Overlooked jewels: Existing habitat patches complement sown flower strips to conserve pollinators

Flower strips are a frequently adopted measure to conserve insects, especially pollinators, and are subsidized as Agri-Environmental Scheme in many regions. They provide a high quantity of flowers, but their flower species composition and phenological development is mostly uniform. This may result in only a fraction of pollinator species being enhanced. Flower-rich semi-natural habitat patches along slopes, fences or ditches, may provide resources for additional species, but they are not politically promoted. In this study, we compare pollinator communities in sown perennial flower strips with existing flower-rich herbaceous semi-natural habitat patches, both located at the edge of conventional apple orchards in Southern Germany. The flower strips attracted a higher pollinator abundance and species richness than the existing habitat patches. However, the bee species composition differed between the two habitat types. The existing habitat patches attracted bee species with different pollen specialization than the sown flower strips. Pollinator abundance and species richness varied between the different existing habitat patches indicating a high heterogeneity of these existing habitats, whereas the flower strips showed consistently high pollinator abundance and richness. We conclude that existing herbaceous habitat patches are attractive for pollinators and should be promoted by policy actions. Flower-rich semi-natural habitat patches develop without sowing next to typical agricultural landscape elements like slopes, fences and ditches with moderate mowing or herbicide application. They generally do not compete with agricultural land use and thus have a high potential to promote pollinator conservation.