6 ToR c Applying risk‐based methodologies to assess degree of impact
6.2 Iterative development of the Robinson et al. (REA) methodology
has been modified twice, and the main developments are described below following a brief summary of the original version. Terminology used in the descriptive text of this section is taken from the defined terms used by the REA approach. It does not necessarily reflect terminology that is widely used or accepted in the ICES commu‐
nity.
6.2.1 REA 2008a
The approach outlined by Robinson et al., 2008a was specifically designed to assess consistently the degree of impact of various pressures on the full range of ecosystem components. The authors state that achieving consistency in assessing degree of im‐
pact would be assured by (1) selecting a threshold for a limited number of state indi‐
cators for each ecosystem component that defined the point beyond which their recovery potential is threatened and using this to interpret current level of resistance to a pressure (low resistance where the sustainability of a component is currently at risk as a result of a specific pressure), and (2) categorizing current resilience based on a range of recovery times that reflected the full potential across all marine ecosystem components. Key pressures would be those that had caused one or more components to be moved beyond their resistance threshold and among those, highest levels of risk would be associated with pressure/component combinations with the longest recov‐
ery times.
6.2.2 REA 2008b
The first version of REA, 2008a was largely a conceptual framework, and further de‐
velopment was required to make the process operational in the context of a large‐
scale integrated ecosystem assessment. For example, Robinson et al., 2008a state that although scientifically derived resistance thresholds could easily be identified for some elements of the ecosystem (e.g., Bpa and BLim for commercial fish), no such thresholds were agreed for most of the listed ecosystem components. The issue of selecting baseline conditions (= a suitable reference period) also required work as the initial concept was based on a comparison of current conditions with a recent refer‐
ence period (i.e., relative to a regular reporting cycle of 6‐10 years), the objective be‐
ing to select the current key pressures on the ecosystem. Other applications (i.e., the OSPAR Quality Status Report) would require an assessment of the key pressures that had affected the current status of ecosystem components relative to former natural conditions. Finally, further work was required to finalize the level of aggregation of ecosystem components and pressures.
o Selecting thresholds2 for ecosystem components
2 Threshold is the term used by the REA methodology, but it is considered by WGECO to be analogous to the term reference point which is more commonly used by the ICES community.
In theory, it should be possible to describe any component in terms of the level of degradation that could occur before its recovery potential begins to diminish. In prac‐
tice it is recognized that for most components, this relationship is not well under‐
stood or documented in terms of any quantitative evidence (see discussions in ICES, 2007 Section 2 and Robinson et al., 2008b Section 2.2). Following consultation with experts on habitats and their species, thresholds were selected for broad habitat com‐
ponents (e.g., intertidal sediment habitats; JNCC, 2008). These were based on state indicators related to range, extent and condition of habitats (where condition covered both biological (benthic invertebrates) and physical structure and function). Thresh‐
olds based on area were selected for each of the three descriptors (range, extent and condition) using elements from the favourable conservation status (FCS; JNCC, 2007) and OSPAR Annex V Texel‐Faial criteria (OSPAR, 2003). It was recognized by the authors that there was no clear scientific rationale behind the thresholds set. Indica‐
tors and thresholds for species group components (e.g., Fish, Seabirds) were less well developed at this stage.
o Baseline conditions and geographic scale
As the thresholds set for each ecosystem state indicator in REA 2008b related to an amount of decline, it was noted that, dependent on the reference period (the baseline) being used, and the geographic extent of the region being assessed, the acceptable amount of decline could vary. Thus thresholds were set specific to the context of in‐
dividual assessments (e.g., they varied dependent on when the baseline was set for).
Definitions were provided for each baseline.
o Level of aggregation of ecosystem components
Ultimately for a broad ecosystem assessment, there will always be a compromise in terms of the level of aggregation of ecosystem components. Having trialled the REA, 2008a methodology on habitat components and taken comments from a number of fora on the broader application, it was suggested that all components should be as‐
sessed twice; once based on an aggregate response and once a worst‐case (see Chap‐
ter 3 in Robinson et al., 2008b). As an example, if considering the effect of the pressure
‘abrasion and other physical damage’ (as caused by dredging (fishing)) on the sub‐
tidal rock component, the aggregate response would be based on the majority re‐
sponse of all subcomponents in the region being assessed, while the worst‐case assessment would be based on the most sensitive subcomponent (here probably Modiolus beds if they were exposed to dredging in the area being assessed). In the aggregate assessment, if, by area, the majority (i.e., >50% of the total area of subtidal reef habitats) of the subcomponents had high resistance to the pressure, the overall component would be assessed to have high resistance. In the worst‐case example, if Modiolus beds were assessed against the threshold to have low resistance to the abra‐
sion caused by dredging, the overall component would be assessed to have low resis‐
tance.
