RLE Categories & Criteria

Based on the hypothesis that ecosystem risk is a function of the species that compose them, their interactions, and the ecological processes they depend on, the IUCN Red List of Ecosystems protocol includes five criteria for assessing the risk of ecosystem collapse:

• A) Reduction in geographic distribution,
• B) Restricted geographic distribution,
• C) Environmental degradation,
• D) Disruption of biotic processes or interactions and
• E) Quantitative analysis that estimates the probability of ecosystem collapse.

There are eight possible categories of risk for each ecosystem. Three of them are assigned based on quantitative thresholds: Critically Endangered (CR), Endangered (EN), and Vulnerable (VU) - together, these categories are described as under threat. These categories are nested, so that an ecosystem type meeting a criterion for Critically Endangered will also meet the criteria for Endangered and Vulnerable.

There are four additional qualitative categories that accommodate:

1. ecosystems that fail to meet the quantitative criteria for the threatened ecosystem categories (NT, Near Threatened);
2. ecosystems that unambiguously meet none of the quantitative criteria (LC, Least Concern);
3. ecosystems for which too few data exist to apply any criterion (DD, Data Deficient); and
4. ecosystems that have not yet been assessed (NE, Not Evaluated).

An additional category (CO, Collapse) is assigned to ecosystems that have collapsed throughout their distribution, the analogue of the extinct (EX) category, used for species by IUCN (2016).