The urban tree of life: quantifying relationships between body size and urban tolerance for more than 30,000 plant and animal species

Urbanization is a major global driver of biodiversity change, with species responses to urban settings ranging from avoidance to exploitation. To better understand these responses, we conducted a global analysis of urban tolerance across more than 30,000 animal and plant species, with a focus on body size—an ecological trait fundamental to space use, mobility, metabolism, and environmental sensitivity. Our synthesis showed a consistent pattern across taxa and biogeographic regions: many species are urban avoiders, while few thrive as urban exploiters—a pattern we coin “Species Urbanness Distribution”. We further found that larger body sizes were generally associated with greater urban tolerance in plants compared to animals, though these size-tolerance relationships showed considerable variability among families. Our findings highlight the heterogeneous relationship between body size and urban tolerance across the tree of life, underscoring the importance of tailored strategies to support urban biodiversity. This research advances ecological understanding of urban filtering and provides a framework for guiding biodiversity-sensitive urban planning amid accelerating global urbanization.