Urbanisation is related to the prevalence of threatened species on islands across the globe

Aim To assess how environmental characteristics and human impacts
contribute to the global prevalence of threatened bird species on islands
globally, and to identify which types of anthropogenic 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, alongside
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), and wildlands (intact habitat). Using model
selection and BIC-based model weights, we evaluated the relative support
for each variable group and assessed which factors best explained the
prevalence of threatened species (i.e., the proportion of threatened to
non-threatened species per island). Results Models including both island
characteristics and human impact variables explained ~40% of the variation
in the prevalence of currently threatened bird species across islands. The
strongest predictor overall was island type: oceanic islands exhibited
significantly higher threatened species prevalence than continental
islands. Among human impact variables, urban land cover had the most
substantial effect, with highly urbanized islands showing up to a
five-fold increase in threatened species prevalence. Main conclusions The
prevalence of currently threatened species across islands is shaped by the
interplay between environmental conditions and anthropogenic pressures.
Our findings highlight urbanization as a particularly potent driver of
extinction risk, especially on oceanic islands. This study underscores the
need to update island biogeography frameworks to explicitly account for
human-driven impacts, as island ecosystems are increasingly reshaped by
global land-use transformations.