14.This criterion can refer to a decrease in the total area of the community without a contraction in range, a decrease in the range over the whole or part of the area in which the community originally existed, or fragmentation of the community through a decrease in the size of patches. A decrease sufficient to meet the criterion is considered to be a measurable change whereby: the ecological community has contracted to less than some threshold proportion of its former range; or the total area occupied by the community is less than the threshold proportion of its former area; or where less than the threshold proportion of the former area of the community is in patches of a size sufficiently large or well connected with other patches for them to be likely to persist beyond the near future.
Indicative decline thresholds for terrestrial vegetation communities are:
Critically Endangered = a very severe decline 95% or more
Endangered = a severe decline 90% or more
Vulnerable = a substantial decline 70% or more
These thresholds are indicative only; other thresholds might be more appropriate for other kinds of communities (e.g. invertebrate or aquatic communities) or for terrestrial vegetation communities that originally covered a relatively large or a particularly small area.
The application of a specific time frame (such as since 1750) is not considered critical. However, it is important to demonstrate that the ecological community has declined to its present state from some convincingly defined former state.
Where possible, a measurable contraction in distribution should be demonstrated by an appropriate scale of mapping. Where it is not possible to provide precise spatial information on the distribution of an ecological community, particularly at the map scale available (e.g. a very narrow riparian ecosystem), other supporting evidence demonstrating a contraction in distribution may be considered, provided it is supported by independent scientific assessment.
15.Criterion 2. Small geographic distribution coupled with demonstrable threat
The categories under this criterion provide for the listing of ecological communities that have a small geographic distribution and for which a threatening process exists within an understood or predicted time-frame. The general thrust is to recognise that an ecological community with a distribution that is currently small has an inherently higher risk of extinction if it is subject to a threatening process. This criterion is not likely to be considered for an ecological community which has a naturally small distribution but is not currently subject to any threatening process or likely to be subject to such processes in the foreseeable future. It applies only to ecological communities with distributions that are small on a national scale, taking into account all bioregional occurrences regardless of State boundaries.
Indicative thresholds for identifying terrestrial vegetation communities with small distributions are:
Very restricted: Total area of occupancy of < 10 km2 (1,000 ha) or total extent of occurrence < 100 km2 (10,000 ha) or patch sizes of generally < 0.1 km2 (10 ha), depending on the particular community. (Communities tend to have a typical range of patch size that reflects the nature of the habitat and is relevant to their assessment.)
Restricted: Total area of occupancy of <100 km2 (10,000 ha) or total extent of occurrence <1,000 km2 (100,000 ha), or patch sizes of generally < 1 km2 (100 ha), depending on the particular community.
Limited: Total area of occupancy of <1,000 km2 (100,000 ha) or total extent of occurrence <10,000 km2 (1,000,000 ha).
The categories are nested: very restricted is a subset of restricted and limited. The thresholds between categories are indicative only; other thresholds might be more appropriate for particular vegetation communities or communities defined by other attributes.
16.Criterion 3. Loss or decline of functionally important species
17.This criterion refers to native species that are critically important in the processes that sustain or play a major role in the ecological community, and whose removal has the potential to precipitate change in community structure or function sufficient to lead to the community’s eventual extinction (functionally important species). Examples of species that are functionally important in some ecological communities include the dominant seagrass species in a seagrass community or a keystone disperser of fruits, such as the cassowary, in some rainforest communities.
To determine the eligibility of an ecological community under this criterion, there are two linked, inseparable components:
the decline of a population of native species that is likely to play a major role in the community; and
based on that decline, the specified threshold within which restoration of the community is not likely to be possible.
The category for which the ecological community may be eligible for listing under this criterion (Critically Endangered, Endangered or Vulnerable) is dependent on the level of decline of a functionally important species. The community as a whole is only eligible for listing under the appropriate category if it also meets the appropriate timeframe threshold for restoration. If the timeframe threshold is not met, the ecological community is not eligible for listing under any category using this criterion.
In simple terms, this criterion provides timeframes, linked with the severity of decline, in which the decline of the functionally important species must be halted, or reversed, to ensure the continuation of the ecological community.
Basically, if an ecological community had only one key seed disperser, and that key seed disperser was undergoing a very severe decline, then if the species could not be recovered within ten years (the timeframe for critically endangered), the ecological community would be considered critically endangered. If that same key seed disperser was suffering from a substantial decline, instead of a very severe decline, then the species would need to be able to be recovered within 50 years, otherwise it would meet the timeframe for classification as a vulnerable ecological community.
In making an assessment against the criterion, the following steps are followed:
Step 1: determine the level of decline experienced by a population of a functionally important species of that community.
