In a comprehensive and sobering new analysis spanning more than three decades of butterfly monitoring across the U.S. Midwest, researchers have uncovered a persistent and widespread decline in butterfly populations. This unprecedented study, led by Michigan State University PhD candidate Wendy Leuenberger and her colleagues, reveals that none of the 136 butterfly species monitored exhibited population growth between 1992 and 2023. This large-scale meta-analysis, integrating over 4.3 million individual observations, offers powerful evidence that both common and rare butterfly species are undergoing serious declines, signaling critical changes in midwestern ecosystems.
The depth and breadth of this research are staggering in scope, derived from tens of thousands of hours of volunteer-driven surveys that have tracked butterfly abundance and species diversity across multiple decades. Volunteers have consistently monitored butterfly populations using standardized protocols, providing invaluable contribution to ecological science. Their efforts have enabled a granular understanding of how butterfly communities have shifted over thirty years, highlighting losses so profound that, on average, every ten species once present in a given county are now reduced to nine, and the total number of individual butterflies has dropped by 40 percent.
Leuenberger’s findings are particularly striking given the scale of data assembled and analyzed. “We expected to see at least some species thriving or maintaining stable populations,” she remarked. The fact that no species showed population increases challenges previous assumptions about resilience in butterfly communities. Many iconic species, including monarchs and cabbage whites, remain broadly present but have suffered steep reductions in numbers. Even rarer species, which are often more vulnerable to environmental shifts, are becoming increasingly elusive.
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The importance of these findings extends beyond butterflies themselves, as these insects serve multiple ecological roles vital to ecosystem function. Butterflies act as key pollinators, facilitating reproduction in a variety of wild plants and agricultural crops. During their larval stage as caterpillars, they are important prey items for young birds, linking them integrally within food webs. Consequently, declines in butterfly populations may undermine not only biodiversity but also broader ecological resilience and agricultural productivity.
This study importantly situates itself within a wider context of insect declines globally, and specifically builds upon recent nationwide assessments. Earlier research published in Science documented decreasing butterfly numbers across the United States from 2000 to 2020, capturing significant losses albeit over a narrower timeframe. By extending the period studied back to 1992, this latest analysis provides crucial historical context linked with key environmental factors.
Although the researchers did not directly analyze causal drivers within this study, temporal overlap suggests potential influences. The onset and increasing application of neonicotinoid insecticides since the mid-1990s coincides with the period of decline. Neonicotinoids have been implicated in other insect population reductions due to their potent neurotoxic effects. Additionally, changing climatic variables driven by global climate change—including altered temperature and precipitation regimes—are likely influencing butterfly distributions and survivorship.
One of the most vital aspects of the research is its attention to the variability in butterfly life histories and traits, which modulate species’ responses to environmental pressures. Butterflies exhibit a range of characteristics: from migratory to sedentary behaviors; from broad generalists to habitat specialists; and from species with multiple annual generations to those with only a single generation per year. These ecological and phenological traits influence resilience, with multi-generational butterflies faring better under changing conditions than single-generation species, as highlighted by Leuenberger.
Understanding this diversity in response patterns is necessary for designing effective conservation strategies that cater to species-specific vulnerabilities. Blanket approaches to conservation may overlook subtle but important differences in habitat needs, seasonal timing, and mobility. The detailed dataset and analyses developed by this team are positioned to inform targeted interventions, policy initiatives, and habitat management programs that can more precisely support biodiversity restoration.
Elise Zipkin, a senior author on the paper and director of the Ecology, Evolution, and Behavior Program at MSU, emphasized the critical role of long-term citizen science contributions to this breakthrough. “Without the sustained, consistent efforts of volunteer scientists using standardized methods over decades, we could not achieve this level of insight,” she noted. This research underscores the power of citizen involvement not only in data collection but also in raising public awareness about biodiversity crises.
Butterflies, often viewed as charismatic insects, have become emblematic of broader environmental challenges affecting insect populations worldwide. Their declines mirror those of many other arthropods, raising alarms about the cascading consequences for ecosystems. This comprehensive temporal and spatial record serves as an urgent call for intensified monitoring, multifaceted research, and conservation policies addressing the complex interplay of factors undermining insect biodiversity.
The social and ecological importance of butterflies and other insects is profound. Beyond ecosystem services such as pollination, they represent living indicators of environmental health. As insect populations decline, there is growing recognition that human well-being is indirectly threatened through compromised ecosystem functions. As Leuenberger cautions, “We depend on insects more than we often realize. Protecting them must become a conservation priority before the declines become irreversible.”
This landmark study, titled “Three decades of declines restructure butterfly communities in the Midwestern United States,” published in the Proceedings of the National Academy of Sciences, advances scientific understanding of insect decline dynamics across a crucial region of North America. Supported by federal agencies including the National Science Foundation and U.S. Geological Survey, it builds a critical foundation for future efforts to halt and reverse the losses of these vital creatures.
Looking ahead, the integration of long-term datasets combined with trait-based ecological insights will enable researchers and conservationists to adaptively manage habitats and mitigate anthropogenic stressors. This study’s expansive temporal view reveals just how rapidly biodiversity can erode, reinforcing the need for proactive interventions grounded in rigorous science and community involvement.
The collapse of butterfly populations in the Midwest signals an ecological crisis as familiar as it is urgently pressing. It represents a profound transformation in natural communities witnessed over the course of just a single generation. As climate change intensifies and chemical exposures persist, understanding and addressing these declines will be imperative for the stewardship of native biodiversity and the sustainability of ecosystems upon which humans depend.
Subject of Research: Animals
Article Title: Three decades of declines restructure butterfly communities in the Midwestern United States
News Publication Date: 1-Aug-2025
Web References: http://dx.doi.org/10.1073/pnas.2501340122
References: Leuenberger et al., Three decades of declines restructure butterfly communities in the Midwestern United States, Proceedings of the National Academy of Sciences, 2025.
Image Credits: Karen Douglas, Kalamazoo Nature Center
Keywords: Butterfly decline, insect population loss, Midwest ecology, biodiversity, citizen science, neonicotinoid insecticides, climate change, pollinators, conservation biology
Tags: big data in environmental sciencebutterfly conservation challengesbutterfly monitoring researchbutterfly species diversity trendscitizen science in ecologyecosystem changes in the Midwestimpact of climate change on butterflieslong-term ecological studiesMichigan State University researchMidwestern butterfly population declineshifts in butterfly communitiesvolunteer-driven ecological surveys