Global wetland biodiversity declines and compositional shifts under urbanization

Abstract Urbanization is rapidly transforming wetlands worldwide, threatening biodiversity. The lack of a global synthesis of wetland biodiversity responses to urbanization hinders biodiversity-informed urban planning. We conduct a global meta-analysis, quantifying wetland biodiversity responses to urbanization (343 comparisons of urbanized and non-urbanized reference sites from 124 studies). Wetland biodiversity loss is substantial – with urbanization causing local loss of one in three taxa and reducing Shannon diversity by ~ 25%. Declines were pervasive across spatial scales, national wealth indicators and the intactness of reference locations, but greatest for river and amphibian communities. Urbanization significantly altered species composition, especially for tropical rainforest and fish communities, but did not consistently drive biotic homogenization. Evidence was concentrated in temperate and high-income regions, highlighting critical knowledge gaps in biodiverse tropical and low-income regions. These findings reveal context-dependent biodiversity responses to urbanization, identifying habitat and taxa with the greatest sensitivity to urban development, informing wetland conservation worldwide.