Significance Forecasts of global change impacts on biodiversity often assume that the current geographical distributions of species match their ecological niches. Here we examine this assumption using an extensive dataset of large-scale variation in demographic rates that enables us to quantify demography-based ecological niches of 26 plant species. Contrasting these niches with the species’ geographic distributions reveals that niche–distribution mismatches can be large and depend on key life-history traits: poorly dispersed species are absent from suitable sites, and species with high persistence ability are present in sites that are currently unsuitable for them. Such niche–distribution mismatches need to be accounted for to improve forecasts of biodiversity dynamics under environmental change.