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Summary Statistics

Summary Statistics

The numbers of species listed in each Red List Category change each time The IUCN Red List is updated. For each Red List update, IUCN provides summaries of the numbers of species in each category, by taxonomic group and by country.

 

To download the Summary Statistics Tables, click here.

The number of species listed in each IUCN Red List Category change over time because:

  • species are constantly being assessed and added to The IUCN Red List for the first time;
  • other species are being reassessed resulting in some moving into different Red List Categories; and
  • taxonomic revisions result in the total number of recognised species within a group changing.

 

All of the statistics presented in the summary tables 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 can be found in the Resources & Publications section or in the regional pages for Europe, the Mediterranean, the Gulf of Mexico, and the Persian Gulf.

 

A dynamic Red List: reasons for changing status

In order to monitor the changing status of biodiversity, it is essential to reassess species periodically. This reassessment may result in species moving into a different Red List Category for non-genuine or genuine reasons:

Non-genuine reasons

  • New information has become available since the last assessment (e.g., more recent data are available on population sizes, threatening processes, rates of decline or recovery, etc.).
  • There has been a taxonomic revision resulting in the species no longer being the same concept as it was before (e.g., it is now split into several species each with smaller ranges, population sizes, etc.; or it has been merged with other species so the range, population size, etc. are now larger than they were previously).
  • An error has been discovered in the previous assessment (e.g., the wrong information was used; the IUCN Red List Categories and Criteria were applied incorrectly; etc.).
  • The previous assessment used an older version of the IUCN Red List Categories and Criteria and the reassessment uses the current criteria which have slightly different thresholds.

 

 

 

 

 

Genuine reasons

  • The main threats are no longer present, or conservation measures (e.g., reintroduction, habitat protection or restoration, legal protection, harvest management, etc.) have successfully improved the status of the species enough to move it into a lower category of threat.
  • The main threats have continued unabated, have increased, or new threats have developed causing the status of the species to deteriorate enough to move it into a higher category of threat.

 

 

 

 

 

IUCN relies on research by scientists working around the world to make new and better species information available to allow Red List assessments to be updated and refined. All reassessments on The IUCN Red List include a record of the reasons for any change in Red List Category, and this allows us to identify which species are genuinely improving or deteriorating in status. Data for species that are genuinely changing status are used to calculate the Red List Index (RLI).

Table 7 shows the list of species that have changed category, along with the reasons for these changes.

 

An expanding Red List: knowledge gaps and fully assessed groups

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 1). 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; see the Barometer of Life page for more information about this work.

Figure 1. Increase in the number of species assessed for The IUCN Red List of Threatened SpeciesTM (2000–2018 (version 2018-2)).

Not all taxonomic groups have been completely assessed (see Table 1 and Figure 2). It is very important to consider this when looking at the numbers of species in each Red List Category and the proportions of threatened species within each group; 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. For more information the work underway to expand taxonomic coverage on The IUCN Red List, see the Barometer of Life page.

 

How many species are threatened?

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 IUCN Red List is complicated because:

  • not all species groups have been fully evaluated, and
  • 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 those 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., >80% of species have been 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:

  • Lower estimate = % threatened extant species if all DD species are not threatened, i.e., (CR + EN + VU) / (total assessed - EX)
  • Best estimate = % threatened extant species if DD species are equally threatened as data sufficient species, i.e., (CR + EN + VU) / (total assessed - EX - DD)
  • Upper estimate = % threatened extant species if all DD species are threatened, i.e., (CR + EN + VU + DD) / (total assessed - EX)

 

Note that since extinction risk has been evaluated for less than 5% of the world's described species (see Table 1), IUCN cannot provide a precise 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.

An overview of proportions of threatened species within each of the more comprehensively assessed groups is shown in Figure 2. Note that this bar chart groups comprehensively assessed groups of species into classes, with the exception of reef-forming corals (which is an ecosystem-based group that includes species from two separate classes: Anthozoa and Hydrozoa). The intention of this Figure 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 IUCN Red List Partners. Only groups containing at least 150 species are shown in Figure 2.

Figure 2. The proportion of extant (i.e., excluding Extinct) species in The IUCN Red List of Threatened Species. Version 2018-2 assessed in each category for the more comprehensively assessed (i.e., at least 80% of the group has been assessed) groups containing ≥150 species. Species are grouped into classes (with the exception of reef-forming corals, which includes species from classes Hydrozoa and Anthozoa), and are ordered according to the vertical red lines, which indicate 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 40% (31-53%); selected dicots (magnolias, birches and cacti) 35% (30-44%); selected reptiles (marine turtles, seasnakes, chameleons, crocodiles and alligators) 34% (29-44%); conifers 34% (34-35%); reef-forming corals 33% (27-44%); sharks & rays 31% (18-60%); selected crustaceans (lobsters, freshwater crabs, freshwater crayfishes and freshwater shrimps) 27% (17-56%); mammals 25% (22-36%); birds 14% (13.6-14.1%); selected gastropods (cone snails) 7.5% (6-20%); selected bony fishes (sturgeons, tunas, billfishes, blennies, pufferfishes, angelfishes, butterflyfishes, surgeonfishes, tarpons, ladyfishes, groupers, wrasses, seabreams, picarels, porgies, seahorses, pipefishes, trumpetfishes, shrimpfishes, cornetfishes, seamoths, and ghost pipefishes) 7% (6-20%); selected cephalopods (octopods) 4% (2-49%). The numbers to the right of each bar represent the total number of extant species assessed for each group. EW - Extinct in the Wild, CR - Critically Endangered, EN - Endangered, VU - Vulnerable, NT - Near Threatened, DD - Data Deficient, LC - Least Concern.

