The numbers of species listed in each category in The IUCN Red List of Threatened SpeciesTM change each time the Red List is updated. This is a result of various factors, including species being assessed and added to the Red List for the first time, species being reassessed and moving into a different category of threat, and taxonomic revisions causing the total number of recognised species within a group to change. Summaries of the numbers of species in each Red List Category by taxonomic group and by country are provided here for the current version of The IUCN Red List.
All of the statistics presented in the following tables and figures are for species only (i.e., they do not include subspecies, varieties or geographically isolated subpopulations or stocks). More detailed analyses of specific taxonomic groups and the results of regional assessment projects carried out by IUCN can be found in the Initiatives section. For detailed results of assessments for marine species, see the Global Marine Species Assessment web site.
|Trends in the status of biodiversity||How many species are threatened?|
|Threatened species in past and present Red Lists||Red List category changes|
|Summaries by taxonomic group||Endemic species by country|
|Summaries by country|
The numbers of species appearing in each category of threat in The IUCN Red List change each time the Red List is updated. In order to monitor the status of biodiversity, it is important to reassess species periodically. This reassessment may result in species moving into a different Red List Category for non-genuine or genuine reasons:
IUCN relies on valuable research from around the world to provide new and better information for species. Each category change on the Red List has the reasons for the change recorded, which allows us to quickly identify species that are genuinely improving or deteriorating in status. Each time the Red List is updated, a list of species that have changed category is provided along with the reasons for these changes (Table 7).
With many different reasons for species changing status on the IUCN Red List (see the section A dynamic Red List: reasons for status changes above), it is impossible to determine any meaningful trends in the status of biodiversity simply by looking at overall changes in numbers of threatened species between Red List updates. For this reason, the figures presented in Table 1 and Table 2 for numbers of threatened species in each IUCN Red List since 1996 must be interpreted with exteme care; these figures illustrate increasing assessment efforts by IUCN and its Partners since 1996, helping to refine our current understanding of the status of biodiversity (see the secton An expanding Red List: knowledge gaps and fully assessed groups below), rather than showing genuine status changes over time.
To disentangle the effects of increased effort invested in assessing species, and to focus only on genuine status changes (i.e., species that have genuinely improved or deteriorated in status), IUCN developed the Red List Index (RLI) - see the Red List Overview page (section Development of the IUCN Red List as an Indicator of Biodiversity Trends) for more information on the RLI. The RLI provides a clearer view of real trends within different taxonomic groups, and for biodiversity as a whole.
Currently, the RLI is available for four taxonomic groups only (those in which all species have been assessed at least twice): birds, mammals, amphibians, and corals (see Figure 1 and the CBD publication Global Biodiversity Outlook-3). It has also been aggregated into a single index for those four groups (see Butchart et al. 2010 - use the link from Science Article: Global Biodiversity: Indicators of Recent Declines. May 2010). The RLI clearly demonstrates that the status of these major groups is still declining. An increasing number of national RLIs are now being used by countries to monitor biodiversity loss (see BirdLife International 2012).
Figure 1. RLIs for reef-forming corals, birds, mammals, and amphibians. Coral species are moving towards increased extinction risk most rapidly, while amphibians are, on average, the most threatened group. An RLI value of 1.0 equates to all species qualifying as Least Concern (i.e., not expected to become Extinct in the near future). An RLI value of 0 equates to all species having gone Extinct. A constant RLI value over time indicates that the overall extinction risk for the group is constant. If the rate of biodiversity loss were reducing, the RLI would show an upward trend.
In addition to species changing status, The IUCN Red List grows larger with each update as newly described species and species from the less well-known groups are assessed for the first time (Figure 2). IUCN and its partners are working to expand the number of taxonomic groups that have full and complete Red List assessments in order to improve our knowledge of the status of the world's biodiversity.
Figure 2. Increase in the number of species assessed for The IUCN Red List of Threatened SpeciesTM (2000–2012.2).
Not all taxonomic groups have been completely assessed (Table 1, Figure 3). It is important to consider this when looking at the numbers of species in each Red List Category; although The IUCN Red List gives a good snapshot of the current status of species, it should not be interpreted as a full and complete assessment of the world's biodiversity. Currently the main gaps in coverage on the Red List that IUCN and its partners are working on are plants, invertebrates, and freshwater and marine species (for more information on expanding taxonomic coverage on the Red List, see the Red List Overview section).
Species assessed as Critically Endangered (CR), Endangered (EN), or Vulnerable (VU) are referred to as "threatened" species. Reporting the proportion of threatened species on the Red List is complicated by the fact that not all species groups have been fully evaluated, and also by the fact that some species have so little information available that they can only be assessed as Data Deficient (DD). For many of the incompletely evaluated groups, assessment efforts have focused on species that are likely to be threatened; therefore any percentage of threatened species reported for these groups would be heavily biased (i.e., the % threatened species would likely be an overestimate).
For those groups that have been comprehensively evaluated, the proportion of threatened species can be calculated, but the number of threatened species is often uncertain because it is not known whether DD species are actually threatened or not. Some taxonomic groups are much better known that others (i.e., they will have fewer DD species), and therefore a more accurate figure for proportion of threatened species can be calculated. Other, less well known groups have a large proportion of DD species, which brings uncertainty into the estimate for proportion of threatened species.
