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IUCN Red List

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IUCN stands for the International Union for Conservation of Nature. When it was first formed in 1948, it went by the International Union for the Protection of Nature and Natural Resources and, later, from 1990 to 2008, the World Conservation Union. Its headquarters are in Switzerland; however, it is an international organisation, employing approximately 1,000 full-time staff from over 50 countries. The IUCN's mission is to:

influence, encourage and assist societies throughout the world to conserve nature and to ensure that any use of natural resources is equitable and ecologically sustainable.

Its primary focus is attempting to influence governments, businesses and other stakeholders to take action. It does this through building relationships and education. It is best known to the general public for creating the IUCN red list of threatened species. These include Amphibians, Mammals, Conifers, Birds, Sharks & Rays, Reef Corals, Selected Crustaceans, Reptiles and Cycads.

IUCN red list of threatened species

The IUCN red list was established to educate the public and policymakers on the urgent conservation issues that face us today.

According to the IUCN, the Red List goals include:

  • providing information that can guide actions taken to conserve biological diversity

  • drawing attention to the magnitude and importance of threatened biodiversity

  • providing scientifically-based information on the status of species and subspecies at a global level to influence national as well as international policy and decision-making

In short, the IUCN Red List helps to inform conservation and funding priorities.

It is known to be the most comprehensive source of information on the world's fungus, animal and plant extinction risk status.

It is a vital indicator of biodiversity in the world.

There are more than 142,500 species on The IUCN Red List, and over 40,000 species within that number are threatened with extinction.

How is it used?

The list is used by many organisations, including:

  • International agreements

The IUCN Red list guides decision-making on an international scale.

For example, it is used in agreements such as the UN Sustainable development goals.

  • World Bank Group Performance Standard PS6

This is an internationally recognised standard of good practice in terms of companies adhering to standards that minimise the impact on biodiversity. It uses the IUCN Red list to reduce damage from large-scale infrastructure and natural resource extraction projects to the environment.

  • Government agencies

Government agencies use data from IUCN red lists to guide their policies.

An example of this is National Parks regulations.

  • Zoos

Zoos can use the categories to educate the public regarding the status of species.

  • Scientists

The IUCN red list is a primary data source for publications and analysis.

  • Teachers and students

The list is used to educate the next generation of conservationists.

  • Journalists

Journalists use the red list to inform their work.

IUCN partnership

The IUCN Red List of threatened species is compiled thanks to the red list partners and their networks. These include the following:

  1. IUCN - the International Union for Conservation of Nature. It brings governments, NGOs, the UN, international conventions and companies together to develop biodiversity policy, laws and best practices.

  1. SCC - the Species Survival Commission is the most prominent volunteer commission in the IUCN and has a global membership of around 10,000 experts.

  1. ASU - Arizona State University Centre for biodiversity outcomes is ranked number 1 in the United States for innovation.

  1. BirdLife - this is the world's most significant nature conservation Partnership.

  1. BGCI - the Botanic Gardens Conservation International is an international organisation that aims to conserve threatened plants globally. It has over 700 members in 118 countries.

  1. NatureServe - this non-profit conservation organisation aims to give a scientific basis for effective conservation action.

  1. The Royal Botanic Gardens Kew - is a world-famous organisation with immense expertise in plant diversity, conservation and sustainable development in the UK and worldwide.

  1. ZSL - the Zoological Society of London (ZSL) conserve animals and their habitats and educates the public on conservation.

  1. Sapienza University of Rome - this is a public research university located n Rome and is part of the partnership.

IUCN Red List Criteria

IUCN Red List Categories and Criteria were developed for use at the global level but can also be used at national and regional levels.

Alt text IUCN red list chart living environmentFigure 1. Summary of criteria A-E. Source: icunredlist.org.

Criteria A to E

There are five quantitative criteria that are used to determine if a taxon is threatened.

(There are three categories of threatened - Critically Endangered, Endangered or Vulnerable)

The five criteria are:

A. Declining population (past, present and/or projected)

B. Geographic range size and fragmentation, decline or fluctuations

C. Small population size and fragmentation, decline, or fluctuations

D. Very small population or very restricted distribution

E. Quantitative analysis of extinction risk (e.g., Population Viability Analysis)

It is important to note that not all criteria are appropriate to all taxa assessed. Therefore:

  • All of the taxa undergoing assessment must be evaluated against all criteria.
  • Even just meeting one criterion qualifies a taxon for listing at that threat level.
  • All criteria met at the highest threat level need to be listed.


