In Europe, bird populations have declined on average by 25% in the last 40 years, a figure that rises to 60% in the case of species linked to agricultural land. Intensive food production is mainly responsible for such a loss of biodiversity, due to monocultures and the massive use of pesticides and fertilizers that eliminate insects and plants, the basis of food and shelter for birds, says a comprehensive study published Monday in the scientific journal PNAS. But it is not the only obstacle to overcome by birds. Climate change comes in second and is behind the loss of 40%, on average, of birds in cold environments and 18% of those living in warm places. Urbanization, the third factor analyzed, has eliminated 28% of birds from urban environments. The researchers have reached these conclusions after breaking down data collected over 37 years (from 1980 to 2016) concerning 178 common bird species, observed in 20,000 different places in 28 European countries.
"The important thing is that, for the first time, we have joined all the pieces that we knew separately and we have quantified the affections, to find out in which places the birds are worse or better," explains Sergi Herrando, researcher at the Center for Ecological Research and Forest Applications (CREAF) of the Autonomous University of Barcelona and the Catalan Institute of Ornithology (ICO) and co-author of the study. The study has linked the state of birds in agricultural, urban, forest and hot and cold environments, with the conditions they suffer from human activities and climate change.
European roller, one of the species affected by intensive agriculture. Xavier Riera
To do this, the authors have examined the information collected annually by the network of volunteers coordinated in each country, which is integrated into the Pan-European Monitoring Program for Common Birds (PECBMS), whose objective is to use these animals as indicators of the general state of nature, because they are very sensitive to environmental changes and easy to observe.
Researchers have found that in each country the birds have declined differently, depending on their agricultural practices. Regions of Western Europe, where crop plots are often large and with significant pesticide use, are among the most affected. However, in the countries of the East the situation is better. "It also has to do with the economic situation of nations, a hectare of irrigated land in Holland, a country with high purchasing power, is not the same as in Romania, where resources are scarce and they do not have the capacity to acquire so many inputs," says Herrando as an example.
A global problem
Despite these peculiarities by country, the problem is "global", warns Stanislas Rigal, researcher at the University of Montpellier and lead author of the research. "The detrimental effects of large crops, fertilizers and pesticides are spreading throughout Europe," he said in a press release. The solution lies in producing food more sustainably and continuing research, because the existing information in Europe on the chemicals used is not complete. "The decline continues [of birds]," warns Lluís Brotons, CSIC researcher and co-author of the study. To stop it, "transformative changes are needed in European societies, which can be encouraged with new political pacts such as the European Restoration Law that is being negotiated"
The harmful impact of these substances on insects and other invertebrates further complicates the situation, the study maintains. They are "crucial" species during the breeding period of 143 of the 173 types of birds analyzed, so it could affect their reproductive success by modifying the behavior of parents and the survival of chickens, which need protein. In addition, the effect that can produce feeding with seeds that are contaminated and "toxic substances accumulate in their body and can cause death," says Lluís Brotons, CSIC researcher and also co-author of the study.
Birds not only disappear in agricultural territory, the typical species of forests (woodpeckers, titches, robins, chickadees ...) have decreased an average of 18%. This finding contrasts with the increase in forest cover in Europe – 9% in the last 30 years, according to a report by Forest Europe. If there are more trees, more vegetation, what is happening? "The forests have less quality, they have lost centenary trees and the fauna and flora has been simplified" by the management or the fires, responds the study. Herrando adds that there are forests in the Scandinavian countries (Norway, Finland ...) that are managed as farms similar to conventional farms, as if it were "harvesting lettuce". "Many trees are planted, but nothing more than that and birds and other species have nowhere to take refuge [as happens in monocultures] and they are declining," he explains. A scenario that, however, changes in southern Europe, where the typical birds of the forests have increased.
The Mediterranean basin is another particular case. The relief, more mountainous and abrupt than in areas of central Europe or the Atlantic area, has allowed to maintain, "at least in certain parts", a traditional agricultural landscape, in mosaic, with traditional and family agriculture that slows the descent of birds, which occurs in large cultivated areas, open and continuous.
"Spain is very diverse, it has intensive agriculture areas in Murcia, Andalusia, in the Ebro valley... But, having greater landscape diversity, the affection to birds is less than in Holland or Germany, "explains Herrando. The conservation policy, in his opinion, has been quite good, especially for emblematic species such as the imperial eagle, the vulture ..., "but we have forgotten the smaller ones, which maintain the ecological network, dispersing the seeds or with the control of insects. So we are not going to save the little bustard, "he points out in reference to a steppe bird declared this year in danger of extinction.
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