Interim report of the HELCOM CORESET project

38
Table 2.10. Pressures affecting the waterbird populations.
Species (wintering population) Anthropogenic pressure
Black-throated diver eutrophication, oil, by-catch
Red-throated diver eutrophication, oil, by-catch
Great crested grebe eutrophication, oil, by-catch
Goosander eutrophication, oil, by-catch
Red-breasted merganser eutrophication, oil, by-catch
Razorbill eutrophication, oil, by-catch
Common guillemot eutrophication, oil, by-catch
Black guillemot eutrophication, oil, by-catch
Velvet scoter eutrophication, oil, by-catch
Common scoter eutrophication, oil, by-catch
Long-tailed duck eutrophication, oil, by-catch
Eider eutrophication, oil, by-catch
Tufted duck eutrophication, by-catch
Greater scaup eutrophication, by-catch
Goldeneye eutrophication, by-catch
Mute swan eutrophication
Mallard eutrophication
Coot eutrophication
Because the pressures affecting the selected key seabirds in the winter populations are similar, it is possible
to make an index indicator where assessment can be fi rst made on the species level and then functional
groups are assessed separately. Finally, an integration of all the species can be made to describe abundance
of all wintering seabirds. How this integration will be made is not yet clear.
Because the species and functional groups may have different signifi cances in the ecosystem, weighting
factors should be considered. They could be based on the conservation value of the Baltic population in the
European context or the proportion of the species in the wintering seabird abundance.
Approach for defi ning GES boundaries
All the species or functional groups respond to anthropogenic pressures slightly differently, although the pressures
behind the change are similar. Therefore the targets, which show the boundary of GES, must be set for
each species separately. It is proposed that the GES boundaries are set on the basis of (1) time series data and
(2) relation to other indicators (e.g. nutrients, chlorophyll, zoobenthos, plant abundance, fi sh stocks).
The GES boundaries should be given separately for all the sub-basins of the Baltic Sea (see Figure). As
defi ning GES for all of the sub-basins may take time, the fi rst step should be to defi ne GES for those subbasins
which have highest abundance of seabirds in the winter.
Time series data: it is obvious that there are gaps in the time series datasets of wintering seabirds. The
available data sets should be used as far as possible, using also best estimates. Temporal trends should be
checked, because they show changes in the environment. Available sources of information are Skov et al.
(2000, 2007 and 2011).
Relations to other indicators: When assessing GES of the Baltic Sea, there should not be any mismatch
between GES of different indicators. For example, the nutrient concentration targets in the Baltic Sea have
been agreed in the HELCOM BSAP. Therefore, the seabird GES boundaries should not be set on levels
which cannot be reached when nutrient targets have been reached. In addition, competitive interactions
between fi sh feeding birds and large fi sh affect the target setting. With the current long-term management
plan of cod, the cod stocks will increase, which likely affects the food availability for birds. The GES
boundaries for birds should not be set too high in such conditions.