Biodiversity hotspots house most undiscovered plant species.

For most organisms, the number of described species considerably

underestimates how many exist. This is itself a problem and causes

secondary complications given present high rates of species extinction.

Known numbers of flowering plants form the basis of biodiversity

“hotspots”—places where high levels of endemism and

habitat loss coincide to produce high extinction rates. Howdifferent

would conservation priorities be if the catalog were complete? Approximately

15% more species of flowering plant are likely still undiscovered.

They are almost certainly rare, and depending on where

they live, suffer high risks of extinction from habitat loss and global

climate disruption. By using a model that incorporates taxonomic

effort over time, regions predicted to contain large numbers of undiscovered

species are already conservation priorities. Our results

leave global conservation priorities more or less intact, but suggest

considerably higher levels of species imperilment than previously

acknowledged.