Butterflies vanishing at “catastrophic” rate, insecticides a major culprit
By isabelle // 2025-03-10
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  • Butterfly populations in the U.S. have declined by 22% over 20 years, with 114 species experiencing significant drops.
  • Insecticides, particularly neonicotinoids, are a major driver of the decline, harming biodiversity and ecosystems.
  • The Southwest U.S. saw the most severe losses, with butterfly populations dropping by over 50% in some states.
  • Butterflies are vital pollinators, and their decline threatens food systems, wildlife, and ecological balance.
  • Experts urge immediate action, including reducing pesticide use, restoring habitats, and promoting public conservation efforts.
America’s butterflies are disappearing at an alarming rate, with populations declining by 22% over the past two decades, according to a groundbreaking study published in the journal Science. The research, which analyzed data from 76,957 surveys across the lower 48 states, reveals a troubling trend: for every five butterflies present in 2000, only four remain today. This dramatic decline, described as “catastrophic” by experts, threatens not only the beauty of these iconic insects but also the health of ecosystems and agriculture nationwide. The study, the first of its kind to provide a comprehensive national analysis, found that 114 butterfly species experienced significant population drops, while only nine saw increases. Iconic species like the monarch butterfly, once numbering 1.2 million in 1997, have plummeted to an all-time low of fewer than 10,000. “Losing one out of every five butterflies over 20 years should be a big wake-up call to people,” said Dr. Eliza Grames, a co-author of the study and assistant professor at Binghamton University. “These declines are not stopping.”

The role of insecticides

While habitat loss and other factors contribute to the decline, researchers point to insecticides as a primary driver. A separate study published in PLOS ONE found that the widespread use of neonicotinoid-treated seeds and other chemical pesticides is strongly linked to an 8% decline in butterfly species diversity across the Midwest. Nick Haddad, a professor at Michigan State University and co-author of the Science study, emphasized that insecticides are causing “extraordinary harm” to butterfly populations. “It makes sense because insecticide use has changed in dramatic ways in the time since our study started,” Haddad said. He added that the minimal gains in crop yields that farmers see from using these chemicals is destroying insect life. The PLOS ONE study, which analyzed 17 years of data, found that insecticides—not herbicides or climate change—were the strongest factor in monarch butterfly declines. “Butterflies are key indicators of broader insect decline,” Haddad added. “The implications of our findings for conservation will extend to the entire insect world.” The decline is not limited to one region. While the Pacific Northwest saw a 10% increase in butterfly numbers—driven largely by a temporary spike in the California tortoiseshell population—the Southwest experienced the most severe losses. States like Arizona, New Mexico, Texas, and Oklahoma saw butterfly populations drop by more than half over two decades. David Wagner, an entomologist at the University of Connecticut, called the findings “catastrophic and saddening.” He warned that the annual decline of 1.3% may seem small, but over time, it adds up to devastating losses. “In just 30 or 40 years, we are talking about losing half the butterflies over a continent,” Wagner said. “The tree of life is being denuded at unprecedented rates.”

Why butterflies matter

Butterflies are more than just symbols of beauty and freedom. They play a critical role in pollination, supporting crops and maintaining ecological balance. Their decline could have cascading effects on food systems and wildlife, including birds, which have also seen significant population drops in recent decades. “Butterflies are an ambassador for nature’s beauty, fragility, and the interdependence of species,” said Anurag Agrawal, a butterfly expert at Cornell University. “Their loss is a warning sign for the health of our ecosystems.” Researchers urge immediate action to curb the decline, including stricter regulation of insecticides, habitat restoration, and public education. Elise Zipkin, a professor at Michigan State University and co-author of the Science study, stressed the need for “broad-scale conservation interventions.” "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." Although the situation is dire, experts remain cautiously optimistic. By reducing pesticide use, planting pollinator-friendly vegetation, and supporting conservation efforts, individuals and policymakers can help reverse the trend. “You can make changes in your backyard, and in your neighborhood, and in your state,” Haddad said. “That could really improve the situation for a lot of species.” The disappearance of butterflies is more than an ecological crisis—it’s a call to rethink how we interact with the natural world. Without swift action, the fluttering symbols of summer may become a rare sight, leaving ecosystems and agriculture vulnerable in their absence.   Sources for this article include: KOMONews.com Earth.com Phys.org CANR.MSU.edu
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