The intensification of agriculture is causing the decline of bird populations in Europe
A large-scale European scientific collaboration has, for the first time, quantified the direct impact of various human activities on birds across the continent: data collected over nearly 40 years show a decline of nearly a quarter in bird populations during that period. More specifically, the study demonstrates the significant negative impact of intensified agricultural practices. This research, led by two CNRS scientists and a doctoral student from the University of Montpellier, involved researchers from the National Museum of Natural History and numerous European countries. It was published in PNAS the week of May 15, 2023.
About 20 million. That is the average number of birds disappearing in Europe each year over the past nearly 40 years. That amounts to 800 million fewer birds since 1980. These figures were recently calculated by a European team that demonstrated, in a single study, that changes in agricultural practices are the primary cause.
To do this, the scientists compared several human-induced pressures: changes in temperature, urbanization, forest cover, and agricultural practices. They were thus able to quantify and rank these factors’ impacts on bird populations for the first time, by compiling the most comprehensive dataset ever assembled: 37 years of data from 20,000 ecological monitoring sites across 28 European countries, covering 170 different bird species. These data even allow for a detailed observation of the cumulative effects of these pressures at the national level, year over year.
While bird populations are suffering from this “cocktail” of pressures, research shows that the dominant harmful effect is that of agricultural intensification—that is, the increase in the amount of fertilizer and pesticides used per hectare. This has led to the decline of many bird populations, particularly insectivorous birds. Indeed, fertilizers and pesticides can disrupt the balance of an ecosystem’s entire food chain.
The other major pressure is that associated with rising global temperatures, which naturally affects cold-loving species more severely—with a 40% decline—but does not spare warm-loving species, which have also seen an 18% decline. Finally, while bird numbers have fallen across the continent, some ecosystems are harder hit than others: while forest bird populations have declined by 18%, this figure rises to 28% for urban birds and jumps to 57% for birds in agricultural areas.
France is a good reflection of the situation across Europe: it ranks among the countries with the largest area of intensively farmed land, but also among those where this area has increased the most in recent years. Temperatures also rose by about 1°C between 1996 and 2016; the area of urbanized land is above the European average, and forest cover is below the European average, even though it has increased since 1996. The number of farmland and forest birds has declined by 43% and 19%, respectively. The number of birds nesting in urban areas, however, has increased by 9%. Some species have seen their populations plummet dramatically: by approximately 75% for the tree sparrow, the whinchat, and the meadow pipit, for example.
This decline illustrates the impact of human activities on an entire group of species with very different needs. It is a sign of profound environmental degradation. More directly, birds are involved in fundamental interactions within ecosystems: predation and regulation of other species, seed dispersal, and serving as food for other predatory species. Their disappearance thus threatens entire ecosystems.
This research highlights the urgent need to rethink current food production methods. It was supported by the French Office for Biodiversity and involved scientists in France from the Institute of Evolutionary Sciences in Montpellier (CNRS/IRD/University of Montpellier) and the Center for Ecology and Conservation Sciences (CNRS/MNHN/Sorbonne University).
- The number of birds has declined by 25% over the past 40 years across Europe, and by nearly 60% for species found in agricultural areas.
- Intensive agriculture is the main factor contributing to the decline in bird populations.
- These findings come from the largest and most comprehensive study to date on birds in Europe.
Bibliography
. Farmland practices are driving the decline of bird populations across Europe. Rigal , S. et al. PNAS, week of May 15, 2023.