Toward the next Common Agricultural Policy reform:Determinants of avian communities in hay meadows reveal current policy's inadequacy for biodiversity conservation in grassland ecosystems

摘要

1.Semi-natural grasslands are among the richest European ecosystems in terms of biodiversity.However,they have been severely affected by farming intensification and land abandonment,which have been both exacerbated by the European Union's Common Agricultural Policy (CAP).The most recent CAP included a “greening” measure dedicated to grassland conservation,presumed to be beneficial to biodiversity;however,scientific evidence about its effectiveness is still scarce.2.In the Alps,hay meadows have undergone dramatic management changes in recent decades.We used a comprehensive community ecology approach to highlight how the multi-scale and interacting effects of such changes impact birds,with the aim of providing knowledge to support improvements to the CAP.3.Birds were surveyed at 63 landscape units in northeast Italy,equally subdivided into areas dominated by (a) extensive hay meadows,(b) intensive hay meadows,and (c) areas formerly dominated by meadows but partially converted into other agricultural land use.This environmental gradient mirrors in space the temporal gradient of the agricultural changes that have recently occurred in the Alps.4.Community composition,species richness,and the number of meadow-specialist species were analysed according to environmental predictors (i.e.landscape,meadow management,and topography),and to spatial factors.We aimed to disentangle the exclusive and joint fraction of variation explained by each of them.5.Meadow conversion,allowed by the CAP in force,created a shift in community composition towards assemblages dominated by generalist species at the expense of meadow specialists.The cover of intensive meadows was negatively correlated with species richness,whereas the number of meadow specialists was negatively correlated with the cover of early-mown (i.e.within the third week of June) meadows.Mowing date was,in turn,related to elevation,with meadows at higher elevations mown later in the season,and to meadow intensification (the