A vital part of red list assessment is documentation, and high standards must be met. The documentation justifies the categories that taxa are put in and allows analysis of the data produced. The red list is a scientific publication, so scientific paper standards must be maintained. Additionally, correct documentation enables informed reassessments.

This is important as the scientific paper informs big decisions regarding conservation worldwide.

According to the IUCN, the information required for documentation is:

  1. Scientific name

  2. Higher taxonomy details (Kingdom, Phylum, Class, Order, Family)

  3. Taxonomic authorities for all specific and infra-specific names used, following the appropriate nomenclatural rules

  4. IUCN Red List Category and Criteria (including sub-criteria) met at the highest category of threat

  5. A rationale for the Red List assessment

  6. Data for parameters triggering the Red List Criteria met at the highest Category level

  7. Countries of occurrence

  8. Geo-referenced distribution data for all taxa with a known distribution

  9. The direction of the current population trend (stable, increasing, decreasing, unknown)

  10. Coding for occurrence in freshwater (= inland waters), terrestrial, and marine ecosystems (i.e., “System” in SIS)

  11. Suitable habitats utilised (coded to the lowest level in Habitats Classification Scheme)

  12. Bibliography (cited in full; including unpublished data sources but not personal communications)

  13. Names and contact details of the Assessor(s) and at least one reviewer

Put more simply, this is Taxonomy including authority details, Common names, Red List Category and Criteria, Countries of Occurrence, Map of distribution, The rationale for the assessment, Habitat preferences, Major Threats, Conservation measures in place & measures needed, Citations list, Reasons for any category changes, Names of assessors.

IUCN red list categories

The IUCN Red List Categories and Criteria are designed to be an easy-to-understand framework for identifying species at high risk of extinction worldwide. The nine categories in which species are classified are:

Not Evaluated Not evaluated (NE)

A taxon is not evaluated when it has yet to be assessed against the criteria.

Data Deficient (DD)

When there is insufficient data to establish a direct or indirect evaluation of a taxon's danger of extinction based on its range and/or population state, it is considered Data Deficient. A taxon in this category may have been carefully investigated, and its biology is well understood, but there is a lack of data on abundance and/or distribution. As a result, Data Deficient is not a category of threat.

Taxa listed in this category imply that additional information is needed and that future studies may prove that threatened classification is warranted. It is critical to make the best possible use of whatever data is accessible. In many circumstances, selecting data deficient and a threatened status should be done with caution. If a taxon's range is known to be relatively limited, or if a significant length of time has passed since the taxon's last record, the endangered status may be warranted.

An example of this is the Chilean round ray Urobatis marmoratus. It was last described in the literature in 1892 from a single specimen, and no other instance has been reported; therefore, the description of this species is incomplete.

Least Concern (LC)

A taxon is of the least concern when evaluated against the criteria and does not qualify for any other categories. The taxa in this category are the most abundant and widespread.

An example is the Kiang / Tibetan Wild Ass, the largest of all African and Asian wild asses found in China, India, Nepal and Pakistan. Its coat is reddish in summer to dark brown in winter with almost white underparts. It has short ears, a large tail tuft and broad hooves, meaning it is seen as closer to a horse than an ass.

Near Threatened (NT)

A near-threatened taxon has been evaluated against criteria A to E. Still, it does not qualify for critically endangered, endangered or vulnerable but, soon, has a high chance of qualifying for a threatened category.

An example is the Markhor goat, found in the mountains of central Asia, with populations also throughout northeastern Afghanistan, northern India and Pakistan.

Vulnerable (VU)

When the best available information suggests that a taxon fulfils any criteria A to E for vulnerable, it is deemed to be facing a high risk of extinction in the wild.

An example is the Leatherback sea turtle, the 4th heaviest modern reptile and the largest of all living turtles. It lacks a bony shell, hence the name. Instead, it is covered by skin and oily flesh.

Endangered (EN)

When the best available information suggests that a taxon fulfils any of the Endangered criteria A to E, it is deemed to be facing a very high risk of extinction in the wild.

An example is the Himalayan musk deer. These deers lack antlers but possess a pair of enlarged and easily broken canines that grow continuously, reaching a maximum length of 10 cm. The musk the males secrete from a gland in their abdomen is used to manufacture perfumes and medicines.

Critically Endangered (CR)

A taxon is Critically Endangered when the best evidence indicates that it meets any criteria A to E for Critically Endangered. Therefore, it is considered to be facing an extremely high risk of extinction in the wild.

An example is the Sociable Lapwing, a winter migrant to India found in fallow fields and scrub desert. It is native to Central Asia, South Asia some countries in the Middle East.

