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International audience; Compared to green spaces, the ecological value of built elements has been largely ignored despite representing the main land cover in cities. In streets, pavements are linear built elements which are omnipresent in all neighborhood types and which extend over large cumulative areas in cities. We assessed the capacity of pavements to promote spontaneous flora and investigated the drivers of pavement plant assemblages. Based on a plant survey along 48 km of pavements in a French city which no longer uses pesticides, we examined the relative importance of multi-scale factors (i.e. landscape context, pavement characteristics and frequency of manual weeding) on different aspects of pavement plant communities including total plant cover, species richness and beta-diversity. More than 300 species were recorded. Plant assemblages were mainly determined by the pavement type, plant cover and species richness being much higher on sandy than on asphalt pavements. There were marked differences in species composition between pavement types with many more species associated with sandy than with asphalt pavements. We found a higher species richness and plant cover on pavements located in commercial and industrial areas than in residential neighborhoods. The effects of weeding frequency and the presence of green space around pavements were marginally important. We demonstrate that pavements with a high level of permeability play a major role in promoting urban biodiversity which should be taken into account by urban planners. We recommend that ecologists work with civil engineers and landscape architects to develop new urban ecological designs. © 2019 Elsevier B.V.

Urbanisation leads to natural habitats being fragmented with various effects according to the species and their ecological characteristics. Paradoxically, the urbanisation process creates relatively unused environments, wastelands, habitats which could contribute to biodiversity conservation in urban regions. In this review we examined the role of wastelands in maintaining biodiversity in the city and assessed the different factors responsible for wasteland biodiversity. 37 articles were suitable for our aim. Most of the studies have been conducted in large cities in Western and Central Europe. A wasteland is defined as an abandoned site with spontaneous vegetation (i.e. wild grown vegetation). In most cases, wastelands harbour more species than other urban green spaces. The processes which affect the biodiversity of wastelands operate on two different levels. Locally, the area size, age, soil, microclimate and the vegetation structure are the dominant factors. As in other environments, the species richness increases with the size of the wasteland. Wastelands of different ages include different stages of vegetation, ranging from pioneer to pre-forest stages, and consequently harbour different communities of plants and animals. The diversity of anthropogenic soil substrates leads to different plant communities. At the landscape scale, matrix composition and geographic connectivity between wastelands influence the biodiversity of wastelands, although to a lesser extent than the local features. We show that wastelands have a real potential to contribute to biodiversity conservation in urban regions. At the city scale, they represent habitats which urban planners need to take into account and include in dynamic urban planning.