EU request to advise on methods for assessing adverse effects on seabed habitats

ICES advises on the suitability and shortcomings of different indicators and indicator methods for assessments of adverse effects on seabed habitats. The indicators are specifically evaluated for MSFD D6C3 and D6C5 assessments of (sub)regions and broad habitat types (BHTs). Performance is evaluated in gradient studies or relative performance ranking. Suitability is evaluated in terms of associated habitat properties, output type and scale, and potential use for setting ecologically-meaningful and quantitative thresholds.

Regional assessments would ultimately best be carried out by applying different indicators in a complementary manner. Systematic screening of indicators that cover different aspects of seabed habitat condition and benthic community properties may improve change detection as well as accuracy and confidence in assessments of human pressures. State-based and pressure-based assessment methods would be best implemented simultaneously, sequentially and/or iteratively to maximize operationality across regional, national, and local scales. 

ICES was unable to estimate and advise on robust quality threshold values. Appropriate thresholds for seabed habitat need to be relevant to the management aims (achieving GES), informed by ecological principles, and be ecologically meaningful, habitat-specific, and preferably derived from the objective analysis of ecological data, with uncertainty estimation.

ICES advises on the main components of a framework and a stepwise approach to evaluating methods that assess the state of seabed habitats and the effects of human pressures.

Current sampling effort and design is unlikely to provide an empirically-based, representative picture of seabed habitat status (state-based indicators) at the whole regional scale required for MSFD/D6 assessments. Guidance should be developed for strategic sampling that will facilitate data standardization between countries and ensure ground-truthing of analytical assessment outcomes (from pressure-based methods) in areas of extrapolations with high uncertainty.