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Ecosystem Name

Summary

Summary of the case study. Use no more than 400 words.

Classification

Ecosystems may be grouped into four general realms: terrestrial, subterranean, freshwater and marine. Authougth no universal ecosystem taxonomy exists, a range of classifications have been developed. In this section please indicate an equivalence to IUCN ecosystem types and you can include more equivalences to different international ecosystem classifications if you like.

Ecosystem Description

Until a universal ecosystem taxonomy exists, risk assessment of each ecosystem will need to incorporate a description of its characteristic biota, abiotic features and ecological processes that are relevant to risk assessment. In this context, the concept of 'characteristic native biota' is a subset of all native biodiversity that may be described using taxonomic traits and/or functional traits (e.g. guild composition, dispersal spectra, key interacting components, etc.). This subset consists of biodiversity components that play a role in ecosystem function and/or distinguish an ecosystem from others. It includes biota that drive ecosystem dynamics as ecosystem engineers, trophic or structural dominants and functionally unique elements, as well as diagnostic elements. Characteristic biota therefore excludes uncommon or vagrant species that contribute little to function and may be more common in other ecosystems. Description will usually not require extensive inventories of species compositions, interaction networks or fluxes of matter and energy, but should articulate the salient features that define the identity of an ecosystem, distinguish it from the others, and provide a baseline for assessing change.

Distribution

Specify the geographic occurrence or range of the ecosytem at local, regional or global level.

Threatening processes

Transitions to collapse may be gradual, sudden, linear, non-linear, deterministic or highly stochastic. The dominant dynamic in an ecosystem will depend on abiotic or external influences (e.g. weather patterns or human disturbance) internal biotic processes (e.g. competition, predation, pathogen epidemics), and historical legacies and spatial context. An ecosystem may thus be driven to collapse by any of several different threatening processes. These threats should produce recognizable symptoms that an ecosystem is at risk of collapse including changes in spatial distribution, the physical environment, the biota itself, and interactions among organisms and their environment. A mechanistic understanding of ecosystem dynamics is a prerequisite for diagnosing changes that are detrimental to biota and distinguishing them from other kinds of change.

Assessment

You could use any version of the IUCN Red List Criteria for Threatened Ecosystems, but you need to specify which version of categories you are using. Assessment of any ecosystem should evaluate as many criteria as possible. Overall status will be the highest level of risk returned by any of the criteria. This approach exploits the ensemble properties of the criteria, which represent alternative mechanisms of potential collapse (in previous versions as elimination or extinction), and minimizes the impact of missing data that may preclude assessment of any one criterion. The rule set structure also avoids assumptions that different symptoms are additive or interchangeable in their effect on overall risk of ecosystem collapse, but may underestimate risk if data on the most limiting criteria are lacking or if there are synergistic interactions between different mechanisms (Burgman and others 1999).

Risk assessment should be based on the best available data. These will often be uncertain, fragmentary and more limited as the thematic resolution of assessment units increases. Various methods of estimation, scaling up and inference can be deployed to assess risk status within bounds of uncertainty, but when any category is plausible an ecosystem should be designated Data Deficient until available data permit assessment of at least one criterion (for more information see Key Documents).

References

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Figures or photos

Additional Files


Definitions of terms

Area of OccupancyArea of occupancy is defined as the area within its ‘extent of occurrence’ (see below), which is occupied by an ecosystem (cf. IUCN 2011). The measure reflects the fact that an ecosystem will not usually occur throughout its extent of occurrence, which may contain unsuitable or unoccupied areas. The size of the area of occupancy will be a function of the scale at which it is measured. For assessment using the criteria in Table 3 (Keith et al. 2013), it must be estimated by counting the number of occupied 10 × 10 km grid cells (cf. IUCN 2011), excluding those in which the area of the ecosystem accounts for less than 1% (i.e. 1 km²) of the cell area.

Characteristic native biotaGenes, populations, species, assemblages of species and their key interactions that distinguish the ecosystem compositionally from others. It also includes biota that drive ecosystem dynamics, for example as ecosystem engineers, trophic or structural dominants, or functionally unique elements (Keith et al. 2013(suppl.)), even though they may be common in other ecosystems. Characteristic biota may be defined in terms of functional traits (e.g. guild composition, dispersal spectra, key interacting components, etc.) as well as taxonomic traits. Characteristic biota excludes uncommon or vagrant species that contribute little to its function and may be more common in other ecosystems.

CollapseA theoretical threshold, beyond which an ecosystem no longer sustains most of its characteristic native biota or no longer sustains the abundance of biota that have a key role in ecosystem organisation (e.g. trophic or structural dominants, unique functional groups, ecosystem engineers, etc.). Collapse has occurred when all occurrences of an ecosystem have moved outside the natural range of spatial and temporal variability in composition, structure and function. Some or many of the pre-collapse elements of the system may remain within a collapsed ecosystem, but their relative abundances may differ and they may be organised and interact in different ways with a new set of operating rules. Ecosystem collapse may be viewed as the analogue of functional extinction in species, which precedes or at least coincides with complete elimination of all characteristic biota.

Continuing declineA in decline distribution, environmental degradation or disruption of biotic interactions that must i) reduce the ability of an ecosystem to sustain its characteristic native; ii) be non-trivial in magnitude; iii) be likely to continue into the future. Continuing declines may occur gradually or episodically through time. They exclude trivial trends that are unlikely to be associated with declines in characteristic native biota within the ecosystem.