To account for the issues raised above, proportion of threatened species is only reported for the more completely evaluated groups (i.e., >90% of species evaluated). Also, the reported percentage of threatened species for each group is presented as a best estimate within a range of possible values bounded by lower and upper estimates:
Note that since extinction risk has been evaluated for less than 5% of the world's described species (see Table 1), IUCN cannot provide an overall estimate for how many of the planet's species are threatened. However, overall figures for numbers of species currently assessed in each Red List Category, along with an indication of which groups have been more comprehensively evaluated, can be found in the summary statistics tables below (Tables 1 to 8).
An overview of proportions of threatened species within each of the more comprehensively assessed groups is shown in Figure 3. Note that this figure compares data for very different groups of species ranging from ecosystem groups (e.g., reef-forming corals) to whole classes (e.g., mammals, birds). The intention of Figure 3 is to present a summary of assessments for groups that have been comprehensively evaluated through the various projects carried out by IUCN, IUCN SSC Specialist Groups, and Red List Partners. Groups containing fewer than 150 species (e.g., sturgeons (27 species), mangroves (67 species), seagrasses (72 species), seasnakes (110 species), etc.) have been excluded from this figure as they are far too small to be compared with the larger groups. For more details on those species groups, please contact the IUCN Red List Unit.
Figure 3. The proportion of extant (i.e., excluding Extinct) species in The IUCN Red List of Threatened Species. Version 2012.2 assessed in each category for the more comprehensively assessed groups. Taxa are ordered according to the horizontal red lines, which show the best estimate for proportion of extant species considered threatened (CR, EN, or VU). Best estimates of percentage threatened species (with lower and upper estimates) for each group are: cycads 63% (63-64%); amphibians 41% (30-56%); reef-forming corals 33% (27-44%); sharks & rays 31% (16-63%); freshwater crabs 31% (16-65%); conifers 30% (29-33%); mammals 25% (21-36%); groupers 18% (12-43%); birds 13% (13-14%); wrasses 5% (4-18%); lobsters <1% (0-35%). The numbers above each bar represent the total number of extant species assessed for each group. CR - Critically Endangered, EN - Endangered, VU - Vulnerable, NT - Near Threatened, DD - Data Deficient, LC - Least Concern.
Tables 1 and 2 are organized by taxonomic group and show numbers of threatened species listed in all of the IUCN Red Lists since 1996. These should be consulted to see a summary of overall changes in numbers of threatened species over recent years, however please note that there are many different reasons for these figures changing between different versions of the Red List (see A Dynamic Red List: reasons for status changes above).
Table 1 - Numbers of threatened species by major groups of organisms (1996–2012)
Table 2 - Changes in numbers of species in the threatened categories (CR, EN, VU) from 1996 to 2012
Tables 3 and 4 are organized primarily by taxonomic group; these should be consulted for example, to see a summary of the number of mammals assessed as threatened (table 4 is an expanded version of table 3).
Table 3a - Summary of number of animal species in each Red List Category in each taxonomic class
Tables 3b & 3c - Summary of number of plant species in each Red List Category in each taxonomic class
Table 4a - Number of species in each Red List Category in each major animal taxonomic group (Class, Order)
Table 4b - Number of species in each Red List Category in each major plant taxonomic group (Class, Family)
Tables 5 and 6 are organized primarily by country; these should be consulted for example, to obtain a summary of the number of threatened mammals in any particular country.
Prior to 2003, the country tables presented on the Red List omitted certain wide-ranging marine species because they did not have country records in the database at the time. Since the release of the 2003 Red List, country records have been provided for marine species, where data are available, therefore, these also appear in the country tables (tables 5 and 6).
In the 2006 and previous Red Lists, the country tables displayed figures for species with confirmed and unconfirmed distributions within a country to match the figures obtained from a search of the web site. Since 2007, the Red List default search on specific countries or regions includes only certain distributions, reintroduced species and regionally extinct species (i.e., the default search excludes all uncertain distributions, introduced species and vagrant records). Users have also been provided with the option of including uncertain distributions, introduced species and vagrant species in their search if they wish, but the figures shown in the tables below will match the figures from a default search of the web site only.
Table 5 - Number of threatened species in each major group of organisms in each country (Critically Endangered, Endangered and Vulnerable categories only).
Table 6a - Number of extinct, threatened and other species of animals in each Red List Category in each country.
Table 6b - Number of extinct, threatened and other species of plants in each Red List Category in each country
Table 7 is organized primarily by taxonomic group; this table should be consulted to check which species have changed Red List status since the previous Red List update and the main reason for the status change.
Table 7 - Species changing IUCN Red List Category.
Table 8 is similar to the country tables (tables 5 and 6), but focuses on endemic species only (i.e., species occurring naturally within one country only) and only presents figures for species groups that have been completely assessed. This table should be consulted, for example to check total number of endemic mammals and number of threatened endemic mammals within a particular country.
Table 8 - Total endemic and threatened endemic species in each country (totals by taxonomic group). Table 8 coming soon.