Urbanization, historical connectivity and socioeconomic status shape multispecies grassland diversity in a metropolitan region

Urbanization poses complex challenges and opportunities for biodiversity conservation, yet most studies rely on single taxa or a limited set of environmental dimensions. We calculated multispecies-diversity and abundance for 49 extensively managed dry grassland sites across an urban-to-rural gradient in Berlin, Germany, encompassing 13 taxonomic groups from primary producers to a top predator and 158 Red-listed species. We evaluated the relative influence of urban structure (impervious surface cover, patch size, habitat connectivity), environmental factors (air temperature, non-native plant cover), socioeconomic context (composite social index), and historical landscape configuration (historical connectivity) on total multispecies richness and abundance, as well as on Red-listed species richness. Historical connectivity was the strongest predictor for Red-listed species richness, indicating that many urban populations persist as relicts and may be subject to extinction debt. Impervious surface cover showed a nonlinear effect on total diversity, with substantial declines only beyond 40% coverage, suggesting conservation opportunities up to moderate development. Socioeconomic status positively influenced all multispecies measures (indices), consistent with the luxury effect, whereas 2D and 3D connectivity exhibited neutral and negative association with total multispecies richness and abundance. Patch size was important for Red-listed species but not for total multispecies diversity, while local temperature and non-native plant cover were not significantly related to any diversity index. Overall, biodiversity responses to urbanization were context-dependent and nonlinear, and often differed between total and Red-listed multispecies diversity. Consequently, urban conservation planning requires multidimensional approaches that integrate historical land-use legacies, socioeconomic conditions, and historical connectivity to support both common and endangered species in cities.