Evidence item

To evaluate these alternatives, we synthesize population trends for species initially rare or common across assemblages from 4748 sites within 129 studies spanning terrestrial, freshwater, and marine ecosystems. We quantify how population trends relate to initial abundances using hierarchical Bayesian models that account for regression to the mean and include realm, taxon, and environmental covariates. We find consistently stronger declines among formerly common species in marine and terrestrial assemblages, while freshwater assemblages show no clear directional pattern. Rare species present at the start also decline, but less so than common species, while colonists that were not present at the start of the time series compensate for losses within the rarest abundance category.