Is greening enough? Short-term limited effects of 2015-2022 European Common Agricultural Policy reform on bird diversity in northern Italy

Agricultural intensification is among the major drivers of biodiversity loss, with cascading effects that compromise the supply of essential ecosystem services. To counteract this process, the European Union integrated voluntary agri-environmental measures into the Common Agricultural Policy (CAP). Since 2015, all CAP direct payments have been tied to the adoption of greening measures (crop diversification, permanent grassland maintenance, ecological focus areas). Using birds as reference taxon, we analyzed whether the implementation of both greening and agri-environmental measures, fostered during the 2015-2022 CAP programming period, enhanced the species richness of overall community, farmland specialists, granivores and insectivores. Applying a cross-sectional approach, we first estimated the overall associations between species richness metrics and sustainable management practices (crop diversification, natural element maintenance, organic, integrated, conservation-tillage farming). Then, employing a longitudinal approach, we evaluated if the implementation of greening practices, promoted by the 2015 CAP reform, increased species richness. All metrics were positively associated with crop diversification. Both overall community richness and insectivorous richness were positively associated with natural elements, while the richness of farmland specialists and granivores showed negative responses. Organic and integrated farming generally promoted species richness, while conservation-tillage farming was negatively associated with insectivorous richness. The longitudinal analysis confirmed that overall community richness benefited from greening interventions promoted by 2015 CAP reform, while farmland specialists, granivorous and insectivorous species richness were not affected in the first years following implementation. We call for evidence-based revisions of CAP agri-environmental measures to improve environmental sustainability of farming without undermining socio-economic sustainability.