Trends in abundance and biomass of widespread European farmland birds : how much have we lost ?

Analysis of an extensive European dataset confirms the large decline of widespread farmland birds across Europe. Common farmland birds have on average fallen in number by nearly half – the most severe decline of the bird groups considered. Among the 36 species that were classified as characteristic of farmland, 20 have declined, seven have increased, four have remained stable and trends of five were classified as uncertain. In parallel with the index of abundance, we show for the first time that an overall index of biomass of farmland birds in Europe has more than halved during the last 27 years. Differences between trends of farmland birds in four European regions are not significant, but trends in New EU Member States have been less negative than those in Old EU Member States. Long-distance migrants among the farmland birds have less negative trends than those that are short-distance migrants or residents in Europe. A wide range of studies suggest that changes in land and crop management have been the main cause of farmland bird declines, although population declines in arable landscapes of south and central-eastern Europe may be linked to land abandonment and afforestation. In contrast, populations of all common species taken together, or common forest species from within that group, have declined modestly over the last 27 years. Similarly, overall biomass of these two groups has declined slightly, although biomass of both has inceased over the last 5 years. The pattern of changes in bird abundance and biomass detected in European farmland birds suggests a considerable loss of European biodiversity and a likely loss of ecosystem function and services.