Stropp, J., Ladle, R.J., Emilio, T., Lessa, T. & Hortal, J. (2022) Taxonomic uncertainty and the challenge of estimating global species richness. Journal of Biogeography, 49, 1654-1656. doi:10.1111/jbi.14463

Assessments of the global number of tree species vary between 45,000 and 100,000. The disparity in the estimates triggered a scientific debate about the most appropriate method and data to identify the total number of tree species. Much progress has been made in understanding the sensitivity of estimates to different mathematical models (e.g. parametric or non-parametric estimators), and the homogeneity and completeness of taxonomic data. Surprisingly, there has been little progress in quantifying uncertainty associated with the underlying data, specifically related to changes in taxonomy and errors in species identification. Here we highlight two reasons why understanding of taxonomic uncertainty is crucial for estimating the number of known and unknown species in the world. First, taxonomy does not advance homogeneously across taxa or regions. Second, species misidentification is common across taxa and prevalent in temperate and tropical forest plots. Expeditions to remote forests are surely needed to unveil the diversity of the world’s tree flora, but uncovering the number of known and unknown tree species also requires bridging the gap between taxonomy and macroecology. In the age of advanced data mining and statistical modelling, reconstructing centuries of taxonomic discoveries may be as rewarding as new field expeditions.