Organization of Information

Previous editions of the IUCN Red List have been produced in book format. The 2000 Red List marked a radical departure from the traditional approach. The reasons for this departure are simple:

  • The decision to incorporate plants and animals into a single Red List, rather than treating them separately, meant that the total species coverage more than doubled in 2000, and continues to increase with each update of the Red List.
  • The 2000 Red List marked the start of a process to document all species listed. This documentation greatly increases the size but also the utility of the Red List.
  • The IUCN Red List now makes better use of the electronic medium as it provides a wider audience with easy access to the information.
  • The Red List will be updated on an annual basis from 2000 onwards, and so the production of a book every year would be too prohibitive both in terms of time and cost.
The IUCN Red List of Threatened Species is available only as an electronic version on the World Wide Web. A CD-ROM version of the Red List was produced in 2000 and funds permitting, a new version will be produced in the future. The information presented is based on data extracted from the SSC Species Information Service (SIS) Red List database maintained by the IUCN SSC Red List Programme Office in Cambridge, UK. The information provided here covers all taxa that have been assigned an IUCN Red List Category with the exception of those designated as Not Evaluated (NE). All the assessments presented, except those for geographically isolated subpopulations or stocks, are for the taxon (species, subspecies or variety) as a whole (i.e. they indicate the global risk of extinction). No national or regional Red List assessments are included, except for national extinctions (where known) and an occasional note about national or sub-national status in one of the documentation fields.

Documentation of Species

The SSC Red List Programme has developed a set of minimum documentation requirements that were introduced in 2000. People making submissions to the Red List are requested to provide (in addition to the usual details about name, status, criteria and distribution) a rationale to support the listing, a map of the extent of occurrence, a list of the major habitats the species is found in, what the major threats are, an indication as to whether the species' population trend is increasing, decreasing, stable or unknown, what conservation actions are in place or are needed and information on the utilization of the species. If the taxon assessed falls within the jurisdiction of an appointed Red List Authority (see details in the IUCN/SSC Red List Programme) then it will be referred to them for evaluation.

The documentation on the Detailed Results page for each taxon attempts to cover the following:

  • Higher taxonomy details recorded including Kingdom, Phylum, Class, Order and Family.
  • Scientific name including authority details wherever possible. (Note: for animals the date of description is usually shown, but for plants this is not the case).
  • Common names in English (E), French (F) and Spanish (S).
  • Red List Category and Criteria (only the criteria which were met for the highest category to which the species can be assigned are specified, not all the other criteria met as is done by BirdLife International in their publications).
  • Date of assessment (used to show the year a species was last assessed).
  • An indication if a petition about the status of the species has been lodged and is pending a decision from the Red List Standards and Petitions Subcommittee (see This is indicated on the web site by the letter 'P' as a flag in the Annotation field on the initial search results page. The Annotation field is only present when there is a petition.
  • Links to assessments of subspecies, varieties or subpopulations if present.
  • Red List History (a history of global listings for the taxon concerned on the IUCN Red Lists and BirdLife lists – this is a work in progress).
  • Countries of occurrence and sub-country units for large countries and islands far from mainland countries (see below).
  • Occurrence in marine regions and inland water bodies or systems (see below).
  • A map of the extent of occurrence (not currently shown on the web site).
  • A rationale for the listing (including any numerical data used, or inferences made, that relate to the thresholds in the criteria).
  • Current population trends (where = improving, = deteriorating, = stable and = uncertain or don't know, while a blank indicates that this has not been looked at yet).
  • Major habitat preferences.
  • Major threats (past, present and future).
  • Conservation actions in place and needed.
  • The utilization of the species (this information is being captured but is not shown on the current version of the web site).
  • General notes about population and range, habitat and ecology, threats, what conservation measures are in place or needed, and comments on the utilization of the taxon.
  • Information on any changes in the Red List status of the taxon, and why this status has changed (not shown on the web site).
  • Links to other web sites which may contain further information and images of the taxon concerned.
  • Data sources (published and unpublished).
  • Consultation process (including the name/s of the assessor/s who had made the original assessment, and if a Red List Authority (RLA) was involved, the names of at least two individual evaluators and the RLA involved).
The degree of documentation achieved is extremely variable across the list, but an increasing number of species are meeting the minimum requirements. For those people wishing to submit a Red List assessment for inclusion on the Red List, a standard questionnaire has been produced to guide assessors through the documentation requirements. The questionnaire can be downloaded from It is not mandatory to use this form when submitting assessments. The questionnaire is very lengthy because of the inclusion of the complete set of Authority Files. Users need only fill in those parts relevant to their taxon and can ignore or even delete those parts of the Authority Files that do not apply.

Extinct and Extinct in the Wild Species

For Extinct species, extra documentation is required indicating the effective date of extinction, the causes of the extinction and the details of surveys which have been conducted to search for the species. The starting date for the inclusion of extinctions was previously set at 1600 AD, but this has been moved back to 1500 AD to be in line with the starting date used by the Committee on Recently Extinct Organisms. An attempt has been made to collate whatever information is available on each Extinct species and this is presented in the various documentation fields.

