Preserving habitat quality at local and landscape scales increases wild bee diversity in intensive farming systems

Biological diversity is influenced by many environmental factors, which can act either at a local scale (e.g. quality and quantity of feeding and nesting resources, habitat type) or at a landscape scale (e.g. habitat fragmentation, composition and configuration of landscape features). To effectively manage or promote biodiversity in heterogeneous environments such as intensive agrosystems, a thorough knowledge of the spatial and temporal scale of ecological factor effects is required. This study investigates the effects of ecological correlates on local wild bee diversity in semi-natural farmland habitats, and predicts changes in species richness according to local-scale and landscape-scale correlates to further guide bee conservation practices. Local floral richness, the proportion of semi-natural habitats in the landscape (1000 m radius) and the type of semi-natural habitats influenced bee richness at a field scale. However, the magnitude of the effect varied seasonally and according to local bee abundance. Model predictions showed that increasing floral richness on farms had a greater effect on bee richness than increasing the proportion of semi-natural habitats. While increasing the number of semi-natural habitats would be a more effective strategy for promoting bee diversity at the landscape scale, it may not be feasible in intensive farming systems.