Plant Species Numbers

Even today the number of plant species currently in existence is not clear. New species are still being identified and calculating anything like an accurate number is further complicated by the many examples of the same species in different areas being known by different names. Target 1 of the GSPC calls for “a widely accessible working list of know plant species, as a step towards a complete world flora, and it is expected that the working list will be complete by 2008. In the meantime, the best estimate we have of the number of known plant species is around 400,000.

How many of these plant species are under threat is also unclear. In 1997, the World Conservation Union’s (IUCN) Red List of Plants included some 34,000 threatened species (out of 60,000 evaluated). Since then, the IUCN Red Listing criteria have changed, and only around 11,000 species have been evaluated with the new system. However, of those evaluated, some 8,000 species were found to be under threat. Both of these assessments indicate that well over half of all plants evaluated are at risk. At the national level, we know that around 20% of the UK’s flora is threatened. A global estimate of one in four plant species being under threat of extinction is therefore reasonable.

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