Based on the IUCN species criteria, the TSSC provides the following thresholds as guidance:
very severe decline: an estimated decline of at least 80% over the last 10 years or three generations, whichever is longer;
severe decline: an estimated decline of at least 50% over the last 10 years or three generations, whichever is longer; and
substantial decline: an estimated decline of at least 20% over the last 10 years or three generations, whichever is longer.
Step 2: determine in which category the community may be eligible for listing, according to the level of decline determined in step 1:
Level of decline Category
very severe Critically Endangered
Step 3: predict whether restoration of the community is not likely to be possible within a certain timeframe. Restoration is defined as the near complete or complete recovery of species composition, structure and ecological processes, with or without active intervention.
The timeframe threshold used to determine eligibility depends on the level of decline of the functionally important species:
If the decline is very severe:
the threshold is immediate future- the next 10 years, or three generations of any long-lived species believed to play a major role in sustaining the community, whichever is the longer up to a maximum of 60 years.
If the decline is severe:
the threshold is near future- the next 20 years, or five generations of any long-lived species believed to play a major role in sustaining the community, whichever is the longer up to a maximum of 100 years.
If the decline is substantial:
the threshold is medium-term future- the next 50 years, or ten generations of any long-lived species believed to play a major role in sustaining the community, whichever is the longer up to a maximum of 100 years.
The criterion is met if the time within which restoration of the ecological community is not likely to be possible is longer than the relevant threshold.
In summary, under this criterion a community is eligible for listing:
as Critically Endangered if, for a population of functionally important species there is a very severe decline, to the extent that restoration of the community is not likely to be possible in the immediate future; or
as Endangered if, for a population of functionally important species there is a severe decline, to the extent that restoration of the community is not likely to be possible in the near future; or
as Vulnerable if, for a population of functionally important species there is a substantial decline, to the extent that restoration of the community is not likely to be possible in the medium-term future.
Example 1, to assess an ecological community for which it is known that a functionally important species has declined by 85% over the past 10 years; and restoration of the community is likely to be possible in 100 years:
Step 1: the level of decline is over 80%, which is a very severe decline;
Step 2: based on this decline the community may be eligible for listing as Critically Endangered;
Step 3: based on the decline, the timeframe threshold is immediate future. Since restoration may be possible in 100 years, it is not likely to be possible in the immediate future (10 years), so the community meets the threshold.
The community therefore meets this criterion for listing as Critically Endangered.
Example 2, to assess an ecological community for which it is known that a functionally important species has declined by 53% over the past 10 years; and restoration is likely to be possible in 17 years.
Step 1: the level of decline is at least 50% and less than 80%, which is a severe decline;
Step 2: based on this decline the community may be eligible for listing as Endangered;
Step 3: based on the decline, the timeframe threshold is near future. Since restoration is likely to be possible in 17 years, it does not meet the threshold, as restoration is likely to be possible in the near future (20 years).
The ecological community therefore does not meet this criterion under any category.
18.Criterion 4. Reduction in community integrity
19.This criterion recognises that an ecological community can be threatened with extinction through on-going modifications that do not necessarily lead to total destruction of all elements of the community. Changes in integrity can be measured by comparison with a benchmark state that reflects, as closely as possible, the natural condition of the community with respect to the composition and arrangement of its abiotic and biotic elements and the processes that sustain them.
The following guidelines apply to particular risk categories:
Critically Endangered = change in integrity such that regeneration is unlikely within the immediate future, even with positive human intervention
Endangered = change in integrity such that regeneration is unlikely within the near future, even with positive human intervention
Vulnerable = change in integrity such that regeneration is unlikely within the medium-term future, even with positive human intervention
[Where regeneration is defined as the re-establishment of ecological processes, species composition and community structure within the range of variability exhibited by the original community; and indicative time frames associated with extinction risk are as discussed on page 4.]
The first part of this criterion is intended to capture detrimental changes in the identity and number of component species, the relative and absolute abundances of those species and the state of the abiotic environment that supports them. It includes irretrievable loss of native species and invasion by non-native species, as well as changes in the physical environment sufficient to lead to ongoing change in biota.
It may be helpful to assess the level of degradation using non-biological factors known to support the community and the species most significant in its description. For example, if the species of invertebrates that characterise a cave community have no mechanism to survive desiccation, the complete drying out of the cave could be considered sufficient to cause the extinction of that community.
