Effect of conservation management on bees and insect-pollinated grassland plant communities in three European countries

It is now widely accepted that agricultural intensification drives the decline of biodiversity and related ecosystem services like pollination. Conservation management, such as agri-environment schemes (AES), has been introduced to counteract these declines, but in Western European countries these tend to produce mixed biodiversity benefits. Not much is known about the effects of AES in Central and Eastern European countries. We evaluated the effect of reduced stocking rates (0.5cow/ha vs. >1cow/ha) on bees and insect-pollinated plants in semi-natural pastures in Hungary. We sampled bees using sweep net and transect surveys in the edge and interior of the fields three times in 2003. On the same transects, we also estimated the cover of all plant species. We found no management effect on species richness and abundance with respect to cover of bees and insect-pollinated plants, but grazing intensity resulted in differences in species composition of insect-pollinated plants. Furthermore, we compared our results with those of a similar study carried out in Switzerland, and the Netherlands, but with different management regimes. There were positive effects of management in Switzerland, but conservation effects were lacking in the Netherlands. Species richness of both bees and insect-pollinated plants was highest in Hungary, intermediate in Switzerland and lowest in the Netherlands. Across all countries, the richness of insect-pollinated plants was a good predictor of bee species richness. Grassland extensification schemes were effective for bees and insect-pollinated plants in the country with intermediate land-use intensity and biodiversity only (Switzerland). The absence of effects in the Netherlands may have been caused by the management being highly intensive on both field types. In Hungarian grasslands biodiversity levels were high regardless of management and both investigated stocking rates may be qualified as conservation management. Therefore, agricultural policy in Hungary should encourage the maintenance of a variety of traditional grazing practices for conserving this still highly diverse pollinator fauna.