Butterflies, known for their beauty and vital role in pollination, are vanishing from U.S. landscapes at an alarming rate. A comprehensive study, published Thursday in the journal Science, found that 22% of butterflies in the United States disappeared between 2000 and 2020.
The new research offers a stark warning about the potential future of these cherished insects.
“Losing one out of every five butterflies over 20 years should be a big wake-up call to people,” said Dr. Eliza Grames, an assistant professor of biological sciences at Binghamton University and co-author of the study. “These declines are not stopping.”
While butterflies are the most extensively monitored insect group in the U.S., most past studies have been limited by geography or focused on specific species, a news release on the study said. The researchers behind the Science study used data from more than 12.6 million butterflies spanning 342 individual species, drawing from 76,000 surveys across 35 nationwide monitoring programs.
Funded by the U.S. Geological Survey, the study was the first to integrate such a vast dataset, its authors said. The findings revealed that 33% of butterfly species have experienced significant population declines over the past two decades, with 107 out of the 342 species examined losing more than half of their population — including 22 species that declined by more than 90%. Meanwhile, only 3% of species showed population increases.
One of the most striking examples is the monarch butterfly. In December 2024, the U.S. Fish and Wildlife Service proposed listing the monarch under the Endangered Species Act, saying the species’ eastern population has declined by about 80% and the western population has dropped by more than 95% since the 1980s.
The species was already designated an endangered species by the International Union for the Conservation of Nature in 2022.
Ultimately, the butterfly decline is part of a larger global trend of insect population loss, with insects declining by about 1-2% annually, the study’s authors said.
Butterflies play an essential role in ecosystems, pollinating flowers, crops, and other plants. Their decline could have far-reaching impacts on plant reproduction and the health of ecosystems.
According to the Science study, habitat loss, climate change, and pesticide use are driving their declines. Rising temperatures and changing climates threaten butterfly populations by disrupting breeding cycles, reducing food sources, and increasing habitat stress. Insecticides have been identified as leading causes of butterfly decline, which can be tackled with policy intervention such as restricting harmful insecticides, promoting integrated pest management and encouraging diversified cropping, according to the study.
Despite the declines, individuals can take steps to help butterfly populations recover, Grames said.
“One of the really positive messages about insect conservation is that the things we do in our own backyards actually make a difference,” she said.
She recommends allowing a portion of yards to grow wild with native plants, reducing pesticide use, and creating habitat spaces like small brush piles for insects. “Even simple actions — like leaving a strip of wildflowers or planting species that support pollinators — can provide crucial resources for butterflies and other insects.”
On a larger scale, experts say conservation efforts, including habitat preservation and climate adaptation strategies, are also essential to protecting vulnerable species and ensuring butterfly populations remain resilient in the face of ongoing environmental changes.
