Interim report of the HELCOM CORESET project

mean impact means that there are either several low impacts present in the site or one heavy impact. Such
an approximation was seen rough but still applicable as a fi rst step towards more detailed assessments of
cumulative human impacts.
Classifi cation of Impacts
The candidate indicator uses four different impact categories (not impacted, low impact, medium impact
and high impact) to describe the cumulative impacts using mean and standard deviation to defi ne class
boundaries (Table 4.3). The border between low and medium was defi ned as “signifi cant impact”.
Technical details of the data handling and the GIS procedures are given in the section “Technical data”
below (some information still missing).
Table 4.3. A tentative classifi cation of impacts in the benthic cumulative impact index.
Category Cumulative impact score
Not impacted 0
Low impact 0 < à Mean
Medium impact Mean à Mean + standard deviation
High impact Mean + stdev à max. cumulative impact score
Approaches to set the GES boundary for the condition of benthic habitats
The HELCOM core indicators for BSAP and MSFD assessments have quantitative targets which defi ne the
boundary between GES and sub-GES. The MSFD GES criterion 6.1 of the EC Decision 477/2010/EU calls for
an indicator to measure “Extent of the seabed signifi cantly affected by human activities for the different
substrate types”. This means that two thresholds must be defi ned:
– the level of signifi cant impact (a precondition for the next defi nition) and
– the level for GES, i.e. the proportion of benthic habitats which is not signifi cantly affected.
The fi rst defi nition requires a thorough investigation of the impacts of different pressures on benthic habitats
(which depend on the habitat type). If aiming at perfection, one should also estimate the signifi cance
of synergistic impacts. At present, this information is not available and the CORESET project suggests using
mean cumulative impact to denote “signifi cant impact” (see also text above).
The second defi nition may be hard to set by ecological means. All anthropogenic impacts degrade the
habitat quality and it may be diffi cult to fi nd sudden drops in the habitat quality along the pressure-state
response curves. Another approach would be so-called “assessment of the ecological coherence” which
measures the size, number and connectivity of areas and which has been previously used for assessments
of MPA networks (see HELCOM 2010b and publications of the EU BALANCE project 13 ). A practical solution
is to select a basis which is also used in the EU Habitats Directive. Under the directive a habitat which
has 25% of area signifi cantly impacted is classifi ed to ‘Unfavourable - Bad status’. In this indicator we can
assume that 15% of the habitat area is allowed to be signifi cantly impacted and still be in good environmental
status, allowing some human use of the marine environment.
13 http://www.balance-eu.org/, particularly http://balance-eu.org/xpdf/balance-interim-report-no-25.pdf
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