Intensification of agriculture has been detrimental for the biodiversity of agricultural habitats. Especially the loss of traditionally managed meadows but also the common replacement of open ditches by subsurface drainage and has had large negative impacts on biodiversity in North-European agricultural ecosystems. Field unit amalgamation has further decreased the amount of field boundary habitats. We investigated how habitat type and landscape structure affect alpha- and beta-diversity of butterflies. We were particularly interested in examining the joint effect of landscape structure and field boundaries on lepidopteran diversity. Butterflies were censused in field margins, forest edges and patches of semi-natural grassland in 68 agricultural landscapes.
Results/Conclusions
Habitat type had clear effects on butterfly alpha- and beta-diversity, small meadow fragments being superior to forest edges and field margins. Components of butterfly diversity were significantly explained by land-use intensity and habitat diversity at two spatial scales. The relative significance of field boundaries for the regional species pool increased with increasing intensity of agricultural land use and with decreasing landscape heterogeneity. Our results demonstrate (i) that even small patches of semi-natural meadow can act as species richness hot-spots in ordinary agricultural landscapes and (ii) that the relative importance of field boundaries on butterfly diversity is dependent on landscape context. The latter finding is analogical with results demonstrating an increasing importance of organic farming with decreasing landscape heterogeneity in European agricultural landscapes. Our results also suggest that selection on the loss of specialists is greater than selection against migration. Our results suggest that agri-environment schemes should direct efforts to preserve and widen remaining field boundaries especially in intensively cultivated agricultural landscapes.