Disruption of biotic interactionsA change in interactions among different groups of biota, or between the biota and the physical environment, which reduces the capacity of the ecosystem to sustain its characteristic native biota (i.e. biotic degradation cf. environmental degradation). Interactions may be between biota within an ecosystem, with biota of another ecosystem or between biota and environmental factors. Assessment of disruption to biotic interactions under criterion D involves the following steps:

      1. Selection of a suitable biotic variable or variables, with justification of its relationship(s) to salient processes of ecosystem dynamics (e.g. with reference to a process model specific to the ecosystem under evaluation).
      2. Estimate the value of the variable across the distribution of the ecosystem at the end of the assessment period (present day for D1 & D3, 50 yrs in future for D2).
      3. Estimate how much the biotic variable changed since the beginning of the assessment period (50 yrs ago for D1, present day for D2, 1750 for D3). Generally, patches of the ecosystem that may have been destroyed (e.g. by land conversion) should be excluded from this estimate.
      4. Calculate the absolute % change in the biotic variable over the assessment period (this may require temporal interpolation or extrapolation and justification of associated assumptions).
      5. Range-standardise the estimated of absolute % change using a collapse threshold estimated specifically for the ecosystem to obtain an estimate of relative severity of degradation.
      6. Estimate the extent (as % of the ecosystem distribution) over which the change has occurred.
      7. Compare the estimates of relative severity and extent to the assessment thresholds under criterion D (Table 3 (Keith et al. 2013)).

DistributionThe spatial occurrence of an ecosystem. For criterion A, changes in distribution should be estimated with the best available mapping of an appropriate surrogate for the ecosystem (e.g. remote sensing of terrestrial vegetation, marine reefs, etc.). For criterion B, distribution size must be estimated using the standard metrics – see definitions of Area of Occupancy (AOO), Extent of Occurrence (EOO), Locations.

EcosystemComplexes of organisms and their associated physical environment, within an area (after Tansley 1935, cited by Keith et al. 2013). They have four essential elements: a biotic complex; an abiotic environment or complex; the interactions within and between them; and a physical space in which these operate (Pickett & Cadenasso 2002).

Environmental degradationA change in the abiotic features of an ecosystem that reduce its capacity to sustain its characteristic native biota. Assessment of environmental degradation under criterion C involves the following steps:

      1. Selection of a suitable environmental variable or variables, with justification of its relationship(s) to salient processes of ecosystem dynamics (e.g. with reference to a process model specific to the ecosystem under evaluation).
      2. Estimate the value of the variable across the distribution of the ecosystem at the end of the assessment period (present day for C1 & C3, 50 yrs in future for C2).
      3. Estimate how much the degradation variable changed since the beginning of the assessment period (50 yrs ago for C1, present day for C2, 1750 for C3). Generally, patches of the ecosystem that may have been destroyed (e.g. by land conversion) should be excluded from this estimate.
      4. Calculate the absolute % change in the degradation variable over the assessment period (this may require temporal interpolation or extrapolation and justification of associated assumptions).
      5. Range-standardise the estimated of absolute % change using a collapse threshold estimated specifically for the ecosystem to obtain an estimate of relative severity of degradation.
      6. Estimate the extent (as % of the ecosystem distribution) over which the degradation has occurred.

EstimatedInformation that is based on calculations that may include statistical assumptions about sampling, or biological assumptions about the relationship between an observed variable (e.g. an index of abundance of a key species) to the variable of interest (e.g. biotic interactions) (cf. IUCN 2011). These assumptions should be stated and justified in the documentation supporting and assessment. Estimation may also involve interpolation in time to calculate the variable of interest for a particular time step (e.g., a 50-year reduction in distribution based on observations or estimations of distribution 40 and 60 years ago).

Extent of OccurrenceExtent of occurrence is 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 an ecosystem (cf. IUCN 2001). For assessment using the criteria (Table 3 (Keith et al. 2013)), it must be estimated using a minimum convex polygon (the smallest polygon in which no internal angle exceeds 180 degrees and which contains all the sites of occurrence).

InferredInformation that is based on indirect evidence, on variables that are indirectly related to the variable of interest, but in the same general type of units (IUCN 2011). Inferred values rely on more assumptions than estimated values. For example, inferring disruption of biotic interactions from catch statistics not only requires statistical assumptions (e.g., random sampling) and biological assumptions (about the relationship of the harvested section of the population to the total population), but also assumptions about trends in effort, efficiency, and spatial and temporal distribution of the harvest in relation to the population. Inference may also involve extrapolating an observed or estimated quantity from known ecosystem occurrences to calculate the same quantity for other occurrences. Whether there are enough data to make such an inference will depend on how large the known occurrences are as a proportion of the whole distribution, and the applicability of the threats and trends observed in the known occurrences to the rest of the ecosystem. The method of extrapolating to unknown occurrences depends on the criteria and on the type of data available for the known occurrences.

LocationA geographically or ecologically distinct area in which a single threatening event can rapidly affect the ecosystem (cf. IUCN 2001). The size of the location depends on the area covered by the threatening event and may include part of one or many separate patches of the ecosystem. Where an ecosystem is affected by more than one threatening event, location should be defined by considering the most serious plausible threat.

Observed Information that is directly based on well-documented observations of all known occurrences of the ecosystem (cf. IUCN 2011).

ProjectedSame as “estimated”, but the variable of interest is extrapolated in time towards the future (IUCN 2011). Projected variables require a discussion of the method of extrapolation (e.g. justification of the statistical assumptions or the ecosystem model used) as well as the extrapolation of current or potential threats into the future, including their rates of change.

Relative severityThe magnitude of a decline in ecosystem function (criteria C and D) expressed as a percentage change in a relevant biotic or abiotic variable relative to a decline that would be large enough to exceed an ecosystem-specific threshold of collapse (see Fig. 6 in Keith et al. 2013).

ThreatA tractable agent, mechanism or process that causes either a continuing decline in distribution, continuing environmental degradation or continuing disruption of biotic interactions or a future decline in those factors that is likely to occur in the near future (i.e. within 20 years).