A Swiss agri-environment scheme effectively enhances species richness for some taxa over time

The effectiveness of agri-environment schemes (AESs) in promoting biodiversity was recently debated. One reason for limited effectiveness of AESs may be their application to small and scattered patches of land. This study presents the evaluation of a scheme adopted by the canton of Aargau, Switzerland, which seems to be unique in its consequent focus on entire farms, aiming at increasing quality and quantity of ecological compensated areas (ECAs). In vascular plants and snails, the species richness increased during a period of 5 years on plots with AES, but not on control plots without AES. In butterflies and birds, no significant differences were found between AES plots and control plots in the change of species richness over time. While butterfly species numbers generally decreased, bird species numbers increased on both AES plots and control plots. It appears that agri-environment schemes can be effective in protecting and promoting biodiversity, but the effect may depend on the group of organisms.