Conservation statuses explained

The International Union for Conservation of Nature (IUCN) is an authority that evaluates the conservation status of species around the globe.

They use a system of nine categories, ranging from “Least Concern” to “Extinct,” to categorize the severity of the threat facing a specific species.

These categories are based on factors such as population size, habitat loss, and hunting or poaching. The categories act as an alert mechanism for extinction risk, allowing conservationists and decision-makers to prioritize species protection with limited resources.

  1. Extinct (EX): 

    A species that no longer exists. The species no longer found anywhere in the world are included in this category.

    When a species is labeled as Extinct, it means that the last individual of that species died. Sometimes, it is not clear if a species is extinct, so the term Presumed Extinct is used if extensive surveys in the known and probable habitat across its historic range have failed to record an individual. 

  2. Extinct in the Wild (EW):

    A species is said to be Extinct in the wild, which indicates a species no longer exists in its natural habitat but might survive in captivity or via conservation efforts. It can only be found in captivity or small populations now – outside/far away from where it used to live, while the species has not been recorded in the wild for at least 50 years, and extensive surveys in known and/or expected habitats have failed to locate any individuals.

    Additionally, if a species requires intensive individual-level management and intervention to survive, it will be classified as EW. This typically applies to species on the brink of extinction and needing considerable conservation efforts.

  3. Critically Endangered (CR): 

    A species that faces an extremely high risk of extinction in the wild. The following factors can be used to determine whether a species is critically endangered: 

    • Population size reduction, geographic range shrinkage, population decline, population decrease to less than 50 mature individuals and at least a 50% probability of extinction in the wild within ten years or three generations.
    • A decline of at least 80% in population size over the last 10 years or three generations, whichever is longer, based on direct observation
    • An area of occupancy (AOO) of less than 10 square kilometers is severely fragmented or known to exist at only one location.
    • A population size estimated to number fewer than 250 mature individuals.
    • A continuing decline observed or projected, in any of the following: a. population size, b. AOO, c. extent of occurrence (EOO), d. area, extent, or quality of habitat, e. number of locations or subpopulations, f. the number of mature individuals
    • Extreme fluctuations in any of the above-mentioned factors, which are expected to continue or occur in the future.

  4. Endangered (EN): 

    A species that is very likely to become extinct in their known native ranges in the near future. Species classified as endangered have a higher risk of extinction than those classified as vulnerable.

    To qualify as EN, a species must meet one of the following criteria:

    • A decline of at least 50% in population size over the last 10 years or three generations, whichever is longer, based on direct observation or indirect evidence 
    • A population size reduction of at least 50%, projected or suspected to be met within the next 10 years or three generations, whichever is longer.
    • An actual population size of fewer than 2,500 mature individuals and a continuing decline of at least 20% over the last 5 years or two generations, whichever is longer; or a population of fewer than 2,500 mature individuals with a probability of at least 20% of going extinct within the next 20 years or five generations, whichever is longer, based on a high-risks associated or habitat fragmentation.

  5. Vulnerable (VU): 

    A species that faces significant threats to its survival. Species that are listed as vulnerable are not as highly risk as those in the endangered or critically endangered categories. However, they are still at significant risk of extinction and require conservation efforts to prevent further decline.

    Species can be classified as vulnerable if they meet any of the following criteria:

    • Their population has declined by at least 30% over the last 10 years or three generations (whichever is longer).
    • Their geographic range is very restricted (typically less than 20,000 km²).
    • They have a small population size, usually fewer than 10,000 mature individuals.
    • Their population is fragmented or experiencing significant fluctuations.
    • They are threatened by habitat loss, hunting, or other threats.

  6. Near Threatened (NT):

    A species close to being classified as Vulnerable but does not quite meet the criteria is put in this category.

    Near Threatened does not have specific criteria. It is used for species that are close to meeting the criteria for the Vulnerable category, like:

    • A decline in population size, range, or habitat that has not yet caused the species to qualify for Vulnerable status but is expected to do so in the near future.
    • The species has a small population size or a restricted range that is not severely fragmented, but it is not currently in decline.
    •  A quantitative analysis shows that the probability of extinction in the wild is at least 10% within 100 years or three generations, whichever is longer.

