Urbanization versus other land use: Diverging effects on dragonfly communities in Germany

Aim Land use change, such as urbanization and intensification of agricultural practices, poses major threats for biodiversity. We examined whether the composition of freshwater species differs between landscapes dominated by urban, agricultural or more natural structures in a region with a long history of landscape transformation. We determined the differences and characteristics of the dragonfly fauna in relation to major land use categories. We particularly focused on urban land use, as it generally induces a high level of landscape transformation. Location Germany. Methods We used distribution data of dragonflies derived from a citizen science database, which was compiled for the German distribution atlas. To analyse whether different land use categories are associated with distinct species compositions, we performed the classification method random forest. Results Based on dragonfly abundance per grid cell, we identified distinct land use-related assemblages that were separated by two gradients, that is, the level of transformation and a gradient from open land to forest. In particular, urban landscapes possessed a distinct species composition with specific species, all of which were opportunistic and supported by warm climate. They also comprised significantly higher alpha-diversity than intensive agricultural landscapes. Similar values of gamma-diversity over all land use categories implied a countrywide homogenized dragonfly fauna, which is probably caused by historic land use. Main conclusions Our results indicate that land use is a relevant driver for the composition of freshwater species at the landscape scale. Urban landscapes maintain species diversity better than agricultural landscapes, but they modify the species composition. Additional research on the effects of land use change is required to understand species responses and predict future distributions in a changing world in order to plan sustainable conservation strategies.