Butterfly Populations in the U.S. Plummet by 22% Over Two Decades, Study Reveals
A recent study has uncovered a startling decline in butterfly populations across the United States, with numbers dropping by more than a fifth between 2000 and 2020.
Researchers from Binghamton University in New York found that butterfly populations shrank by 22% during this period. Alarmingly, a third of all studied species faced severe reductions, with some—such as Julia's Skipper—experiencing catastrophic losses of over 90%.
Despite these declines, scientists suggest that targeted conservation efforts could help butterflies recover.
Tracking the Decline: A Massive Data Analysis
The study, published in Science, assessed butterfly abundance—the total number of individuals in a given area. To conduct their analysis, researchers examined 12.6 million butterfly observations collected from 76,000 surveys across 35 monitoring programs.
Data was sourced from multiple initiatives, including citizen science efforts like the North American Butterfly Association’s Fourth of July counts. By applying statistical modeling, scientists estimated population trends for 342 butterfly species.
Findings revealed that 33% of species were experiencing significant declines, with some suffering drastic reductions—107 species had lost more than half of their population.
"While the results aligned with global trends, seeing the extent of the decline at such a large spatial scale was sobering," stated Professor Eliza Grames, an assistant professor of biological sciences at Binghamton University.
Most Severely Affected Butterfly Species
Among the species facing the sharpest declines are the Florida white, Hermes copper, tailed orange, Mitchell's satyr, and West Virginia white—all of which have lost over 98% of their populations within the United States.
Even once-common species are struggling. The West Coast lady, a butterfly frequently seen in backyards, has declined by 80%, raising concerns about the vulnerability of more adaptable species.
"That's alarming because it suggests even common butterflies aren't safe," said Prof. Grames.
Causes of the Butterfly Decline
Researchers attribute the plummeting numbers to habitat destruction, pesticide use, and climate change. Butterflies play a crucial role as pollinators, contributing to plant and crop growth. Their decline could disrupt ecosystems and impact food production.
Beyond their role in pollination, butterflies also serve as environmental indicators. A drop in their population often signals broader ecological imbalances.
Southwest U.S. Hit the Hardest
The study found that butterfly populations in the Southwest U.S.—one of the nation’s hottest and driest regions—were experiencing the most severe declines. Scientists believe drought is a key factor driving these losses.
"Drought is a double threat - it harms butterflies directly and also affects their food and host plants," Prof. Grames explained.
The research may influence conservation efforts by helping identify which species need urgent protection under the International Union for Conservation of Nature (IUCN) Red List and the U.S. Endangered Species Act.
A Path to Recovery
Despite the concerning trends, scientists remain optimistic about butterfly populations bouncing back.
"Butterflies can recover quickly because they have short generation times. Small actions like planting wildflowers, reducing pesticide use, or even leaving part of a backyard unmowed can significantly improve their chances," Prof. Grames said.
She also emphasized the need for government involvement in conservation efforts.
"Insects are fundamental to life on earth, and we need conservation actions and policies that support insects."
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