The Role of Urban Structures in the Distribution of Wasteland Flora in

Wastelands are likely to host a significant part of urban floristic diversity but have received limited attention because they are not considered inter-esting green zones. Here, we explore the potential role of wastelands in maintaining urban biodiver-sity to help define effective urban management plans. We quantified floristic diversity in 98 wasteland sites of Hauts-de-Seine, one of the most densely populated areas in France, and character-ized the environmental parameters and spatial distribution of sites to identify some of the factors that influence plant species composition and to explore the impact of urban environment on the floristic interest of wastelands. Their floristic rich-ness represented 58 % of the total richness observed in the whole study area. Site richness depended on site area (the largest sites were the richest) and site age, with a maximum in sites of intermediate age (4–13 years). In the largest sites only (>2,500 m2), the floristic distance among sites was positively correlated with geographic distance, which suggests that migration of species among large sites partly controls local floristic composition. In contrast, the environmental distance among sites was not cor-related with floristic distance. Finally, we showed that the presence of collective and individual dwellings within 200 m of a wasteland decreased its floristic rarity, whereas the presence of rivers or ponds increased it. We derive several recommen-dations to optimize the management of wastelands with respect to conservation of urban biodiversity