Urban refugia enhance persistence of an endemic keystone species facing a rapidly spreading invasive predator

Urbanization shapes global biodiversity, often driving biodiversity loss and biotic homogenization. However, urban areas could paradoxically enhance conservation by acting as refugia for declining populations due to other global change components, such as biological invasions. Despite growing interest in the potential of urban areas to promote biodiversity conservation, the lack of robust empirical studies unveiling how urban refugia emerge and contribute to species persistence hinders our ability to leverage urban areas to minimize global biodiversity loss. In this study, we examined whether and how urban areas promote the persistence of a keystone Mediterranean island endemic lizard (Podarcis pityusensis) threatened by the invasive snake Hemorrhois hippocrepis. Using field transects and citizen science data, we found that while invasive snakes strongly drive local lizard extirpation, urbanization buffers this effect and supports local population persistence. Intensive snake trapping further revealed that urbanization acts as an ecological filter, hindering snake spread into urban centers. Finally, our population dynamics model shows that, contrary to a source-sink model, urban lizard populations can persist in the mid-term without the arrival of new individuals. Our findings effectively help uncover how urban areas can effectively act as refugia for threatened species, emphasizing their importance in global biodiversity conservation strategies.