populations across the continental United States have plummeted by 22% over the past two decades. For every five butterflies that graced the skies in 2000, only four remain today.

The findings, based on an analysis of 12.6 million butterfly sightings from 76,000 surveys, paint a stark picture of decline. Nearly one-third of the 342 species studied lost more than half their populations. The decline is not evenly distributed, though. Some, like the West Virginia white and Julia’s skipper, have vanished by more than 90%. Even the West Coast lady, a once-common backyard butterfly, has declined by 80%.

“To lose 22 percent of butterflies across the continental U.S. in just two decades is distressing,” said Elise Zipkin, a quantitative ecologist at Michigan State University and co-author of the study.

“For those who were not already aware of insect declines, this should be a wake-up call,” said Collin Edwards, the study’s lead author.

A Nationwide Collapse

The new study is the most comprehensive of its kind. It combines data from 35 monitoring programs, including citizen science initiatives like the North American Butterfly Association’s Fourth of July counts. Researchers integrated decades of data, allowing them to track trends across regions and species. This ultimately revealed a widespread and alarming pattern of decline.

The causes driving this massive butterfly collapse are complex, but scientists have identified several key threats. Habitat loss—the result of urban sprawl and agriculture—has eliminated food sources and breeding grounds. Insecticides, particularly those applied preemptively to seeds, have likely dealt a silent but deadly blow. And climate change is warping ecosystems, making parts of the U.S. too hot and dry for many butterfly species to survive.

The Southwest, one of the country’s most arid regions, has been hit particularly hard. Butterflies have delicate bodies and are highly sensitive to drying out. As droughts intensify, these insects and their host plants suffer.

“Drought is a double threat,” said Eliza Grames, an assistant professor at Binghamton University. “It harms butterflies directly and also affects their food and host plants.”

Why Butterflies Matter

Butterflies are more than just pretty insects. Like bees, they are vital pollinators, allowing countless plants to spread and reproduce, including crops like cotton. In Texas alone, butterflies and flies are responsible for $120 million in cotton production annually. They also serve as a critical food source for birds, which have experienced parallel declines. Over the past 50 years, North America has lost nearly three billion birds — a rate eerily similar to the drop in butterfly populations.

This decline mirrors a larger crisis. Other insects, less studied than butterflies, are likely experiencing similar fates. Data from 166 long-term surveys across 1,676 sites reported in 2020 suggest a drop of 25% in insect numbers over the last 30 years, with Europe faring exceptionally worse. In 2022, British researchers analyzed about three-quarters of a million samples from around 6,000 sites for nearly 20,000 different species. They found insect numbers plunged by half in the most impacted parts of the world.

Despite the grim numbers, researchers emphasize that butterflies can recover if urgent action is taken. Unlike long-lived species that take decades to bounce back, butterflies reproduce rapidly. Give them the right conditions, and their populations can surge within a few years.

The endangered Karner blue butterfly was once on the brink, but it rebounded in New York’s Albany Pine Bush Preserve after conservationists restored its habitat. Similar efforts could help struggling species across the country.

Even small, individual actions can make a difference. Planting native wildflowers, avoiding insecticides, and leaving patches of backyard wild can help butterflies thrive.

“Insects are fundamental to life on Earth,” said Grames. “We need conservation actions and policies that support them.”

Scientists also stress the need for policy change. In some states, insects are not even classified as wildlife, leaving them unprotected. But laws can be rewritten. The U.S. Fish and Wildlife Service recently recommended listing the monarch butterfly as a threatened species, and researchers hope that new data will prompt protection for others.

“People depend on plants, microbes, and animals for the air we breathe, the water we drink, and the food we eat,” said Zipkin. “Yet we are losing species at rates that rival the major mass extinction events on our planet.”

The findings appeared in the journal Science.