Indirect effects of grassland extensification schemes on pollinators in two contrasting European countries

Flower-visiting insects play a crucial role in ecosystem processes by providing essential services such as pollination. During the last decades, agricultural intensification has caused a widespread decline of insect diversity. Agri-environment schemes (AES) have been implemented in many European countries to counteract the loss of biodiversity. Here, we present results of a study evaluating effects of AES on pollinators and the insect-pollinated plants in grasslands of two contrasting European countries: Switzerland and The Netherlands. We compare species composition and abundance of bees and insect-pollinated plants in 37 field pairs, one with an AES, the other conventionally managed. AES significantly affected species-richness and abundance of non-Apis bees in Switzerland. Schemes did not have an effect in The Netherlands where bee species number and abundance was much lower than in Switzerland. The different effectiveness between countries can be explained by different contextual conditions and different effects of AES management prescriptions on the food resource of wild bees. We conclude that in order to stop the overall loss of agro-biodiversity, it can be recommended to include additional measures which focus specifically on the enhancement of bees or other arthropods.