The extension of intensive monocultures is the main cause of the decline in bird populations that Europe has suffered in the last 40 years, as confirmed by a scientific study published in the journal PNAS by an international team of fifty researchers, led by scientists from the University of Montpellier, with the participation in Catalonia and the rest of Spain of experts from Creaf, ICO and CSIC.
The authors calculate that bird populations have been reduced by 25% on average, but the decline is close to 60% in the case of species typical of agricultural land. In each country they have decreased in a different way according to the characteristics of their agricultural practices. For example, the regions of Western Europe, where the plots of crops are usually large and the use of pesticides intense, are among the most affected, compared to the countries of the East, where these practices are not so marked.
Another particular case is the Mediterranean basin, where the characteristic relief of the terrain has made it possible to maintain, at least in certain areas, a mosaic agricultural landscape, with vegetal and stone margins and crops combined with natural habitats, "this has helped to cushion the loss of birds”, explains Sergi Herrando, a researcher at Creaf, the Catalan Institute of Ornithology (ICO) and the European Bird Census Council and one of the co-authors of the article.
According to the study, with the intensification of agriculture, the use of fertilizers and pesticides has increased, products that eliminate insects and other invertebrates from the soil, essential food for many birds, "especially during the breeding season when the chicks need a lot of protein", comments Lluís Brotons, a CSIC researcher at Creaf and another of the co-authors. These products also contaminate the seeds and, if the birds ingest them, the toxic substances accumulate in their bodies and can even cause their death.
On the other hand, monocultures generate homogeneous landscapes, where the diversity of vegetation is eliminated, so that birds cannot feed on varied plants and fruits or seek refuge. The authors warn that this not only affects the typical species of cultivation areas such as the Lark or the Yellowhammer, but also other species that go to the crops to feed. Among them, those that have a diet based on invertebrates, such as the common swallow or long-distance migrants, such as the turtle dove, "in short, the majority of common birds," Brotons points out.
The study has analyzed 170 common bird species, which have been observed in more than 20,000 locations in 28 European countries over 37 years. According to Stanislas Rigal, a researcher at the University of Montpellier and lead author of the study, "the results leave no room for doubt, it is not a local problem, the detrimental effects of large crops, fertilizers and pesticides spread throughout Europe. We need to speed up regulation of agricultural practices and implement more sustainable models”.
The research has also analyzed the weight that climate change, urbanization and changes in the forest landscape have on the decline of species. The results point to climate change as the second cause of the decrease, behind agricultural intensification, since the increase in temperature has led to a loss of 40% of bird populations typical of cold environments and 18% of In warm habitats, "this difference is probably due to the fact that the characteristic birds of high latitudes and altitudes are less adapted to heat," explains Herrando.
Urbanization is positioned as the third factor, "there are fewer and fewer green areas and more buildings in cities" and bird populations in urban areas have decreased by 28%. Finally, typical forest birds have decreased by approximately 18%, a figure that contrasts with the increase in forest cover in Europe in recent years. According to the authors, this is explained because the new forests have less quality, that is, they have lost centenary trees and the fauna and flora have been simplified.
“The four human pressures that we describe in the article have already caused together a decline of 25% of the total number of birds in Europe. The descent continues. To stop it, we need transformative changes in European societies. New political pacts such as the European Restoration Law that is being negotiated in the European Parliament can help promote them”, concludes Brotons.
Reference article: Stanislas Rigal et al. Farmland practices are driving bird population decline across Europe. PNAS,
