Estimating the Size of the World's Threatened Flora

Abstract

). Here we estimate themissing tropical data from global patternsof plant endemism. The results suggest thatas many as half of the world’s plant speciesmay qualify as threatened with extinctionunder the World Conservation Union(IUCN) classification scheme.Comprehensive Red Lists for plants areavailable for only a scattering of tropicalcountries, making it difficult to assess thetrue scale of the global conservation crisisfor plants. We have approximated the miss-ing tropical data by observing that the num-ber of plant species endemic to a country isa reasonable proxy for the number of glo-bally threatened plant species in that coun-try. In European countries, the former is astrong predictor of the latter (