 

Summary Tables

 

Tables 1 & 2: Threatened species in past and present IUCN Red Lists

Tables 1 and 2 are organized by taxonomic group and show numbers of threatened species listed in each version of The IUCN Red List since 1996. These should be used 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 IUCN Red List (see A Dynamic Red List: reasons for changing status above).

  • Table 1 - Numbers of threatened species by major groups of organisms (1996–2018).

  • Table 2 - Changes in numbers of species in the threatened categories (CR, EN, VU) from 1996 to 2018.

 

Tables 3 & 4: Summaries by taxonomic group

Tables 3 and 4 are organized by taxonomic group. These should be used to see, for example, the numbers of globally threatened mammals, birds and amphibians (Table 4 is an expanded version of Table 3).

These tables include number of species tagged as 'Possibly Extinct' (CR(PE)) and 'Possibly Extinct in the Wild' (CR(PEW)). These figures are included to give an upper estimate for total number of recently extinct species on The IUCN Red List. Combining the total numbers of EX and EW species gives the total number of actual extinctions recorded (since 1500 AD); when CR(PE) and CR(PEW) species are also included, the resulting figure is an estimate of number of recent extinctions when uncertainty is taken into account.

  • Table 3a - Numbers of animal species in each IUCN Red List Category by Class.

  • Table 3b - Numbers of plant species in each IUCN Red List Category by Class.

  • Table 3c - Numbers of fungi and protist species in each IUCN Red List Category by Class.

  • Table 4a - Numbers of species in each IUCN Red List Category in each major animal taxonomic group (Class, Order).

  • Table 4b - Numbers of species in each IUCN Red List Category in each major plant taxonomic group (Class, Family).

  • Table 4c - Numbers of species in each IUCN Red List Category in each major fungi and protist taxonomic group (Class, Order).

 

Tables 5 & 6: Summaries by country

Tables 5 and 6 are organized by country. These should be used to see, for example, number of globally threatened mammals or the numbers of Critically Endangered species occurring within a specific country.

The figures presented in Tables 5 and 6 include only certain distributions, reintroduced species and regionally extinct species (i.e., the figures exclude all uncertain distributions, introduced species and vagrant records).

Important note: the figures presented in Tables 5 and 6 differ from the current default setting for country searches on the website. The website search currently includes ALL occurrences within each country (i.e., including introduced species, vagrant records, etc.) We are working towards ensuring the country figures presented in the statistics tables match the default search on the website.

For wide-ranging marine species, country records are provided in assessments only where data are available for this. These records are also included in Tables 5 and 6.

  • Table 5 - Numbers of threatened species (Critically Endangered, Endangered and Vulnerable categories only) in each major taxonomic group by country.

  • Table 6a - Numbers of animal species listed in each IUCN Red List Category by country.

  • Table 6b - Numbers of plant species listed in each IUCN Red List Category by country.

  • Table 6c - Numbers of fungi and protist species in each IUCN Red List Category by country.

 

Table 7: Species changing Red List Category

Table 7 is organized by taxonomic group. This table should be used 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 is provided here for the current Red List and for previous Red Lists (dating back to 2007).

Important Note: Table 7 is provided only to summarize the reasons for species changing category between one Red List update and the next. This table should not be used to calculate a Red List Index; for this it is necessary to analyse the underlying Red List data to identify genuine status changes between specific years for specific taxonomic groups.

 

Table 8: Endemic species by country

Table 8 is similar to the country tables (Tables 5 and 6), but focus on endemic species only (i.e., species occurring naturally within one country only). This table only presents figures for the more comprehensively assessed species groups (i.e., where >80% of the species in the group have been assessed). Table 8 should be used to check, for example the total number of endemic mammals and number of threatened endemic mammals within a specific country.

  • Table 8a - Total endemic and threatened endemic vertebrate species in each country for groups where >80% of species in the group have been assessed (totals by taxonomic group).

  • Table 8b - Total endemic and threatened endemic invertebrate species in each country for groups where >80% of species in the group have been assessed (totals by taxonomic group).

  • Table 8c - Total endemic and threatened endemic plant species in each country for groups where >80% of species in the group have been assessed (totals by taxonomic group).

 

Table 9: Possibly Extinct species

The number of recent extinctions documented by the Extinct (EX) and Extinct in the Wild (EW) categories on The IUCN Red List is likely to be a significant underestimate. The tags 'Possibly Extinct' and 'Possibly Extinct in the Wild' have therefore been developed to identify Critically Endangered species that are likely to already be extinct (or extinct in the wild), but for which confirmation is required.

Table 9 provides a list of all species that are flagged as 'Possibly Extinct' or 'Possibly Extinct in the Wild' in the current version of The IUCN Red List.

  • Table 9 - Possibly Extinct and Possibly Extinct in the Wild species.


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