Accelerated farmland bird population declines in European countries after their recent EU accession.

Agricultural intensification is a major driver of global biodiversity loss. In Europe, intensification progressed over the 20th century and was accelerated by instruments of the EU's Common Agricultural Policy. Central and Eastern European (CEE) countries standing outside the EU until the beginning of the 21st century employed less intensive farming and are considered one of the continent's farmland biodiversity strongholds. Their recent EU accession might be either viewed as a threat to farmland biodiversity due to the availability of funds to increase agricultural production or as an opportunity to implement conservation measures aimed to preserve biodiversity. Here we assessed these possibilities using long-term monitoring data on farmland bird populations in seven CEE countries. We tested whether mean relative abundance and population trends changed after countries' EU accession, and whether such changes also occurred in agricultural management and conservation measures. Both agricultural intensity and spending for agri-environmental and climatic schemes increased when the CEE countries joined the EU. At the same time, farmland bird populations started to decline and their relative abundance was lower after than before EU accession. In addition, increases in fertilizer application were negatively associated with annual changes in relative farmland bird population sizes, indicating a negative impact of intensive agriculture. Taken together, these results indicate that despite the great power of the EU's environmental legislation to improve the population status of species at risk, this does not apply to farmland birds. In their case, the adverse impacts of agricultural intensification most likely overrode the possible benefits of conservation measures. To secure this region as one of the continent's farmland biodiversity strongholds, policy and management actions are urgently needed.

Farmland practices are driving bird population decline across Europe.

Declines in European bird populations are reported for decades but the direct effect of major anthropogenic pressures on such declines remains unquantified. Causal relationships between pressures and bird population responses are difficult to identify as pressures interact at different spatial scales and responses vary among species. Here, we uncover direct relationships between population time-series of 170 common bird species, monitored at more than 20,000 sites in 28 European countries, over 37 y, and four widespread anthropogenic pressures: agricultural intensification, change in forest cover, urbanisation and temperature change over the last decades. We quantify the influence of each pressure on population time-series and its importance relative to other pressures, and we identify traits of most affected species. We find that agricultural intensification, in particular pesticides and fertiliser use, is the main pressure for most bird population declines, especially for invertebrate feeders. Responses to changes in forest cover, urbanisation and temperature are more species-specific. Specifically, forest cover is associated with a positive effect and growing urbanisation with a negative effect on population dynamics, while temperature change has an effect on the dynamics of a large number of bird populations, the magnitude and direction of which depend on species' thermal preferences. Our results not only confirm the pervasive and strong effects of anthropogenic pressures on common breeding birds, but quantify the relative strength of these effects stressing the urgent need for transformative changes in the way of inhabiting the world in European countries, if bird populations shall have a chance of recovering.

Long-term and large-scale multispecies dataset tracking population changes of common European breeding birds.

Around fifteen thousand fieldworkers annually count breeding birds using standardized protocols in 28 European countries. The observations are collected by using country-specific and standardized protocols, validated, summarized and finally used for the production of continent-wide annual and long-term indices of population size changes of 170 species. Here, we present the database and provide a detailed summary of the methodology used for fieldwork and calculation of the relative population size change estimates. We also provide a brief overview of how the data are used in research, conservation and policy. We believe this unique database, based on decades of bird monitoring alongside the comprehensive summary of its methodology, will facilitate and encourage further use of the Pan-European Common Bird Monitoring Scheme results.