Risk of extinction of plant communities: Risk and assessment categories

There are many proposals for the assessment of plant communities, based on different criteria, but very few proposals for categorization of the risk of extinction of plant communities (syntaxa). In this paper, concepts related to extent of occurence (EOO), area of occupancy (AOO), extinction and regeneration of plant communities are defined. Also, we propose and define several ranks of extinction risk based on quantitative criteria of the EOO, AOO and processes of decline. The proposals are global, for application to any type of cormophytic vegetation, without geographical restrictions. To check the adequacy of the proposed ranks and its thresholds, the method has been applied to the vegetation of the Iberian Peninsula based on the EOO (122 plant communities) and the AOO (2224 plant communities).