Significance
Using the most recent and largest empirical dataset ever assembled for Europe to investigate the effect of anthropogenic pressures, we highlighted the predominant detrimental impact of agriculture intensification on avian biodiversity at a continental scale over climate change, urbanization, and forest cover changes. Our results do not simply quantify correlations, but our analytical design is meant to strive for more quasicausal responses of bird populations to global change drivers. This paper contributes to the highest political and technical challenge faced by agricultural policy in Europe, struggling to balance high productivity from intensive agricultural practices with environmental protection, and the results are therefore crucial to policymakers, scientists, and the general public concerned for biodiversity and global change issues.
Abstract
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.
Temporal change in bird abundance in Europe between 1996 and 2016 for countries participating in the PanEuropean Common Bird Monitoring Scheme (PECBMS) (n = 28, non-PECBMS countries in gray). For each country, the color represents the slope (red for decline, blue for increase) and the black line corresponds to the time series of the multispecies index (MSI) between 1996 and 2016 (species lists by country in SI Appendix, Appendix 5). (A) Change in abundance of farmland species (MSI by country on 19 species) showing an overall sharp while decelerating decline. (B) Change in abundance of woodland species (MSI by country on 25 species) showing an overall linear decline. (C) Change in abundance of urban dwellers (MSI by country on 22 species) showing an overall stable trajectory. (D) Change in abundance of cold dwellers (light gray, MSI by country on 35 species) showing an overall linear decline. Change in abundance of hot dwellers (dark gray, MSI by country on 35 species) showing an overall stable trajectory. Color for hot dweller trends on the southern part of countries and color for cold dwellers on the northern part of countries.
Anthropogenic pressures for countries participating in the PanEuropean Common Bird Monitoring Scheme (PECBMS) (n = 28, non-PECBMS countries and countries with no available data in gray). For each country and each pressure, the color represents the mean and the black line corresponds to the time series. (A) High-input farm cover (% of total cultivated area covered by high-input farms), period covered by data 2007 to 2016. (B) Forest cover (% of the country’s surface), 1996 to 2016. (C) Urbanization (% of the country’s surface), 2009 to 2016. (D) Temperature (°C), 1996 to 2016.
Relationship between anthropogenic pressures and bird trends and time series. (A) Relative effects of high-input farm cover, forest cover, urbanization, and temperature and their trends on bird trends (1996 to 2016, 141 species) obtained by partial least square regression (PLS). Bias-corrected and accelerated CIs are displayed. (B) Distribution of the strength of the influence of pressures (scaled S-map coefficients) on bird time series. The number of species with negative and positive mean S-map coefficients is shown.
Results of the partial least square regression between each pressure influence on species time series and species traits. Nonsignificant effects are shown in gray, negative effects are shown in light red, and positive effects are shown in blue. The magnitude of the effect is displayed by the line width, scaled for each pressure.