Extinct in the Wild (EW)

When a taxon is only known to survive in captivity or cultivation, it is considered extinct in the wild (as the name says, it no longer lives in the wild). It can only be presumed extinct in the wild when exhaustive surveys have been carried out in its habitat at appropriate times and have failed to record the species.

Surveys should be over a time frame appropriate to the taxon's life cycle and life form.

An example is the black softshell turtle, a freshwater turtle found in India (Assam) and Bangladesh (Chittagong and Sylhet).

Extinct (EX)

If there's no reasonable doubt that the last individual of a taxon has died, the taxon is considered extinct. When extensive searches in known and/or predicted habitat, at relevant periods (diurnal, seasonal, yearly), throughout a taxon's historic range have failed to record an individual, the taxon is deemed extinct.

Surveys should be conducted over a time corresponding to the taxon's life cycle and life form.

One of the most famous extinctions that humans caused is in Dodos. Dutch sailors first mentioned the dodo in the late 16th century. They were last seen in 1662!

Ever noticed on specific wildlife conservation television adverts that a particular species is used to catch the attention of the public and the conservation efforts? These are known as flagship species.

Flagship species are species which are on the verge of extinction, such as the Giant Panda or the African Elephant.

Many of these flagship species face threats to survival via human intervention, such as poaching and habitat destruction for things such as farming and tourism. These animals must be protected, and conservation efforts focus on their distribution or population dispersal.

Population dispersal is a process that involves living organisms expanding the territory or range in which they live.

IUCN red list chart

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

ICUN red list chart living environment StudySmarterFigure 2. The proportion of extant species in The IUCN Red List of Threatened Species. Source: iucnredlist.org.

IUCN Red List - Key takeaways

  • IUCN stands for International Union for Conservation of Nature

  • More than 142,500 species have been assessed for The IUCN Red List, with 40,000 species threatened with extinction. To be on the Red list, specific criteria must be met.

  • It is the world's most comprehensive information source for the extinction risk of species.

  • It is a compilation of the conservation status of species globally and is used internationally to inform and influence biodiversity conservation.

  • It is generated through the knowledge of thousands of the world's leading scientists through an extensive review process published in an online scientific journal.

Frequently Asked Questions about IUCN Red List

To date, more than 142,500 species have been assessed for The IUCN Red List with 40,000 species threatened with extinction.

The International Union for Conservation of Nature’s Red List of Threatened Species

A. Declining population (past, present and/or projected)

B. Geographic range size, and fragmentation, decline or fluctuations

C. Small population size and fragmentation, decline, or fluctuations

D. Very small population or very restricted distribution

E. Quantitative analysis of extinction risk (e.g., Population Viability Analysis)


Amphibians, Mammals, Conifers, Birds, Sharks & Rays, Reef Corals, Selected Crustaceans, Reptiles and Cycads. 

Final IUCN Red List Quiz

IUCN Red List Quiz - Teste dein Wissen


What does not evaluated (NE) mean? 

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Has not yet been evaluated against the criteria.

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What does data deficient (DD) mean? 

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Not enough data to make an assessment of its risk of extinction.

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What does least concern (LC) mean? 

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Lowest risk. Does not qualify for a more at-risk category. Widespread and abundant taxa are included in this category.

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What does near threatened Near threatened (NT) mean? 

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Likely to become endangered in the near future.

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What does vulnerable (VU) mean? 

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High risk of endangerment in the wild.

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What does endangered (EN) mean?

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Very likely to become extinct in the near future

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What does critically endangered (CR) mean? 

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Extremely high risk of extinction in the wild.

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What does extinct in the wild (EW) mean? 

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Known only to survive in captivity, or as a naturalized population outside its historic range.

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What does Extinct (EX) mean? 

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No known individuals remaining.

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What does Threatened mean?

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A grouping of three categories: Critically Endangered, Endangered, and Vulnerable.

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How many categories are there?

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Show question


True or false - Data deficient is a category of threat?

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Why is correct documentation important?

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The scientific paper informs big decisions regarding conservation across the world and correct documentation enables informed reassessments.

Show question


Name an IUCN partner.

Show answer


Any from the following: Arizona State University, BirdLife International, Botanic Gardens Conservation International, Conservation International, International Union for Conservation of Nature (IUCN), NatureServe, Royal Botanic Gardens Kew, Sapienza University of Rome, IUCN Species Survival Commission, Texas A&M University, and Zoological Society of London.

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Give an example of a flagship species

Show answer


African Elephant

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