Not Evaluated (NE) Species and the IUCN Red List
In the global effort to track biodiversity and prevent extinction, the International Union for Conservation of Nature (IUCN) maintains the Red List of Threatened Species. While many people are familiar with terms like "Endangered" or "Critically Endangered," there is a significant category known as Not Evaluated (NE). This designation serves as a critical marker for species that have not yet undergone a formal assessment to determine their risk of extinction.
A species is classified as Not Evaluated if it has been explicitly categorized as such by the IUCN or if it is entirely absent from the IUCN repository. Essentially, if a species has not been reviewed by the organization, it falls into this category by default.
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The Spectrum of Extinction Risk
The IUCN utilizes nine different threat assessment categories to quantify the risk of global extinction. These categories generally exist on a spectrum, ranging from Extinct (EX) at the most severe end to Least Concern (LC) for those with minimal risk.
However, two categories sit outside this linear spectrum: Data Deficient (DD) and Not Evaluated (NE). These are not placed on the risk scale because they do not describe the level of threat, but rather the state of the available research. They indicate that there is insufficient information or a lack of review to assign the species to a specific risk category.
Understanding the Implications of NE Status
It is a common misconception that a Not Evaluated status implies a species is safe. In reality, the NE label does not mean a species is non-threatened; it simply means that the risk has not yet been quantified or published through a formal study.
Because of this uncertainty, the IUCN advises that NE species should not be treated as if they are safe from extinction. Instead, the organization suggests that it may be appropriate to give these species the same level of attention as threatened taxa until a formal assessment can be completed.
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Scale and Scope of the NE Category
The sheer volume of species on Earth makes the task of evaluation monumental. By 2015, the IUCN had assessed over 76,000 species, identifying approximately 24,000 as globally threatened. Despite these efforts, the Not Evaluated category remains the largest of all nine categories.
This is due to the vast gap between assessed species and the estimated number of species existing on Earth, which varies widely between 3 million and 30 million. Consequently, the majority of the world's biodiversity remains in the NE category.
Beyond Species: Regional and Ecosystem Applications
The framework established by the IUCN is not limited to global species lists. The assessment and categorization process has been adapted for use at regional and national levels, allowing countries to establish their own Red Data lists to manage local conservation threats.
Furthermore, these criteria are now being applied to ecosystems. In this context, every ecosystem is automatically classified as Not Evaluated before the formal assessment process begins.
Key Facts
- Definition: Not Evaluated (NE) refers to species not yet assessed by the IUCN or those missing from the IUCN repository.
- Position: NE is one of nine categories but sits outside the extinction risk spectrum.
- Precaution: The IUCN warns that NE species should not be assumed to be non-threatened.
- Scale: NE is the largest of all IUCN categories due to the millions of species yet to be studied.
- Versatility: The NE designation is also used for ecosystems prior to their assessment.
| Category | Meaning | Position on Risk Spectrum |
|---|---|---|
| Extinct (EX) | No known individuals remaining | Highest Risk |
| Least Concern (LC) | Lowest risk of extinction | Lowest Risk |
| Data Deficient (DD) | Insufficient information to assess | Outside Spectrum |
| Not Evaluated (NE) | Not yet reviewed or not in repository | Outside Spectrum |
Frequently Asked Questions
Does Not Evaluated mean the species is safe?
No. A Not Evaluated status simply means the species has not been studied enough to quantify its risk. It should not be treated as non-threatened.
How does Not Evaluated differ from Data Deficient?
While both are outside the risk spectrum, Not Evaluated refers to species that have not been reviewed at all or are missing from the repository, whereas Data Deficient refers to species that have been reviewed but lack sufficient data to be categorized.
How many species have been assessed by the IUCN?
As of 2015, the IUCN had assessed over 76,000 species, with about 24,000 of those categorized as globally threatened.
Can the NE category be applied to things other than species?
Yes, the IUCN assessment criteria are also applied to ecosystems, all of which are categorized as Not Evaluated before their assessment process begins.
Why is the NE category the largest of all IUCN categories?
It is the largest because the number of species on Earth is estimated to be between 3 million and 30 million, far exceeding the number of species that scientists have had the resources to evaluate.