Multi-scale effects of agri-environment schemes on carabid beetles in intensive farmland

Summary

Agri-environment schemes (AESs) were implemented to reduce the loss of biodiversity in agro-ecosystems. This study aimed to assess whether AESs at either local or landscape scale increase the carabid abundance-activity and species richness. Carabids were sampled in 496 fields in a 430 km2 study area of central-western France. Based on the extensiveness of the agricultural practices involved, the different AES types were aggregated into three categories (AESEXT+, AESEXT++ and AESEXT+++) forming a gradient of extensiveness in farming practices. We sampled 20 fields in each of the three AESs categories. Each AES fields was paired with conventional fields. A series of statistical models were built to test the balance between the effects of AESs on either the carabid abundance-activity or species richness. AESs affected carabid abundance-activity and species richness both locally and at landscape scale (local characteristics having a greater effect than landscape composition). Carabid diversity benefited from AESs only when the most extensive practices were implemented, i.e. organic farming in cereal crops and delayed cutting in alfalfa. In addition, the local effects of organic farming and delayed cutting coverage interacted positively with these AESs at landscape scale. These results demonstrate that non-targeted organisms can benefit from AES management. They further emphasize the need to consider both local and landscape conditions when studying the effects of AESs on biodiversity. As only the most extensive practices had significant effects at both local and landscape scales, management must be planned strategically in space to ensure that AESs are distributed within the landscape to amplify their positive effects.