The IUCN Red List Categories and Criteria

The IUCN Red List lists species according to their estimated risk of extinction. In national or regional Red Lists, species are assigned one of eleven threat Categories (see Table 1 and here). These Categories indicate the conservation status of the species, whereby species that are categorised as Critically Endangered, Endangered or Vulnerable are considered to be threatened species, i.e. their extinction is imminent.

Table 1. Definition of IUCN Red List Categories.

Category Clarification
EXTINCT (EX) A taxon is Extinct when, after exhaustive surveys, there is no reasonable doubt that the last individual has died.
EXTINCT IN THE WILD (EW) A taxon is Extinct in the Wild when, after exhaustive surveys, it is known only to survive in cultivation, in captivity or as a naturalized population (or populations) well outside the past range.
REGIONALLY EXTINCT (RE) A taxon is Regionally Extinct when it is extinct within the region but extant in other parts of the world.
CRITICALLY ENDANGERED (CR) A taxon is Critically Endangered when the best available evidence indicates that it is facing an extremely high risk of extinction in the wild, based on it meeting any of the criteria A to E for Critically Endangered.
ENDANGERED (EN) A taxon is Endangered when the best available evidence indicates that it is facing a very high risk of extinction in the wild, based on it meeting any of the criteria A to E for Endangered,
VULNERABLE (VU) A taxon is Vulnerable when the best available evidence indicates that it is facing a high risk of extinction in the wild, based on it meeting any of the criteria A to E for Vulnerable.
NEAR THREATENED (NT) A taxon is Near Threatened when it has been evaluated against the criteria but does not qualify for Critically Endangered, Endangered or Vulnerable now, but is close to qualifying for or is likely to qualify for a threatened category in the near future.
LEAST CONCERN (LC) A taxon is Least Concern when it has been evaluated against the criteria and does not qualify for Critically Endangered, Endangered, Vulnerable or Near Threatened. Widespread and abundant taxa are included in this category.
DATA DEFICIENT (DD) A taxon is Data Deficient when there is inadequate information to make a direct, or indirect, assessment of its risk of extinction based on its distribution and/or population status.
NOT EVALUATED (NE) A taxon is Not Evaluated when it has not yet been evaluated against the criteria.
NOT APPLICABLE (NA) A taxon may be categorised as Not Applicable in a number of cases: widespread taxa that occur at very low numbers in the region, taxa occurring only in captive populations, invasive species, or vagrants.

Red List Index

To assess the conservation status of species, the IUCN Red List uses a set of five criteria (A-E) related to population size, geographic range, and rates of decline that are applicable across the whole taxonomic range of species (see Box 1, and more details here). The criteria are developed for quantitative evaluation of extinction risk, but allow for several levels of uncertainty to be accounted for in the assessment process. Applying the system to a species eventually yields an objective, comprehensive summary of its conservation status.

Box 1 – IUCN Red List Criteria
Criterion A evaluates whether a reduction in population size of 30% or more has occurred over 3 generations or 10 years (whichever is longer). The reduction can be measured from any point in the past to any point in the future, depending on available data, and may be inferred from habitat or exploitation data. The larger the reduction is, the higher the threat category will be.
Criterion B evaluates whether the geographic distribution of the species is small and/or fragmented, taking into account any continuing declines in distribution, population size or habitat extent and/or quality.
Criterion C requires that the population size of the species is small from the onset, and takes into account continuing declines, as well as the spread of the individuals over subpopulations.
Criterion D is used for evaluating species that have an extremely small population size (e.g. <1,000 individuals worldwide), and typically have a very restricted geographic distribution.
Criterion E uses a quantitative analysis of the extinction risk of a species. The higher the probability for the species to become extinct within certain frames, the higher its threat category will be.

National assessments

In contrast to global assessments, regional or national assessments need to account for neighbouring populations and non-resident taxa. There are additional guidelines set out by IUCN for such assessments. A species’ conservation status within a country or region may differ from its global Red List status because extinction risk is not uniform across the species range. However, when a species is endemic to the country, its national assessment will determine its global conservation status.

