Traits determine plant interactions with each other and their environment and the “Raunkiærian shortfall” in plant trait knowledge limits many scientific endeavors. Spatial patterns of this shortfall may contribute to erroneous conclusions. Thus, there is an urgent need to assess spatial completeness of plant trait data, understand drivers of geographic biases, and identify solutions for filling regional gaps.
To address this need, we combined a comprehensive set of regional species checklists for vascular plants with data for 2,027 traits across 128,929 species to assess trait completeness across the globe. We compared the Raunkiærian shortfall with the Wallacean (distributional) and the Darwinian (phylogenetic) shortfalls and tested whether trait completeness correlates with emerging anthropogenic changes. We found that trait completeness is associated with socioeconomic and biological factors influencing sampling likelihood: completeness was positively associated with mean species range size, research expenditure, and human population density and negatively associated with endemism and richness. Trait completeness was significantly correlated with climate change, human footprint, and phylogenetic completeness, but was not significantly correlated with biodiversity intactness or distributional completeness. Integration of a second, regional trait database (AusTraits) more than doubled completeness in Australia, indicating that the creation and integration of regional databases can rapidly expand trait completeness.