Urbanisation Is Related to the Prevalence of Threatened Species on Islands Across the Globe

ABSTRACT Aim To assess how environmental characteristics and human impacts contribute to the global prevalence of threatened bird species on islands (the ratio of threatened to non‐threatened species per island), and to identify which types of land use are most strongly associated with extinction risk on islands. Location Global. Time Period Present‐day extant species and land‐use patterns. Major Taxa Studied Terrestrial birds. Methods We compiled bird species occurrence and conservation status data from BirdLife International and eBird, and environmental and land‐use variables for islands. We grouped nine predictor variables into three categories: island characteristics (e.g., area, isolation, climate), human impacts (urban cover, cropland, human appropriation of NPP (HANPP)), and wildlands (intact habitat). We used model selection and BIC‐based model weights to evaluate the relative support for each variable group and assessed which factors best explained the prevalence of threatened species. Results Models including both island characteristics and human impact variables explained ~40% of the variation in the prevalence of threatened bird species across islands. The strongest predictor overall was island type: threatened species prevalence was significantly higher on oceanic islands than on continental islands. Among human impact variables, urban land cover had the most substantial effect, with threatened species prevalence up to five times greater on highly urbanised islands. Main Conclusions The prevalence of currently threatened species across islands is shaped by the interplay between environmental conditions and anthropogenic pressures. Our findings highlight urbanisation as a particularly potent driver of extinction risk, especially on oceanic islands. We suggest that island biogeography frameworks be updated to explicitly account for human‐driven impacts, as island ecosystems are increasingly reshaped by global land‐use transformations.