The National Red List Process

Red List assessments based on the IUCN methodology need to follow proper scientific practice and are subject to peer-review. This is true for the global assessments as well as the national assessments. A typical IUCN Red List assessment process generally consists of a number of steps:

  1. Pre-assessment: an overview of all available nation-wide information for the species to be assessed is compiled.
  2. Assessment: the information is used to assess the extinction risk of the species according to the IUCN Criteria and to assign the relevant Category. The assessment process is thoroughly documented, such that decisions and assumptions can be evaluated during the review process.
  3. Review and consistency check: the assessment is checked by independent reviewers for proper application of the criteria, proper application of scientific standards and consistent interpretation of Red List terms and definitions.
  4. Publication: the Red List website is updated at pre-set intervals and any new assessments will be published during the next update.

Supporting information – Red List assessments need to be extensively documented and require descriptive as well as quantitative information. The IUCN Red List Criteria themselves are quantitative in nature, and each Criterion depends on one or more specific types of data.

Box 2 – Required supporting information for IUCN Red List assessment

Required information Purpose
1.       Scientific name To identify which taxon is being assessed
2.       Higher taxonomy details
3.       Taxonomic authority
4.       IUCN Red List Category and Criteria To identify and justify the current status of the taxon

To allow basic analysis

5.       Rationale for the Red List assessment
6.      Data that show that the Red List Criteria have been met
7.       Areas of occurrence
8.       Geo-referenced distribution data
9.       Direction of population trend
10.    Ecosystem
11.    Suitable habitat utilised
12.    Bibliography Provide all sources of data and information used
13.    Details of assessors and reviewers To acknowledge those involved

To demonstrate the appropriateness of the assessment and review process

Data management – Following the Red List assessments, the assigned Categories and Criteria from all assessments, as well as their complete documentation are ideally stored in a database that can be updated as the need arises. Currently, the National Red List assessments are stored and managed in IUCN’s global Species Information Service (SIS). Information is extracted from the SIS and presented on this website.

Roles in the Red List process – While a legal framework for the National Red List is in place in North Macedonia, a framework for planning and implementing the Red List assessments, e.g. a Red List steering committee, is currently absent. To conduct individual species assessments in practice, three types of involvement are needed: contributors, assessors and reviewers. Contributors are persons or national institutions that provide data, but are not involved in conducting the actual assessment. Assessors are usually national experts on certain taxonomic groups that are conducting the assessments, and usually also provide at least part of the data. Ideally, assessors are trained by IUCN to properly apply the IUCN Red List Categories and Criteria at the national level. Reviewers are preferably experts on the species for which they are reviewing the assessment, but of primary importance is their familiarity with the IUCN Red List methodology.

IUCN ECARO has been involved in the first phase of the National Red List as a surrogate steering committee in order to provide guidance and training throughout the process. It produced a “National Red Lists for Species Conservation in North Macedonia”, and conducted a 4-day Red List Assessor training workshop in Skopje in April 2018. Thirty-five experts from NGOs, universities, private sector and government in North Macedonia, Bosnia and Herzegovina, and Croatia attended the workshop, supporting the exchange of red-listing experience from across the region. Using lectures, hands-on group-work tasks and knowledge tests, the workshop provided the participants with an in-depth understanding of the process of assessing the extinction risk of species, covering the data requirements, the assessments methodology, available tools, spatial representation, and data management options. A discussion session on how the newly gained information can be used to guide the national red-listing process in the country was held, forming a basis for chalking out the further process. IUCN remains available to be involved in future efforts.

 IUCN Red List Assessor Training Workshop participants working on an assessment exercise.
Photo: Maarten Hofman/IUCN
IUCN Red List Assessor Training Workshop participant explaining a species assessment during an exercise.
Photo: Maarten Hofman/IUCN
IUCN Red List Assessor Training Workshop trainers from the IUCN Red List Unit in Cambridge, UK, during the Macedonian workshop.
Photo: Maarten Hofman/IUCN

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