The second part of this criterion recognises that ecological processes are important to maintain an ecological community (e.g. fire regimes or flooding) and that disruption to those processes can lead to the decline in integrity of the ecological community. This criterion could apply where disruption of processes is evident or imminent (e.g. altered hydrology leading to rising water tables and/or dryland salinity) prior to a measurable decline in integrity of the ecological community. It could also apply where recruitment to the community is known to be disrupted but where long lived species mask immediate community breakdown (e.g. when seedlings of a dominant tree species are not able to persist in the face of grazing by exotic herbivores). Such a criterion allows for recognition of a problem at an early stage.
20.Criterion 5. Rate of continuing detrimental change
A continuing change refers to a recent, current or projected future change whose causes are either not known or not adequately controlled, and so is liable to continue unless remedial measures are taken. Natural fluctuations will not normally count as a continuing change, but an observed change should not be considered to be part of a natural fluctuation unless there is evidence for this.
This criterion has been divided into an expression of change with two alternative expressions of the indication of that change. In doing this, the TSSC has recognised that the rate of continuing detrimental change occurring in a community is relevant to its risk of extinction independently of any pre-European data. It is difficult to quantify because detrimental change can be manifest in many different ways and adequate data for monitoring change may not be available. The TSSC will have to exercise “ecological judgement” in applying these criteria, nominations should therefore provide as much evidence as possible of the factors affecting decline and how these factors act on the community.
The following rates drawn from the updated IUCN Red List Criteria for species are intended to provide guidance only:
Critically Endangered an observed, estimated, inferred or suspected detrimental change of at least 80% over the immediate past or projected for the immediate future
Endangered an observed, estimated, inferred or suspected detrimental change of at least 50% over the immediate past or projected for the immediate future
Vulnerable an observed, estimated, inferred or suspected detrimental change of at least 30% over the immediate past or projected for the immediate future
Where detrimental change may refer to any one of the components of this criterion, i.e. to (a) geographic distribution or populations of critically important species, or (b) degradation or disruption of important processes.
Data to demonstrate this criterion must be documented. They can be in the form of direct measurements of any of the components, actual or potential levels of exploitation, or the known effects of introduced biotic or abiotic elements on any of the components.
21.Criterion 6. Quantitative analysis showing probability of extinction
This criterion is intended to include any form of analysis that estimates the extinction probability of an ecological community based on known characteristics of important species or other components, habitat requirements, ecological processes, threats and any specified management options. The TSSC has recognised that this is an emerging area of science and will examine any acceptable modelling that may be provided to it. The Committee will use peer review as part of its process for this criterion.
Population Viability Analysis (PVA) is an example of such a technique appropriate for species, but no formal equivalent has been developed for ecological communities. Regardless of their form, quantitative analyses should make full use of all relevant available data. In a situation in which there is limited information, such data as are available can be used to provide an estimate of extinction risk (for example, estimating the impact of stochastic events on habitat). In presenting the results of quantitative analyses, the assumptions (which must be explicitly stated) and the data used must be documented.
22.Part E – Area of occupancy and extent of occurrence
Extent of occurrence
Extent of occurrence is defined as the area contained within the shortest continuous imaginary boundary which can be drawn to encompass all the known, inferred or projected sites of present occurrence of a taxon/ecological community, excluding cases of vagrancy (see Figure 1). This measure may exclude discontinuities or disjunctions within the overall distributions of taxa/ecological communities (e.g. large areas of obviously unsuitable habitat, see 'area of occupancy' below). Extent of occurrence can often be measured by a minimum convex polygon (the smallest polygon in which no internal angle exceeds 180 degrees and which contains all the sites of occurrence).
Area of occupancy
Area of occupancy is defined as the area within its 'extent of occurrence' (see above) which is occupied by a taxon/ecological community, excluding cases of vagrancy. The measure reflects the fact that a taxon/ecological community will not usually occur throughout the area of its extent of occurrence, which may contain unsuitable or unoccupied habitats. In some cases (e.g. irreplaceable colonial nesting sites, crucial feeding sites for migratory taxa) the area of occupancy is the smallest area essential at any stage to the survival of existing populations of a taxon/ecological community. The size of the area of occupancy will be a function of the scale at which it is measured, and should be at a scale appropriate to relevant biological aspects of the taxon/ecological community, the nature of threats and the available data. To avoid inconsistencies and bias in assessments caused by estimating area of occupancy at different scales, it may be necessary to standardize estimates by applying a scale-correction factor. It is difficult to give strict guidance on how standardization should be done because different types of taxa/ecological communities have different scale-area relationships.
Figure 1. Two examples of the distinction between extent of occurrence and area of occupancy. (A) is the spatial distribution of known, inferred or projected sites of present occurrence. (B) shows one possible boundary to the extent of occurrence, which is the measured area within this boundary. (C) shows one measure of area of occupancy which can be achieved by the sum of the occupied grid squares.
Form current as of November 2010