Testing scale-dependent effects of semi-natural habitats on farmland biodiversity

The effectiveness of conservation interventions for maximizing biodiversity benefits from agri-environment schemes (AESs) is expected to depend on the quantity of seminatural habitats in the surrounding landscape. To verify this hypothesis, we developed a hierarchical sampling design to assess the effects of field boundary type and cover of seminatural habitats in the landscape at two nested spatial scales. We sampled three types of field boundaries with increasing structural complexity (grass margin, simple hedgerow, complex hedgerow) in paired landscapes with the presence or absence of seminatural habitats (radius 0.5 km), that in turn, were nested within 15 areas with different proportions of seminatural habitats at a larger spatial scale (10 × 10 km). Overall, 90 field boundaries were sampled across a Mediterranean region (northeastern Italy). We considered species richness response across three different taxonomic groups: vascular plants, butterflies, and tachinid flies. No interac...