Data from: 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 interactions between type of field boundary and
surrounding landscape were found at either 0.5 and 10 km, indicating that
the quality of field boundary had the same effect irrespective of the
cover of seminatural habitats. At the local scale, extended-width grass
margins yielded higher plant species richness, while hedgerows yielded
higher species richness of butterflies and tachinids. At the 0.5-km
landscape scale, the effect of the proportion of seminatural habitats was
neutral for plants and tachinids, while butterflies were positively
related to the proportion of forest. At the 10-km landscape scale, only
butterflies responded positively to the proportion of seminatural
habitats. Our study confirmed the importance of testing multiple scales
when considering species from different taxa and with different mobility.
We showed that the quality of field boundaries at the local scale was an
important factor in enhancing farmland biodiversity. For butterflies, AESs
should focus particular attention on preservation of forest patches in
agricultural landscapes within 0.5 km, as well as the conservation of
seminatural habitats at a wider landscape scale.