Table 1.
Possible categories and criteria for use in developing a red list of ecosystemsa.
| Criterion | Subcriterion | Statusb |
|---|---|---|
| A: Short-term decline (in distribution or ecological function) on the basis of any subcriterion | 1. observed, estimated, inferred or suspected decline in distribution of | |
| ≥80%, | CR | |
| ≥50%, or | EN | |
| ≥30% | VU | |
| over the last 50 years | ||
| 2. projected or suspected decline in distribution of | ||
| ≥80%, | CR | |
| ≥50%, or | EN | |
| ≥30% | VU | |
| within the next 50 years | ||
| 3. observed, estimated, inferred, projected, or suspected decline in distribution of | ||
| ≥80%, | CR | |
| ≥50%, or | EN | |
| ≥30% | VU | |
| over any 50-year period, where the period must include both the past and the future | ||
| 4. relative to a reference state appropriate to the ecosystem, a reduction or likely reduction of ecological function that is | ||
| (a) very severe, in at least one major ecological process, throughout ≥80% of its extant distribution within the last or next 50 years; | CR | |
| (b1) very severe, throughout ≥50% of its distribution within the last or next 50 years; | EN | |
| (b2) severe, in at least one major ecological process, throughout ≥80% of its distribution within the last or next 50 years; | EN | |
| (c1) very severe, in at least one major ecological process, throughout ≥30% of its distribution within the last or next 50 years; | VU | |
| (c2) severe, in at least one major ecological process, throughout ≥50% of its distribution within the last or next 50 years. | VU | |
| (c3) moderately severe, in at least one major ecological process, throughout ≥80% of its distribution within the last or next 50 years | VU | |
| B: Historical decline (in distribution or ecological function) on the basis of either subcriterion 1 or 2 | 1. estimated, inferred, or suspected decline in distribution of | |
| ≥90%, | CR | |
| ≥70%, or | EN | |
| ≥50% | VU | |
| in the last 500 years | ||
| 2. relative to a reference state appropriate to the ecosystem, a very severe reduction in at least one major ecological function over | ||
| ≥90%, | CR | |
| ≥70%, or | EN | |
| ≥50% of its distribution in the last 500 years | VU | |
| C: Small current distribution and decline (in distribution or ecological function) or very few locations on the basis of either subcriterion 1 or 2 | 1. extent of occurrencec estimated to be | |
| ≤100 km2, | CR | |
| ≤5,000 km2, or | EN | |
| ≤20,000 km2 | VU | |
| and at least one of the following: | ||
| (a) observed, estimated, inferred, or suspected continuing decline in distribution, | ||
| (b) observed, estimated, inferred, or suspected severe reduction in at least one major ecological process, | ||
| (c) ecosystem exists at only one location, 5 or fewer locations, or 10 or fewer locations. | ||
| CR | ||
| EN | ||
| VU | ||
| or | ||
| 2. area of occupancyc estimated to be | ||
| ≤10 km2, | CR | |
| ≤500 km2, or | EN | |
| ≤2000 km2 and at least one of the following: | VU | |
| (a) observed, estimated, inferred, or suspected continuing decline in distribution, | ||
| (b) observed, estimated, inferred, or suspected severe reduction in at least one major ecological process, | ||
| (c) ecosystem exists at only one location, 5 or fewer locations, or 10 or fewer locations | ||
| CR | ||
| EN | ||
| VU | ||
| D: Very small current distribution, estimated to be | ≤5 km2, | CR |
| ≤50 km2, or | EN | |
| ≤100 km2, | VU | |
| and serious plausible threats, but not necessarily evidence of past or current decline in area or function. |
a
Based on the IUCN Red List (IUCN 2001) and other systems proposed to date (Nicholson et al. 2009).
b
Abbreviations: CR, critically endangered; EN, endangered; VU, vulnerable.
c
See IUCN (2001, 2010b) for guidelines on measuring extent of occurrence and area of occupancy.
[Correction added after publication 5 November 2010: Errors in the second column of Criterion D were amended.]