Plant traits, biotopes and urbanization dynamics explain the survival of endangered urban plant populations.
With accelerating urbanization, the urban contribution to biodiversity conservation becomes increasingly important. Previous research shows that cities can host many endangered plant species. However, fundamental questions for urban nature conservation remain open: to what extent and where can endangered plant species persist in the long term and which mechanisms underlie population survival? We evaluate the survival of 858 precisely monitored populations of 179 endangered plant species in Berlin, Germany, by assessing population survival throughout different urban ecosystems over a period of 7.6 years on average. By linking population survival to various landscape variables and plant traits, we unravel the underlying drivers. More than one-third of populations went extinct during the observation period. Population survival was inversely correlated to the increase in impervious surfaces in the vicinity following the first 11 years after the fall of the Berlin wall. Additionally, populations in semi-natural habitats like forests and bogs were surprisingly more prone to local extinction than populations in anthropogenic habitats. Survival was highest for competitive species with a preference for drier soils (Ellenberg indicator for soil humidity). Synthesis and applications. Considerable levels of local population extinction demonstrate that the presence of endangered plants cannot be directly linked with their long-term survival in cities. However, the survival of remaining populations indicates opportunities for urban biodiversity conservation both within and outside conservation areas. The elucidated links between population survival, urbanization dynamics, biotope class and species traits support urban conservation strategies that reduce the proportion of impervious surface, prioritize conservation management in forests and grasslands and explore the opportunities of green spaces and built-up areas.