6.2.3 REA 2009
The latest version of the REA methodology was specifically developed for an assess‐
ment of the status of, and key pressures on, eight broad ecosystem components in the OSPAR Regions. The WGECO review of the application of the REA, 2009 methodol‐
ogy in the OSPAR regional assessment (Section 6.3 below), focuses on issues related to the suitability of the methodology to assess consistently degree of impact across ecosystem components.
Major developments from the REA (2008b) version included the addition of a second threshold so that further discrimination could be given between pressures that cause
a negligible amount of impact, those that cause some impact and those that cause an unacceptable level of impact. Indicators and thresholds for both habitat and species group components were based on guidance from the Habitats Directive Favourable Conservation Status descriptors and the OSPAR Annex V Texel‐Faial criteria.
Habitat components
Habitat components were defined to include their physical and biological features. In terms of biological features this referred only to benthic invertebrate species and as‐
semblages, as associated fish and seabirds were covered elsewhere in the assessment.
Physical features (and biogenic habitat features) were covered by all three of the indi‐
cators (range, extent and condition), while biological features were covered mainly by the ‘condition’ indicator (Table 6.2.3.1. below).
The condition indicator is based on the area of habitat damaged, where damage was defined as having occurred where “there has been a change in, or loss of, typical or natural elements (e.g., species, physical structures) of the habitat relative to former natural conditions such that structure and/or functioning of the habitat is altered. In terms of a change in biological structure (e.g., species composition), damage is as‐
sumed to have occurred where several typical species of the assemblage have been extirpated from the area. This does not include short‐term fluctuations in species whereby a species may be present in one year, absent in the next and present the fol‐
lowing year. It must be an example where there has been a sustained change in the composition of species.” (Robinson et al., 2009, Annex 2).
Table 6.2.3.1. Criteria used to assess the degree of impact of pressures on habitat components as taken directly from the REA, 2009 methodology and applied in the Utrecht OSPAR QSR2010 workshop.
Degree of Impact Threshold
descriptor
No/Low Moderate High
(i) Range Geographic range of habitat is stable (loss and expansion in balance) AND not smaller than former natural conditions
Geographic range of habitat has decreased <10%
relative to former natural conditions AND is not stable
Geographic range of habitat has decreased >10%
relative to former natural conditions
(ii) Area within
range (extent) Total area of habitat is stable (decreases and increases in balance) AND negligible (<1%) loss in total surface area relative to former natural conditions.
Some loss (<10%
X >1%) in surface area relative to former natural conditions
Large loss in surface area (>10% relative to former natural conditions)
(ii) Condition (damage)
Structures and functions (including typical species) in good condition, with small areas (<10% in total) considered to be damaged.
Between 10-25%
of the total area of the habitat is damaged.
Large area of habitat (>25%) is currently damaged1 relative to former natural conditions
Species components
Species group components included all species represented by the broad ecological components ‘Fish’, ‘Seabirds’, ‘Cetaceans’ and ‘Seals’.
Table 6.2.3.2. Criteria used to assess the degree of impact of pressures on species group compo‐
nents as taken directly from the REA, 2009 methodology and applied in the Utrecht OSPAR QSR2010 workshop.
Degree of Impact Threshold
descriptor No/Low Moderate High (ii) Range <10% of species have
range declines >10%
compared to former natural conditions.
10-50% of species have range declines >10%
compared to former natural conditions
>50% currently have range declines >10% compared to former natural conditions.
(iii) Population size (extent)
<10% of species currently have a large decline in population size (>25% relative to former natural conditions)
10-50% of species currently have a large decline in population size (>25% relative to former natural conditions)
>50% of species currently have a large decline in population size (>25%
relative to former natural conditions)
(iv) Population
condition <10% of species have strong deviations in reproduction, mortality or age structure relative to former natural conditions1
10-50% of species have strong deviations in reproduction, mortality or age structure relative to former natural conditions1
>50% of species have strong deviations in reproduction, mortality or age structure relative to former natural conditions1
1Trend information required for clear deviation in reproduction, mortality or age structure showing
a significant deviation from former natural conditions.