  7. Least Concern (LC): 

    A widespread and numerous species in the wild, it poses a low danger of extinction and has the lowest level of conservation concern among the IUCN’s categories. This represents that the species’ population is steady or growing, and the species has a large distribution range with no severe threats to its survival.

    However, being assigned to the LC category does not mean a species is completely out of danger. Many species from LC face localized threats, such as habitat loss and degradation, hunting, and climate change, which could eventually push them to higher conservation categories.

  8. Data Deficient (DD): 

    A species for which there is insufficient information to assess its risk of extinction. This means insufficient scientific data is available to evaluate their conservation status.

    This does not suggest that a species is not threatened, but rather that more information is required to accurately analyze its conservation status. According to IUCN recommendations, the Data Deficient category should only be given as a last resort because it increases the risk that these species would be neglected for immediate conservation efforts.

    Interestingly, some conservationists have criticized the DD category for being too general. However, it is still a helpful tool in finding species that may need attention and for promoting additional study and data collection. As a result, DD species are frequently the topic of continuous study and research.

  9. Not Evaluated (NE): 

    A species that has not yet been evaluated for its risk of extinction due to a lack of data. It simply means that there is not enough knowledge about these species to determine whether they are at risk of extinction or not. The NE category also includes newly discovered species; as scientists continue to explore and discover new species, many of them are added to the NE category until sufficient data is collected to evaluate their status. 

    The world’s most elusive and rare species are often in the Not Evaluated (NE) category. Many of these species live in remote and inaccessible areas, making it difficult to gather information on their population size, distribution, and threats they face.

 A species is classified as DD when there is some knowledge about it but not enough to provide a valid evaluation of its conservation status. A species, on the other hand, is classed as NE when there is simply insufficient information available to make any evaluation or analysis.

This category highlights the need for more research and monitoring of these species to better understand biology, ecology, and threats they face.

IUCN 5 criterias

Criterion A: Reduction in population size:

a. If a species has declined a lot in the last 10 years or three generations, whichever is longer 
is expected to decline by at least 10% in the next 10 years or three generations, whichever is longer:  Critically Endangered (CR), Endangered (EN), Vulnerable (VU)

b. Population reduction projected or suspected to be ≥10% over the next 10 years or three generations, whichever is longer: Near Threatened (NT)

Criterion B: Restricted geographic range:

a. Extent of occurrence (EOO) <5,000 km², and the area of occupancy (AOO) <500 km²: CR, EN

b. EOO <20,000 km² and AOO <2,000 km²: VU

c. EOO <20,000 km² or AOO <2,000 km², but not both: NT

Criterion C: Small population size and decline:

a. Population size: <250 mature individuals: CR

b. Population size: <2,500 mature individuals: EN

c. Population size: <10,000 mature individuals: VU

Criterion D: Very small population size or restricted distribution:

a. Population size: <50 mature individuals: CR

b. Population size: <250 mature individuals: EN

c. Population size: <1,000 mature individuals: VU

Criterion E: Quantitative analysis:

a. Quantitative analysis indicates a probability of extinction in the wild of at least 50% within 10 years or three generations, whichever is longer: CR

b. Quantitative analysis indicates a probability of extinction in the wild of at least 20% within 20 years or five generations, whichever is longer: EN

c. Quantitative analysis indicates a probability of extinction in the wild of at least 10% within 100 years: VU

Regional conservation status

The IUCN categories are based on global species assessments, but these categories may differ when applied at regional or national levels. This is because the IUCN criteria consider a species’ entire range and a species may face different threats and have different population trends in different parts of its range. 

For example:

A species may be categorized as Least Concern globally, but it could still be at risk in a specific region due to factors such as small population size or declining numbers, or poaching threats. In contrast, a species categorized as Vulnerable (VU) globally may not be at risk in a particular region (LC) where its population is stable. This means that these categories may not always be the same at different geographic scales.

Also, These categories are based on specific criteria that are applied to individual species, taking into account factors like population size, range, and decline. Therefore, two species with the same population can receive different categories based on their unique circumstances. 

For example:

Two species may have the same population size, but one of them is Critically Endangered (CR) due to its endemic nature and restricted range, along with high levels of poaching threats throughout its range. The other species, with a larger range area across two continents and fewer threats, may be classified as Least Concern (LC).