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Conservation status by IUCN Red List category
Extinct
Extinct (EX) (list) Extinct in the Wild (EW) (list)
Threatened
Critically Endangered (CR) (list) Endangered (EN) (list) Vulnerable (VU) (list)
Lower Risk
Near Threatened (NT) (list) Conservation Dependent (CD) (list) Least Concern (LC)
Other categories
Data Deficient (DD) (list) Not Evaluated (NE)
Related topics
International Union for Conservation of Nature (IUCN) IUCN Red List NatureServe status Lists of organisms by population
Comparison of Red List classes above and NatureServe status below
v t e

An IUCN Red List Critically Endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of the 157,190 species currently on the IUCN Red List, 9,760 of those are listed as Critically Endangered, with 1,302 being possibly extinct and 67 possibly extinct in the wild.

The IUCN Red List provides the public with information regarding the conservation status of animal, fungi, and plant species. It divides various species into seven different categories of conservation that are based on habitat range, population size, habitat, threats, etc. Each category represents a different level of global extinction risk. Species that are considered to be Critically Endangered are placed within the "Threatened" category.

As the IUCN Red List does not consider a species extinct until extensive targeted surveys have been conducted, species that are possibly extinct are still listed as Critically Endangered. IUCN maintains a list of "possibly extinct" and "possibly extinct in the wild" species, modelled on categories used by BirdLife International to categorize these taxa.

Criteria

To be defined as Critically Endangered in the Red List, a species must meet any of the following criteria (A–E) ("3G/10Y" signifies three generations or ten years—whichever is longer—over a maximum of 100 years; "MI" signifies Mature Individuals):

A: Population Size Reduction

1. The rate of reduction is measured either over a 10 year span or across three different generations within that species.
2. The cause for this decline must also be known.
3. If the reasons for population reduction no longer occur and can be reversed, the population needs to have been reduced by at least 90%
4. If not, then the population needs to have been reduced by at least 80%

B: Reduction Across a Geographic Range

1. This reduction must occur over less than 100 km OR the area of occupancy is less than 10 km.
   1. Severe habitat fragmentation or existing at just one location
   2. Decline in extent of occurrence, area of occupancy, area/extent/quality of habitat, number of locations/subpopulations, or amount of MI.
   3. Extreme fluctuations in extent of occurrence, area of occupancy, number of locations/subpopulations, or amount of MI.

C: Population Decline

1. The population must decline to less than 250 MI and either:
   1. A decline of 25% over 3G/10Y
   2. Extreme fluctuations, or over 90% of MI in a single subpopulation, or no more than 50 MI in any one subpopulation.

D: Population Size Reduction

1. The population size must be reduced to numbers of less than 50 MI.

E: Probability of Extinction

1. There must be at least a 50% probability of going extinct in the wild within over 3G/10Y

Causes

The current extinction crisis is witnessing extinction rates that are occurring at a faster rate than that of the natural extinction rate. It has largely been credited towards human impacts on climate change and the loss of biodiversity. This is along with natural forces that may create stress on the species or cause an animal population to become extinct.

Currently the biggest reason for species extinction is human interaction resulting in habitat loss. Species rely on their habitat for the resources needed for their survival. If the habitat becomes destroyed, the population will see a decline in their numbers. Activities that cause loss of habitat include pollution, urbanization, and agriculture. Another reason for plants and animals to become endangered is due to the introduction of invasive species. Invasive species invade and exploit a new habitat for its natural resources as a method to outcompete the native organisms, eventually taking over the habitat. This can lead to either the native species' extinction or causing them to become endangered, which also eventually causes extinction. Plants and animals may also go extinct due to disease. The introduction of a disease into a new habitat can cause it to spread amongst the native species. Due to their lack of familiarity with the disease or little resistance, the native species can die off.

References

1. "IUCN RED LIST CATEGORIES AND CRITERIA" (PDF). 2000-02-09. Retrieved 2018-02-06.
2. "IUCN Red List of Threatened Species". IUCN. Retrieved January 19, 2024.
3. "What is The IUCN Red List?". IUCN Red List. Retrieved August 13, 2020.
4. "Endangered Species". National Geographic. March 17, 2011. Retrieved August 13, 2020.
5. "Summary Statistics". www.iucnredlist.org. Retrieved 2017-12-10.
6. IUCN (February 2014). "Guidelines for Using the IUCN Red List Categories and Criteria" (PDF). Archived from the original (PDF) on 2 May 2015. Retrieved 10 December 2018.
7. Chandler, David (November 22, 2019). "What Are the Causes of Animals Becoming Endangered?". Sciencing. Retrieved August 20, 2020.
8. "What Causes Extinction". American Museum of Natural History. Retrieved October 7, 2022.

v t e Threatened species
Template: Threatened species by region
IUCN Red List	Categories Extinct Extinct (EX) Extinct in the Wild (EW) Threatened Critically Endangered (CR) Endangered (EN) Vulnerable (VU) Lower risk Near Threatened (NT) Least Concern (LC) Lower Risk (LR) Conservation Dependent (LR/cd) Not fully assessed Data Deficient (DD) Not Evaluated (NE) Species Lists Extinct Extinct in the Wild Critically Endangered Endangered Vulnerable Near Threatened Least Concern Data Deficient WP categories Extinct Extinct in the Wild Critically Endangered Endangered Vulnerable Near Threatened Least Concern Data Deficient CITES Appendix I Appendix II Appendix III
By taxa	Threatened arthropods / Endangered arthropods / spiders / Decline in insect populations Decline in amphibian populations Threatened Banksia / rays / sharks / Fungi / Chromista The World's 25 Most Endangered Primates The world's 100 most threatened species
Conservation	Biodiversity action plan Biodiversity threats Conservation biology CITES ARKive Bird conservation Conservation status Conservation-reliant species Ecoregion conservation status Habitat destruction Latent extinction risk Rare species Vulnerability and susceptibility
Pre-2001 categories and subcategories shown in italics.

v t e Threatened species by region
By region	Blue-listed Environmental Vulnerability Index Regional Red List
Australasia	Environment Protection and Biodiversity Conservation Act 1999 ROTAP Threatened Species Protection Act 1995 Threatened ecological community Trade in Endangered Species Act 1989
Canada	Species at Risk Act Committee on the Status of Endangered Wildlife in Canada
Europe	EAZA Ex-situ Programme Funds for Endangered Parrots
South Africa	Endangered Wildlife Trust
United States	Distinct population segment Endangered Species Act of 1973 Endangered Species Act Amendments of 1978 Endangered species recovery plan Endangered Wolf Center National Wildlife Refuge NatureServe conservation status The Nature Conservancy
Lists	Asia List of endangered and protected species of China Endangered mammals of India List of endangered animals in India List of endemic and threatened plants of India List of endangered species in Pakistan List of threatened species of the Philippines List of endangered species in Vietnam Europe Threatened mammals of Europe Endangered plants of Europe Bulgaria Italy Lithuania Russia Ukraine United Kingdom North America List of endangered plants of North America List of endangered animals of North America Endangered mammals and birds of the United States List of threatened mammals of the United States List of threatened birds of the United States List of threatened reptiles and amphibians of the United States Elsewhere Threatened fauna of Australia List of threatened flora of Australia List of endangered flora of Brazil List of threatened mammals of Brazil List of threatened birds of Brazil

• IUCN Red List
• Biota by conservation status