The Swiss agri-environment scheme enhances pollinator diversity and plant reproductive success in nearby intensively managed farmland.
Abstract
Agri-environment schemes attempt to counteract the loss of biodiversity and associated ecosystem services such as pollination and natural pest control in agro-ecosystems. However, only a few studies have evaluated whether these attempts are successful. We studied the effects of managing meadows according to the prescriptions of ecological compensation areas (ECA), the most widely adopted agri-environment scheme in Switzerland, on both pollinator species richness and abundance, and the reproductive success of plants in nearby intensively managed meadows (IM). We established arrays of four pots, each containing individuals of three insect-pollinated, non-autogamous 'phytometer' species (Raphanus sativus, Hypochaeris radicata and Campanula glomerata), in ECA and adjacent IM at increasing distances from the ECA at 13 sites. Species richness and abundance of hoverflies, solitary bees and large-sized pollinators (mainly social bees and butterflies) were significantly higher in ECA than in adjacent IM. Species richness and abundance of small-sized pollinators in IM declined significantly with increasing distance from ECA, whereas large-sized pollinators were not significantly affected by distance. Plant species richness and flower abundance were the major drivers of pollinator species richness and abundance; the area of an ECA had no significant influence. Individual plants of R. sativus and C. glomerata produced more and heavier seeds in ECA than in IM. Furthermore, the number of seeds of these two phytometer species was positively correlated with species richness and abundance of bees. No such effects were observed for individual plants of H. radicata. The number of fruits and seeds per plant of R. sativus in IM decreased with increasing distance from ECA. Synthesis and applications. We conclude that establishing ECA is an effective method of enhancing both pollinator species richness and abundance and pollination services to nearby intensely managed farmland. Our study emphasizes the importance of connectivity between ECA in maintaining diverse pollinator communities and thereby providing pollination services in agricultural landscapes.