Urban sprawl or how urbanized land spreads over the landscape: Implications for biodiversity conservation

Abstract

Urban growth seriously threatens biodiversity worldwide. I present an exhaustive review of the impacts of urban sprawl on biodiversity. In particular, I focus on the relative contributions of distinct components of urban sprawl (i.e., urban area, dispersion degree and land use intensity) to the impacts on biodiversity for different taxonomic and ecological groups classified according to species characteristics and functional traits that are expected to be sensitive to urbanization. I also show how functional structure and assembly patterns of biological communities respond to urbanization at broad spatial scales. Urban sprawl mostly relates to the homogenization of species assemblages. Urban area has the strongest impacts, but the intensity of urban land use and the degree of dispersion of urban areas significantly contributes to these impacts. Responses to urbanization are greatly affected by species mobility, specialization degree and their interaction. Urbanization modifies community assembly patterns and drives marked trait-dependent compositional changes in species assemblages. This results in biotic homogenization, low functional redundancy and diversity levels, and potentially reduces ecological resilience. Impacts of urban sprawl impacts are expected to be especially harmful when it reaches sites of high conservation value due to the species and habitats they host, such as protected areas. I present an analysis of the degree of urbanization in Natura 2000 protected sites over the recent past, which shows an incipient urban sprawl into this protection network.