Land use is more important than climate for species richness and composition of bat assemblages on a regional scale

The decline of bat populations across Europe has generated considerable interest and activities for the conservation of this enigmatic group of mammals. However, the factors influencing their distribution and species richness are still poorly understood, particularly on regional scales. We used the presence/absence data of the bat atlas of the German federal state of Bavaria (grid cell area ∼34 km2) to estimate the species–area curve and to compare the predictive power of environmental and climatic data sets for species richness and composition of bat assemblages within grid cells. We used as predictors land-use data extracted from CORINE, and climatic information from the WorldClim database. We found a species–area relationship with a slope very similar to that of other vertebrate assemblages (S = 2.56 × A0.209). By using variance partitioning for species richness and predictive canonical correspondence analysis, we found that on the scale considered, land use is more important than climate for bat assemblages. Nevertheless, the amount of explained variance is low. Concentrating on the land-use data, we found that the relative amount of the grid cell area dominated by human activities (e.g., settlements, traffic) was associated with increasing species richness as well as the probability of occurrence of several single bat species. Furthermore, broadleaf forests and mixed forests increased species richness, and even small proportions (>5%) of these land-use types within a grid cell are sufficient for a positive influence on species richness. Our results underline the importance of urban areas for the conservation of bats on regional scales. Furthermore, the results underline the importance of small forest patches as habitats for bats.