The International Union for Conservation of Nature (IUCN) Red List of Threatened Species was increasingly used during the 1980s to assess the conservation status of species for policy and planning purposes. This use stimulated the development of a new set of quantitative criteria for listing species in the categories of threat: critically endangered, endangered, and vulnerable. These criteria, which were intended to be applicable to all species except microorganisms, were part of a broader system for classifying threatened species and were fully implemented by IUCN in 2000. The system and the criteria have been widely used by conservation practitioners and scientists and now underpin one indicator being used to assess the Convention on Biological Diversity 2010 biodiversity target. We describe the process and the technical background to the IUCN Red List system. The criteria refer to fundamental biological processes underlying population decline and extinction. But given major differences between species, the threatening processes affecting them, and the paucity of knowledge relating to most species, the IUCN system had to be both broad and flexible to be applicable to the majority of described species. The system was designed to measure the symptoms of extinction risk, and uses 5 independent criteria relating to aspects of population loss and decline of range size. A species is assigned to a threat category if it meets the quantitative threshold for at least one criterion. The criteria and the accompanying rules and guidelines used by IUCN are intended to increase the consistency, transparency, and validity of its categorization system, but it necessitates some compromises that affect the applicability of the system and the species lists that result. In particular, choices were made over the assessment of uncertainty, poorly known species, depleted species, population decline, restricted ranges, and rarity; all of these affect the way red lists should be viewed and used. Processes related to priority setting and the development of national red lists need to take account of some assumptions in the formulation of the criteria.

https://www.alces.ca/references/download/268/Quantification-of-Extinction-Risk-IUCNs-System-for-Classifying-Threatened-Species.pdf

Quantification of Extinction Risk: IUCN's System for Classifying Threatened Species

Leaf wax n-alkane distributions in and across modern plants: Implications for paleoecology and chemotaxonomy

Cucurbitacins and cucurbitane glycosides: structures and biological activities

Composition of Plant Cuticular Waxes

Natural Science Foundation of China[30000213, 30370160, 30670214]; National Basic Research Program of China (973 Program)[2009CB522300]; Chinese Academy of Sciences

Roy Osborne

Papers

Cucurbitane triterpenoids from the leaves of Momordica foetida

The world cycad census and a proposed revision of the threatened species status for cycad taxa

The magical and medicinal usage of Stangeria eriopus in South Africa.

Jessic acid and related acid triterpenoids from combretum elaeagnoides

Limonoids and triterpenoid acids from the bark of Entandrophragma delevoyi