Report of the Workshop on MSFD biodiversity of species D1 aggregation (WKDIVAGG)

The WKDIVAGG workshop was initiated to provide guidance on an appropriate method(s): a) to integrate across criteria for each species of bird, fish and cephalopod (excepting commercial species and species on Habitats Directive annexes); b) to aggregate species within species groups for an overall assessment of status per species group for MSFD Descriptor 1; c) to aggregate from species group to the level of birds, mammals, reptiles, fish and cephalopods for an overall presentation of the extent to which GES has been achieved for these higher groups.

The workshop brought together 26 experts from 11 European countries, chaired by Anna Rindorf (DK). The workshop participants considered the previous ICES advice on integration together with the new Commission Decision and suggested integration methods to integrate status from criteria to species, species to species group and from species groups to ecosystem component. Important considerations included the ro-bustness of the methods to measurement error to avoid false alarms (recording a poor status where the actual status is good) and missed alarms (recording a good status where the actual status is poor). The applicability of the methods to data limited situa-tions and the information inherent in specific patterns in species not in GES. For example, a single year with a species not in good environmental status (GES) may be caused by measurement error or random variation in species dynamics and is not perceived as a cause for alarm, whereas a string of years with not good status is likely to raise serious concerns. Further, a species for which an indicator is measured with low precision (high measurement error) will be particularly prone to both false alarms and missed alarms.

Two options were considered appropriate for integration at one or more levels. Both methods contain an aspect of proportion of species in good status. From criteria to spe-cies, five different options were proposed, each of which should be evaluated to determine the sensitivity to false alarms and risk of missing alarms.
It was considered essential that information on the proportion of species which were considered relevant but not assessed due to lack of data were retained. This often in-cludes species which have previously been abundant but are now too scarce to assess. Further, it is integral to the assessments that methods using proportional or averaging methods are supplemented by safeguards that monitor whether the non-GES status of species are consistent from one group, one area or one species through time.
The work commenced at WKDIVAGG will be continued in WKEXTINCT.