A country without butterflies: Rapid decline in U.S. populations

Butterflies are currently disappearing in the United States with alarming speed. A new study estimates that overall butterfly abundance in the continental United States dropped by 22% between 2000 and 2020. 

Researchers warn that without immediate action, these vibrant insects – essential for pollination, nutrient cycling, and food webs – could continue to vanish at a rate with unsettling consequences for ecosystems and agriculture alike.

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

Largest-ever compilation of butterfly data

In the past, scientists have typically focused on one species (like the monarch) or on a limited geography. This study, however, brings together more than 76,000 surveys of butterfly populations spanning the lower 48 states. 

The researchers incorporated data from 35 separate monitoring programs and compiles records of over 12.6 million butterflies, enabling analysts to develop a nationwide snapshot of butterfly abundance trends and species richness.

To clarify changes, the research team examined 554 different species, comparing population sizes in 2000 with those in 2020. They discovered that for every five butterflies present at the start of the century, only four remained after two decades. 

The average annual decline of 1.3% highlights the widespread nature of the downturn, with fewer butterflies appearing in backyards, open meadows, and nearly everywhere in between.

Increasing decline of butterflies

Nick Haddad, a professor of integrative biology at Michigan State and one of the study’s co-authors, has been closely involved in charting the precarious state of U.S. butterflies. He combines scientific expertise with a practical, on-the-ground perspective. 

While many declines involve species we rarely encounter, Haddad stresses that losses can also be noticed close to home.

“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.”

Such observations confirm broader findings: average people are detecting changes in butterfly abundance without relying on official numbers. Now, large-scale data affirm that this anecdotal evidence reflects a genuine, countrywide shift.

The definitive study on U.S. butterflies

“This is the definitive study of butterflies in the U.S.,” said Collin Edwards, the study’s lead author. “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, formerly a postdoctoral research associate at Washington State University, Vancouver, now works with the Washington Department of Fish and Wildlife. 

He and his colleagues designed methods to integrate sometimes-variable data sets. By analyzing changes in “butterfly abundances, they aimed to see how species fared individually, regionally, and collectively.

Though the Pacific Northwest seemed to buck the national trend by showing a 10% overall gain in butterfly numbers, that apparent uptick is traced mainly to a single species, the California tortoiseshell, which had a population spike unlikely to last. 

Elsewhere, the standard pattern of decline holds true, demonstrating that the national losses are part of a deeper, multi-regional shift.

Urgent need for solutions

By studying 554 species, the team highlights just how widespread the problem is. Many species had never been systematically analyzed at such a scale. The numbers show that 13 times more species declined than increased, with 107 species losing over half their populations.

According to Zipkin and Haddad, butterflies are more than fluttering symbols of freedom and beauty. They serve as pollinators – alongside bees and flies – supporting a portion of the country’s agriculture and a source of food for numerous animals, including birds. 

Indeed, bird populations have dropped by nearly three billion over the last 50 years, at a rate that parallels butterfly declines.

The researchers highlight that policymakers and the public should view these insects not just as ornaments but as key contributors to ecological balance. 

If butterflies continue to disappear, pollination services may weaken, predator-prey relationships will be altered, and many plants reliant on butterfly pollination could suffer.

Lessons from past findings 

Haddad’s earlier work, published in 2024 in PLOS ONE, determined that insecticide use was a leading cause of butterfly mortality. Although habitat destruction and climate change are also major factors, the findings suggest that widespread pesticide application does extraordinary harm. 

Profligate use of insecticides – often deployed as a sort of “insurance” by farmers – can, ironically, result in minimal gains in crop yields while doing maximum damage to insect populations.

Haddad believes that a shift to more strategic, evidence-based pesticide use would give many butterfly species a fighting chance to rebound.

Slowing the decline of butterflies

Zipkin describes the current data as a strong warning to national leaders: “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,” she said.

Zipkin said that the United States can take meaningful steps, from local habitat management to large-scale legislative action, to protect not just butterflies but the biodiversity that underpins human health and well-being. 

Edwards hopes individuals and local governments will commit resources to planting pollinator-friendly vegetation, curtailing pesticide use, and supporting land conservation measures.

While time is short, the researchers remain cautiously optimistic: the data highlight just how urgent the task is, but it also provides a roadmap for remedying the losses. 

Through improved policy, targeted restoration programs, and mindful insecticide management, the decline of these “fluttering symbols” might be slowed, or even reversed – restoring butterflies to gardens, fields, and wildlands across the nation.

The study is published in the journal Science.

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