Conserving our global botanical heritage:The PSESP plant conservation program

摘要

It is a fundamental truth of ecology that most species are rare.And this rarity extends beyondmeasures of abundance to geographic distribution.In a global context,very few species are truly abundant,and most are more or less restricted geographically.In the world of plants,where there are several hundred thousand species,the number of species with especially small population sizes and small fragmentary ranges is extremely large.One recent assessment,the most exhaustive undertaken so far,based on 200 million observations taken from herbarium records,ecological surveys and other sources,suggests that of the more than 400,000 species of land plants,ca.36%are“exceedingly rare”(Enquist et al.,2019).