Subspecies, Varieties and Subpopulations

Although the name IUCN Red List of Threatened Species implies that the primary focus is at the species level, the IUCN Red List also includes assessments that are done at the infra-specific or subpopulation levels. Ideally, for such taxa to be included in the Red List, the global status of the species itself should be assessed. In most instances this is the case and generally these are assessed as Least Concern (LR/lc or LC). There are some cases, however, especially amongst the plants where this has not been done and it may well be that some of these species warrant a threatened status. For subpopulations (also called stocks), only geographically isolated subpopulations, between which there is little genetic exchange (typically one migrant individual or gamete per year), are included on the IUCN Red List.

In the 2000 version of the Red List, all searches produced combined results for species, subspecies, varieties and subpopulations. In many cases users only wanted species-level information and if the lists were very long this was often difficult to extract. The default search options now provide results at the species level only. Searches for subspecies, varieties and subpopulations have to be specified separately. If assessments for subspecies, varieties or subpopulations are available, these are clearly indicated from the detailed results pages of the species concerned.

Taxa Removed from the Red List

The Red List is highly dynamic with species moving on and off for a variety of reasons. The main reason for removals is changes in taxonomy. All changes are tracked, so that a complete audit trail is kept for each taxon name that ever appears on the Red List. Taxa removed from the Red List for taxonomic reasons (i.e. they are considered synonyms of other taxa) are currently not searchable or shown in a separate list. Requests for further information about these taxa can be directed to the Red List Programme Office (

Distribution Information

Distribution is recorded in terms of country names following the 5th edition (and subsequent web updates) of the ISO-3166-1 standard (ISO 1997). Unless geographically very remote from each other, islands and other territories are included with the parent country. In the case of species that inhabit islands significantly distant from the mainland, the island name is given in parentheses (e.g., Spain (Canary Islands)). The naming of such islands follows edition 2 of the World Geographical Scheme for Recording Plant Distributions (Brummitt et al. 2001) prepared for the International Working Group on Taxonomic Databases (TDWG). The TDWG geographic system also provides a standard set of Basic Recording Units (BRU) that are sub-country units based on provinces or states. The BRU's are used to subdivide very large countries like Australia, Brazil, China, South Africa, the Russian Federation and the United States of America, etc. into smaller more conveniently sized units for recording distributions. This system has been adopted for the IUCN Red List wherever possible. Most plant taxa on the Red List have had their distributions recorded down to BRU level where appropriate, but unfortunately sub-country information is still lacking for most of the animal species. Hence this feature is not currently searchable. Each country or territory has also been assigned to a single geographic region to enable users to search by larger geographic areas. (View the list of Countries by Regions).

The distributions of some species in certain countries have not been confirmed. These are indicated as possibly doubtful occurrences by the inclusion of a '?' after the country name. These instances are distinct from vagrant distributions that are displayed as definite occurrences, i.e. vagrant distribution records are not specifically flagged. So care should be taken when using the distribution information for subsequent analyses. Likewise, for a number of very widespread Least Concern taxa, the list of country occurrences may be incomplete or in some instances not even recorded (e.g., Mus musculus ) because such taxa are virtually cosmopolitan. Please note that the results presented in the published analyses of the Red List data (Baillie et al. 2004, Hilton-Taylor 2000), do not include questionable distribution records and vagrant distributions. Similarly the summary statistics tables do not include any questionable distribution records.

For marine species, country records have been provided wherever possible. This information has been derived from a number of sources, e.g. FishBase and the many FAO publications. Any species without a country name in the Red List, is not included in any of the analyses or tables presented. For some marine species, especially those that are most strictly marine, their distributions are also shown as generalized ranges in terms of the FAO Fishing Areas, indicated as follows (e.g., Atlantic-eastern central). For many inland water species, usually those restricted to a single water system, inland water ranges are also given with a clear indication from the name if it is a river or a lake. In a few instances, a second river name (e.g. Colorado River, Concho River) indicates a section of the drainage in which the species occurs. In most cases, the countries in which these freshwater species occur are also recorded, but there are a few instances (e.g., cichlid fish in Lake Victoria), where the precise country distribution is unknown, so the only distribution information is the Lake name.

In most cases where a species is known to have been introduced or reintroduced to a country, this is indicated by an [int] or [re-int] after the country name in the distribution text. Note that for searches on threatened species in a specific country or group of countries, the introduced species are excluded from the results. Whereas a search for a particular threatened species, will list the countries where it has been introduced. Where populations are known or suspected to have been extirpated from a country, this is indicated by [RE] or [RE?] for Regionally Extinct or possibly Regionally Extinct.

Geopolitical events during recent years may have led to some inconsistency or errors in the distribution information provided. Within reasonable limits every effort has been made to determine which of the new nations that were part of the former Czechoslovakia, Yugoslavia and USSR support species previously attributed to the larger unit. There may be some species in the database that have still not been fully resolved. Adherence to the ISO system also creates some problems, as there is often a time lag between a political change and a new ISO code being allocated for the new country. The version of the ISO codes used for example, maintains Hong Kong and Macao as separate units.

The Red List contains assessments for some stocks or geographically isolated subpopulations. In the 1996 Red List these were indicated by (S) after the species name, but this created confusion in some cases, so a geographic name is now given directly after the name of the species e.g., Balaena mysticetus (Spitsbergen stock).