Cited research Proc. R. Soc. B doi:10.1098/rspb.2010.1004 (2010)

How many species of flowering plant are there? Around 400,000, estimate Stuart Pimm at Duke University in Durham, North Carolina, and his colleagues. They first modelled the pace of taxonomic research, knowing that as the pool of undiscovered species shrinks, taxonomists take more time to make the same number of discoveries. So changing rates of discovery per taxonomist hint at the number of unknown species. Then they asked experienced taxonomists how many species they thought were still undiscovered.

Both methods suggested that the number of unnamed species is about 10–20% of the number of described species and that many are likely to be rare, localized and under threat, the authors say. E.M.