Recommendations for the use of critical terms when applying IUCN red-listing criteria to bryophytes

Abstract

The IUCN Red List of threatened species is widely recognised as an objective system to assess the extinction risk of animals, plants and fungi, as a global indicator of the threats to biodiversity and as an authoritative tool to catalyse conservation actions (Rodrigues et al. 2006, Mace et al. 2008). To date, Red Lists according to the red-listing system of IUCN (2012a) have been established for many different taxonomic groups at various geographical scales (< www.iucnredlist.org>) although they were originally designed for application at the global level (IUCN 2012b). According to the IUCN red-listing system, species are grouped into one of the following nine categories: Extinct [EX], Extinct in the Wild [EW], Critically Endangered [CR], Endangered [EN], Vulnerable [VU], Near Threatened [NT], Least Concern [LC], Data Deficient [DD] and Not Evaluated [NE]. The Red List categories CR, EN and VU, collectively referred to as ‘threat categories’, are assigned to species (or subspecies or varieties in certain cases) on the basis of five quantitative criteria (IUCN 2012b) that have been developed to estimate the extinction risk to each species assessed. Guidelines for the application of these criteria are regularly updated (IUCN SPSC 2017).