The IUCN Red List of Threatened Species, established in 1964 by the International Union for Conservation of Nature (IUCN), is the most comprehensive global inventory of the conservation status of animal, plant, and fungi species.

It goes beyond being just a classification of species. It serves as a critical barometer of the planet’s biodiversity health and plays a key role in policy-making, biodiversity conservation, and resource management.

Purpose and Importance

Global Biodiversity Health Indicator: It reflects the extinction risk of species worldwide.
Informs Conservation Decisions: Provides essential data on:
- Geographic range
- Population trends
- Habitat and ecological needs
- Human use and trade
- Threats and pressures
- Recommended conservation actions
Policy Impact: Supports evidence-based environmental policy and international agreements (e.g., CBD, CITES).
Highlight the magnitude of global biodiversity loss.

Who assesses species for The IUCN Red List?

The IUCN Red List relies on Assessors (trained individuals, usually species experts) to assess species based on the currently available data and information. This comes from a range of sources, including published scientific papers, books, reports, expert knowledge, indigenous knowledge and citizen science. Red List Authorities review the assessments, and then the IUCN Red List Unit checks the assessments before publishing them on The IUCN Red List website

The IUCN Red List Categories and Criteria

The IUCN Red List Categories and Criteria are intended to be an easily and widely understood system for classifying species at high risk of global extinction. It divides species into nine categories: Not Evaluated, Data Deficient, Least Concern, Near Threatened, Vulnerable, Endangered, Critically Endangered, Extinct in the Wild and Extinct.

Not Evaluated (NE)
- A taxon is Not Evaluated (NE) when it has not yet been evaluated against the criteria.Not Evaluated (NE) species are not published on the IUCN Red List
Data Deficient (DD)
- A taxon is Data Deficient (DD) 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. A taxon in this category may be well studied, and its biology well known, but appropriate data on abundance and/or distribution are lacking.
Least Concern (LC)
- A taxon is Least Concern (LC) when it has been evaluated against the Red List criteria and does not qualify for Critically Endangered, Endangered, Vulnerable or Near Threatened.
Near Threatened (NT)
- A taxon is Near Threatened (NT) 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.
Vulnerable (VU)
- A taxon is Vulnerable when the best available evidence indicates that it meets any of the criteria for Vulnerable i.e.
- Criteria
  - reduction in population (> 50% over the last 10 years)
  - population size estimated to number fewer than 10,000 mature individuals,
  - probability of extinction in wild is at least 10% within 100 years, and
  - it is therefore considered to be facing a high risk of extinction in the wild.
Endangered (EN)
- A taxon is Endangered (EN) when the best available evidence indicates that it meets any of the criteria A to E for Endangered, and it is therefore considered to be facing a very high risk of extinction in the wild.
- A taxon is Endangered when the best available evidence indicates that it meets any of the criteria for Endangered.
- Criteria
  - reduction in population size (70% over the last 10 years),
  - population size estimated to number fewer than 250 mature individuals
  - quantitative analysis showing the probability of extinc-tion in wild in at least 20% within 20 years.
Critically Endangered (CR)
- A taxon is Critically Endangered when the best available evidence indicates that it meets any of the criteria for Critically Endangered.
- Criteria
  - reduction in population (> 90% over the last 10 years),
  - population size (number less than 50 mature indi-viduals),
  - quantitative analysis showing the probability of extinc-tion in wild in at least 50% in their 10 years) and
  - it is therefore considered to be facing an extremely high risk of extinction in the wild.
Extinct in the Wild (EW)
- A taxon is Extinct in the Wild (EW) when it is known only to survive in cultivation, in captivity or as a naturalized population (or populations) well outside the past range. A taxon is presumed Extinct in the Wild when exhaustive surveys in known and/or expected habitat, at appropriate times (diurnal, seasonal, annual), throughout its historic range have failed to record an individual. Surveys should be over a time frame appropriate to the taxon’s life cycle and life form.
Extinct (EX)
- A taxon is Extinct (EX) when there is no reasonable doubt that the last individual has died. A taxon is presumed Extinct when exhaustive surveys in known and/or expected habitat, at appropriate times (diurnal, seasonal, annual), throughout its historic range have failed to record an individual. Surveys should be over a time frame appropriate to the taxon’s life cycle and life form.

What taxa are included on The IUCN Red List?

Animals, plant and fungi species, subspecies, varieties (plants only) and subpopulations can be assessed on the Red List. However, an assessment of the animal, plant or fungi at the species level is required before subspecies, varieties and subpopulations can be assessed.
The listing of undescribed species is discouraged, but can be included in exceptional circumstances where there is a clear conservation benefit.
Hybrids of species, domesticated taxa and micro-organisms are not included on the Red List.

How often are species reassessed on The IUCN Red List?

Although The IUCN Red List is updated twice a year, this does not mean that all species are assessed twice a year or even every year. We aim to assess species every 5–10 years, depending on factors such as data availability, conservation concern, and capacity.
However, there is no fixed schedule, and some species may be reassessed sooner if new information becomes available.
Birds that are Data Deficient (DD) or Critically Endangered (CR) are assessed on a yearly basis by BirdLife Internationa

The IUCN Red List is more than just a catalogue of endangered species—it is a global warning system. By systematically evaluating the conservation status of species, it helps highlight the increasing pressures on biodiversity caused by human activities. As a scientifically credible and globally recognized tool, it guides governments, conservationists, and policymakers to take timely action to prevent extinction, restore ecosystems, and preserve the planet’s biological heritage. In an era of accelerating biodiversity loss, the IUCN Red List is not just relevant—it is indispensable for ensuring a sustainable and resilient future for all life on Earth.

FAQs on IUCN Red List

Q1. What is the IUCN Red List?

The IUCN Red List is a global inventory of the conservation status of plant and animal species, assessing their extinction risk.

Q2. Who publishes the Red Data Book?

The International Union for Conservation of Nature (IUCN) publishes the Red Data Book.

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