Butterflies, with their delicate wings and vibrant colors, have long fascinated humans, serving as symbols of transformation, beauty, and ecological harmony. Their presence in gardens and wild landscapes adds an aesthetic charm, but beyond their visual appeal, butterflies play a crucial role in maintaining biodiversity. These insects act as pollinators, helping flowers reproduce and contributing to healthy ecosystems. However, alarming new research led by faculty members at Binghamton University, State University of New York, suggests that butterfly populations across the United States are experiencing a significant decline, raising concerns about broader environmental challenges.
A groundbreaking study published in Science provides the most comprehensive analysis of butterfly populations in the U.S. to date. Analyzing data from 76,000 surveys conducted over two decades, researchers discovered a stark reality: butterfly abundance declined by 22% between 2000 and 2020. This means that for every five butterflies present at the turn of the century, only four remained by 2020. The study, which compiled data from 35 monitoring programs encompassing over 12.6 million butterfly records, offers an unprecedented look at how these essential insects are faring across different regions and species.
Eliza Grames, an assistant professor of biological sciences at Binghamton University and co-author of the study, emphasized the significance of this large-scale analysis. “This was the most comprehensive analysis of butterflies in the U.S. and at such a big spatial scale,” she said. Unlike previous monitoring efforts that relied primarily on volunteer-driven citizen science programs focusing on individual species or specific locations, this research integrates data from numerous sources to create a more holistic view of butterfly population trends.
One of the study’s key findings is that one-third of butterfly species in the U.S. showed significant declines in abundance. Among these, 107 species experienced a population drop of more than 50%. The term “abundance” refers to the total number of individuals of a species in a given area, and these declines suggest that certain butterfly populations are at risk of severe depletion, or even local extinction, if conservation measures are not taken.
To conduct this large-scale analysis, Grames played a crucial role in generating range maps for butterfly species. These maps were instrumental in ensuring data accuracy, as they helped researchers determine whether recorded observations were reliable or required verification. “We didn’t have maps for where many of the butterflies were,” Grames explained. “How do we know which records are good? A bunch of them come from iNaturalist, a citizen science platform where anybody can upload pictures of species. But sometimes people go to a butterfly house and start recording all of these tropical species in, say, Colorado, which throws off the data.” By carefully examining spatial patterns, the research team was able to refine their dataset and ensure that their findings reflected genuine trends in butterfly populations.
One of the most concerning aspects of the study is the variation in drivers of butterfly decline across different regions of the United States. While many factors contribute to these declines, regional differences highlight the complexity of the issue. In the Midwest, for example, pesticide use has emerged as a major factor impacting butterfly populations. In contrast, in the Southwest, drought conditions pose a significant threat, while in the Northeast, climate change is having a pronounced effect. These regional stressors underscore the need for targeted conservation efforts that address the specific threats faced by butterfly species in different parts of the country.
The implications of butterfly decline extend far beyond the loss of these beautiful insects. Butterflies are crucial pollinators, aiding in the reproduction of many flowering plants and crops. Their decline could have cascading effects on ecosystems, impacting food chains and plant populations. Additionally, butterflies serve as indicator species, meaning their health reflects broader environmental changes. A decline in butterflies signals deeper ecological disruptions that could also be affecting other insect populations.
Recognizing the urgency of conservation efforts, researchers and students at Binghamton University are actively working on assessments that could help protect endangered butterfly species. In her Conservation Biology class, Grames involves undergraduate students in evaluating the conservation status of specific butterflies, such as the Julia’s skipper, one of the species experiencing the sharpest declines. “Participating in this assessment has allowed me to apply what I’ve learned in class to real-world scenarios,” said Clara Zook, a student involved in the assessment. Her classmate, Kieran Buchholz, echoed her sentiments, adding, “It’s empowering to know that our research could play a role in preserving this species.”
The study’s findings have significant policy implications. With better data available than ever before, conservationists and policymakers can make stronger cases for protecting butterfly habitats and species under federal protection programs like the Endangered Species Act or the International Union for Conservation of Nature (IUCN) Red List. “We have much better data to go and say, ‘You know, we should really consider these for federal protection,’” Grames explained. “So we can go in, conserve their habitat and—hopefully—they can rebound.”
Lead author of the study, Collin Edwards, emphasized the broader significance of these findings. “For those who were not already aware of insect declines, this should be a wake-up call,” he warned. “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.”
This research is part of a broader effort to understand insect population declines worldwide. Previous studies have suggested that insects are declining at a rate of about 1–2% per year, and this latest butterfly research aligns with those alarming trends. “This was another study finding a super similar rate of decline, which really adds evidence to the growing picture of insect declines globally,” Grames noted.
While the findings are deeply concerning, they also provide an opportunity for action. Conservation efforts such as creating butterfly-friendly habitats, reducing pesticide use, and mitigating climate change impacts can help slow or reverse declines. Public engagement and policy changes will be critical in protecting these fragile yet essential creatures.
Butterflies are more than just symbols of beauty and transformation—they are integral to our ecosystems and serve as a vital reminder of the interconnectedness of all life forms. Their decline is a warning sign, but with scientific research, conservation efforts, and public awareness, there is still hope for preserving these remarkable insects for future generations.
More information: Collin B. Edwards, Rapid butterfly declines across the United States during the 21st century, Science (2025). DOI: 10.1126/science.adp4671. www.science.org/doi/10.1126/science.adp4671