Intensive farming is causing birds to disappear in Europe
A large-scale European scientific collaboration has quantified for the first time the direct impact of various human activities on birds across the continent: data collected over nearly 40 years show a loss of almost a quarter of the bird population over this period. More specifically, the study demonstrates the negative and predominant effect of intensified agricultural practices. This work, led by two scientists from the CNRS and a doctoral student from the University of Montpellier, involved researchers from the National Museum of Natural History and many European countries. It will be published in PNAS during the week of May 15, 2023.
Around 20 million. That is the average number of birds disappearing in Europe every year for the past 40 years. That's 800 million fewer birds since 1980. These figures have just been established by a European team which, in a single study, has demonstrated that changes in agricultural practices are the main cause.
To do this, scientists compared several pressures linked to human activity: changes in temperature, urbanization, forest areas, and agricultural practices. This enabled them to quantify and rank their impact on bird populations for the first time, compiling the most comprehensive dataset ever assembled: 37 years of data from 20,000 ecological monitoring sites in 28 European countries, covering 170 different bird species. This data even allows for detailed observation of the cumulative effects of pressures at the level of each country, from one year to the next.
While bird populations suffer from this "cocktail" of pressures, research shows that the dominant harmful effect is that of agricultural intensification, i.e., the increase in the amount of fertilizer and pesticides used per hectare. This has led to the decline of many bird populations, especially insectivorous birds. Fertilizers and pesticides can disrupt the balance of an ecosystem's entire food chain.
The other major pressure is related to the overall rise in temperatures, which of course affects cold-preferring species more severely, with a 40% decline, but also affects warm-preferring species, with an 18% decline. Finally, while bird numbers have fallen across the continent, some ecosystems are more severely affected than others: while forest bird numbers have declined by 18%, this figure rises to 28% for urban birds and jumps to 57% for birds in agricultural environments.
France is a good reflection of the situation in Europe: it is one of the countries with the highest amount of intensively farmed land, but also one of those where this area has increased the most recently. The temperature has also risen by around 1°C between 1996 and 2016, the area of artificial 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 has increased by 9%. Some species have seen their populations decline dramatically: by around 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 requirements. 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 a resource for other predatory species. Their disappearance thus jeopardizes entire ecosystems.
This research demonstrates the urgent need to rethink current food production methods. It was supported by the French Office for Biodiversity and involved scientists 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) in France.
- The number of birds has declined by 25% in 40 years on the European continent, and by nearly 60% for species in agricultural environments.
- Intensive agriculture is the main pressure associated with the decline in bird populations.
- These results come from the largest and most comprehensive study to date on birds in Europe.
Bibliography
Farmland practices are driving bird populations decline across Europe. Rigal , S et al. PNAS, week of May 15, 2023.