Taxonomic uncertainty and the challenge of estimating global species richness

Abstract

It is a biogeographical trope that after several centuries of explora-tion, our knowledge of the world's biodiversity is still staggeringly incomplete (Meyer et al., 2016), even for well-studied groups such as trees (Keppel et al., 2021). Thus, when a study publishes a new esti-mate of the number of known (and unknown) tree species on Earth, it often gains global media attention. Recently, a new study suggested that there were approximately 73,000 tree species worldwide and as much as 14% of the world's tree flora still remains unknown to science (Gatti et al., 2022). But how accurate are such estimates?