GMAA: A DSS Based on the Decision Analysis Methodology - Application Survey and Further Developments - Efficient Decision Support Systems: Practice and Challenges from Current to Future - page 278

of 1.9 m. The lagoon receives large (2 km 3 yr -1 ) freshwater inputs from the catchment, as well
as saltwater inputs through a sluice that connects the lagoon to the sea, see Fig. 15.
Ringkøbing Fjord has gone through two environmental regime shifts during the last
decades (Håkanson et al., 2007), which has stirred up public sentiment in the area, mainly
because of the disappearance of waterfowl.
The nine considered intervention strategies consisted of the abatement of nitrogen and/or
phosphorous, the construction and maintenance of a saltwater dumping station or a second
sluice to increase the water exchange between the lagoon and the outside sea and some
combinations of the above. All of them were aimed at achieving good water quality in terms
of trophic state and conditions for waterfowl and were compared with the no action
alternative and with decreasing the salinity level to 7.2 per thousand, the mean value in the
lagoon during the 12-year period preceding a major structural regime shift in 1996
(Håkanson & Bryhn, 2008; Petersen et al., 2008).
Intervention strategies were evaluated considering their environmental, social and economic
impacts. There were two attributes stemming from the environmental impact , natural TRIX
deviation and number of birds . The degree of eutrophication in a coastal area can be expressed
as a TRIX (TRophic state Index) deviation from the background value. The attribute
associated with this lowest-level objective represented the average TRIX deviation
regarding previous years over a 20-year period.
Another environmental impact we took into account was related to the sharp fall in
birddays over the year in recent decades. The associated attribute accounted for the number
of birds representing the average number of Bewick's swans and pintails living in the
lagoon in a year for the time period under consideration.
Regarding the social impact we made a distinction between the social impact for critical
population , i.e., people living around the lagoon that may be affected by the application of
intervention strategies, and collective social impact . Both subjective attributes account for
aspects like sentiment, possible employment associated with strategy application, crop
image…
Finally, the economic impact was computed by the average costs concerning the intervention
strategy application, i.e., nutrient abatement costs and/or construction and maintenance
costs for facilities.
Note that while the models or experts initially provided precise performances, imprecision
was introduced by means of an attribute deviation of 10% to evaluate the robustness of the
evaluation (see Table 4 in Jiménez et al., 2011).
Next, DM's preferences were quantified accounting for ecocentric, anthropocentric and
taxrefuser perspectives, which lead to different weight sets, and, finally, Monte Carlo
simulation techniques were applied. Fig. 16 shows the resulting multiple boxplot from both
perspectives.
Looking at the multiple box plots for the ecocentric and anthropocentric perspectives, we
find that S 5: Sluice and S 9: No action are ranked highest in both boxplots. S 8: 33% P abatement
+ Sluice is ranked highest from the ecocentric viewpoint, but its best ranking from the
anthropocentric perspective is fifth. Finally, S 6: Salt7.2 , with a best ranking of second from
the anthropocentric viewpoint, is ranked as the worst strategy from the ecocentric
perspective. S 5: Sluice and S 9: No action look better than the others. Moreover, the average
rankings for both are 1.011 and 2.489 from the ecocentric perspective, respectively, and 1.531
and 1.605 from the anthropocentric viewpoint. These results are even consistent regarding
the tax-refuser perspective, in which S 5 is better ranked (average ranking 1.246) than S 9