In a groundbreaking study published in Science on February 26, 2026, researchers reveal a troubling acceleration in the decline of bird populations across North America, intensifying since the mid-1980s. While the overarching phenomenon of bird population losses has long been recognized, this study is the first to pinpoint specific regional hotspots where the rate of decline has surged markedly. The implications of these findings extend far beyond avian ecology, implicating broader environmental health and ecosystem services vital to humanity.
The research utilized data from the North American Breeding Bird Survey, an extensive annual multinational monitoring program, analyzing data from 1,033 survey routes covering the years 1987 through 2021. This robust dataset encompasses observations of 261 bird species, spanning 54 avian families and 10 diverse habitat types. The comprehensive approach allowed for detailed modeling of both abundance change and the rate of change—encompassing acceleration and deceleration patterns—allowing the investigators to move beyond mere average declines and elucidate dynamic trends over time.
What emerged was unequivocal: a continent-wide reduction in overall bird abundance, with nearly half of the surveyed species, 122 in total, experiencing significant population decreases. More alarmingly, 63 of these species demonstrated an accelerating downward trajectory. Notably, the researchers identified three geographic regions where this acceleration clustered intensively—the Midwest, California, and the Mid-Atlantic states. Only a narrow area just north of the U.S.-Canadian border exhibited an increase in total bird abundance, highlighting the paucity of positive trends amidst widespread losses.
The analytical focus then shifted to dissecting potential drivers underlying this spatial heterogeneity in decline rates. By integrating environmental variables and human activity metrics—such as mean temperature shifts, precipitation patterns, land cover changes, cropland extent, fertilizer and pesticide application rates, vegetation dynamics, and the human footprint index—the search for explanatory factors became multidimensional. Statistical modeling unequivocally demonstrated that agricultural intensity stood out as the primary predictor for these accelerated decline hotspots.
Agricultural intensity was quantified through a combination of cropland coverage and the magnitude of fertilizer and pesticide use, reflecting modern industrial agricultural practices. Although the correlative nature of the analysis precludes pinpointing which specific agricultural factors are most culpable, the overarching message is clear: regions with intensive farming practices experience disproportionate and accelerating losses of bird abundance. This relationship likely emerges from habitat conversion, chemical exposure, and resource depletion characteristic of high-intensity agriculture, exerting multifaceted pressures on avian populations.
Beyond affecting species traditionally categorized as farmland birds, the decline resonates across taxonomic groups and functional traits. Twice as many species manifested accelerating declines compared to mitigations or slowing in decline, a pattern discernible even at the family taxonomic level. This broad taxonomic footprint underscores systemic ecological disruptions, as diverse bird species from varying ecological niches succumb to the mounting pressures of altered landscapes and chemical inputs.
Understanding bird population dynamics is critical not only for conservation biology but also because birds perform indispensable ecosystem services. They regulate insect populations, curbing pest outbreaks that can jeopardize agricultural productivity and forest health. Additionally, many bird species act as seed dispersers, fostering plant genetic diversity and resilience by distributing seeds across various spatial scales. The decline in bird abundance thus reverberates through trophic networks, imperiling ecosystem function and stability at multiple levels.
The researchers estimated an average 15% loss in bird abundance per survey route over the 35-year span, a conservative yet statistically robust indication of widespread population declines. By focusing on local scales, the study avoided the pitfalls of extrapolation, providing a more reliable assessment of changes that aligns with ecological realities on the ground. Such data provide a sobering indictment of the impacts stemming from anthropogenic environmental transformation.
Lead author François Leroy from The Ohio State University situates these findings within the broader context of the Anthropocene, an epoch characterized by accelerating human impacts on global ecosystems since the mid-20th century. Human land use changes, including expansive agricultural development and intensification, have reshaped habitats and altered ecological interactions. The study’s results align with a growing body of evidence that human activities remain the dominant force influencing biodiversity trajectories globally.
Despite the grim outlook, Leroy maintains a cautious optimism grounded in ecological resilience. Biodiversity is dynamic, and recovery is possible if environmental pressures are mitigated and habitats restored. Proactive conservation efforts, policy innovation targeting sustainable agriculture, and landscape management encouraging habitat heterogeneity can reverse declines. The window for effective intervention still exists, and decisive action can yield measurable improvement in avian population trends within decades.
The collaborative project also involved Marta Jarzyna of Ohio State University and Petr Keil of the Czech University of Life Sciences, supported by funding mechanisms including the European Union, the U.S. National Science Foundation, and the Czech Science Foundation. Their interdisciplinary approach, integrating long-term monitoring data with environmental and anthropogenic variables, sets a benchmark for future biodiversity research amid rapid environmental change.
In sum, this study marks a critical advance in understanding not only the magnitude of bird population declines but also the spatial and temporal nuances driving these trends. By spotlighting agricultural intensification as a key factor accelerating bird declines across multiple taxonomic groups and regions, it underscores the urgent need for sustainable land use practices that reconcile food production with biodiversity conservation in North America and beyond.
Subject of Research:
Bird population decline and its association with agricultural intensity in North America
Article Title:
Acceleration hotspots of North American birds’ decline are associated with agriculture
News Publication Date:
26-Feb-2026
Web References:
- North American Breeding Bird Survey: https://www.usgs.gov/centers/eesc/science/north-american-breeding-bird-survey
- Human Footprint Index: https://wcshumanfootprint.org/
- Study DOI: http://dx.doi.org/10.1126/science.ads0871
References:
Leroy, F., Jarzyna, M., Keil, P. (2026). Acceleration hotspots of North American birds’ decline are associated with agriculture. Science. DOI: 10.1126/science.ads0871
Keywords:
Bird population decline, North America, agriculture intensity, avian biodiversity, ecosystem services, pesticide use, fertilizer impact, habitat loss, anthropogenic effects, accelerated decline, breeding bird survey
