From fields to landscapes
Abstract: Farmland biodiversity has declined because of agricultural intensification. Agri-environment schemes (AESs) seem to have limited effect in stopping and reversing declines. Reasons for this lack of effect could be: (1) failure to target important habitats, (2) the effects of schemes are strongly context-dependent, and (3) the effects are measured at the wrong spatial scale. Evidently, we still need more information about the relationships between agricultural land use and biodiversity at local and landscape scale. I investigated how patterns in habitat-specific abundance and species richness of farmland birds related to land use in 37 arable field dominated landscapes (25 km²). The aim of the study was to establish if agricultural land uses, non-crop habitats and AESs are linked to high species diversity or abundance of birds in open plains of southern Sweden. First, I found a clear switch in crop-specific densities (from autumn- to spring-sown) of a farmland specialist species, the skylark (Alauda arvensis), during the breeding season and this temporal change depended on region. Second, I found that farmsteads had higher species richness and abundance of birds compared to semi-natural pastures and infield non-crop islands. The presence of farm animals increased bird diversity and abundance at farmsteads. Furthermore, densities of non-crop nesters at farmsteads increased with increased average field size of the landscape, showing that farmsteads are especially important bird habitats in arable plains. Third, I showed that payments for AESs target important habitats for birds in the region. AESs for cultivated grasslands, semi-natural pastures and management of landscape elements with nature-culture values related positively to species richness or abundance of birds. Landscape level uptake of organic farming did show effects on local species richness depending on the composition of the landscape. Fourth, I showed that heterogeneity of crop cover at the 25 km² scale did not relate to species richness (with the possible exception of field-nesters in the most simplified landscapes). Total species richness of field-nesting species declined in heterogeneous landscapes with more non-crop cover. Farmland plains are important for farmland birds, but variation in species richness there can be found at the beta and gamma levels rather than at the alpha level. My study shows that, biodiversity patterns need to be considered at different spatial scales when designing and evaluating conservation management in farmland.
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