The area has seen a continued rise in intensive monoculture, a practice largely blamed for the decline in bird populations across Europe over the past four decades. On average, bird numbers have fallen by about 25%, while native farmland species have suffered reductions of nearly 60%.
New findings published in the Proceedings of the National Academy of Sciences (PNAS) show that national declines vary with farming practices. Western European regions, where large crop fields and heavy pesticide use prevail, show some of the steepest declines. In contrast, eastern countries with less consolidated farming methods show relatively milder losses.
In the Mediterranean basin, the terrain supports a mosaic agricultural landscape that blends vegetable and stone margins with crops alongside natural habitats. This pattern appears to help lessen bird losses. “The varied landscape helps maintain habitats for different species,” notes Sergi Herrando, a researcher with CREAF, the Catalan Institute of Ornithology, and a contributor to the European Bird Census Council.
According to the study, intensified agriculture brings greater use of fertilizers and pesticides, substances that kill insects and other invertebrates that many birds rely on for food, especially during breeding when chicks require high protein intake. Lluís Brotons, a CSIC researcher and CREAF co-author, emphasizes that these products also contaminate seeds, and if birds ingest them, toxic substances can accumulate and even cause death.
These factors contribute to a broader decline: monocultures create uniform landscapes with reduced plant diversity, leaving birds with fewer feeding options and shelter. The researchers warn that this issue affects more than just traditional ground-foraging species; it also threatens other birds that depend on crops for food. Among those most affected are insect-eating birds and long-distance migrants, such as swallows and doves, which rely heavily on invertebrates found in agricultural areas.
Photos accompanying the study illustrate the impact: pesticides can destroy insect food sources crucial for insectivorous birds.
The research followed 170 common bird species across more than 20,000 locations in 28 European countries over 37 years. Lead author Stanislas Rigal, from the University of Montpellier, states that the findings indicate a continent-wide problem. The scale of impact from large crops, fertilizers, and pesticides calls for rapid changes in agricultural practices and a shift toward more sustainable models [Source: PNAS].
Climate change emerges as a secondary driver of the declines. The analysis indicates that warming temperatures and urban expansion contribute to shifts in habitat suitability. In recent years, heat stress has led to the loss of about 40% of cold-adapted bird populations and 18% of species in warmer habitats. Herrando explains that birds native to higher latitudes and elevations struggle more with heat stress.
Urban expansion ranks as the third factor: cities host less green space and more built environments, contributing to a 28% decrease in urban bird populations. Forest-dwelling birds also show declines, about 18%, due to the degradation of forest quality and the loss of centuries-old trees and associated flora and fauna.
The authors summarize the four human pressures as a cumulative 25% reduction in Europe’s bird populations, with the trend continuing. They argue that only transformative shifts in European policy and practice can reverse this course. Initiatives under consideration in the European Parliament, including proposals for broader restoration targets, could help drive these changes, according to Brotons.
Note: This summary reflects the study’s findings and the authors’ recommendations for policy and practice reform [Source: PNAS].
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