Tools for Better Decision Making: Bridges from Science to Policy - Climate Change Impacts on Freshwater Ecosystems - page 277

(e.g. small lakes, large rivers, wetlands) and the DSS tool indicates the ecosystem
variables that are likely to be sensitive to climate change. This information has
been collated from an extensive review of literature and expert judgement (Hering
et al. Chapter 5, this volume). The tool also suggests relevant variables that might
be used for monitoring these effects and provides a qualitative rationale for the
processes involved. In this way the DSS guides the user to include those elements
of the catchment that are sensitive to climate change into their analysis.
Using the information from this vulnerability analysis, and current management
problems within the catchment, the final preparatory step in the DSS application
is the definition of the scenarios, or management measures, that are going to be
compared using the DSS. These might be combinations of climate scenarios and
management measures applied to different extents. For instance, users may wish
to compare the effects of 50%, 100% or 200% increases in the area of riparian
wetland under different IPCC climate scenarios.
As the catchment area is divided into subunits (sub-catchments, administrative
units, etc.), these preparatory steps in the application of the DSS result in a set
of matrices, one for each scenario and management strategy, showing the
decision criteria for each spatial unit. The primary purpose of the DSS is to
provide a framework to facilitate a structured spatial analysis of these matrices.
The user populates the matrices by quantifying the decision criteria for each
scenario. This is done outside the DSS and can use a variety of different data
sources and approaches, including models, databases or expert judgement. The
particular mixture of information used to quantify the decision criteria will
vary from application to application, depending on the available data and
models.
Once the decision criteria have been quantified, the MCA tools within the
DSS can be applied. The value of each decision criterion is converted to a score
between 0 and 1 according to a function that is determined by the user of the
DSS. The function is intended to convey the relative preference for achieving a
certain value for the decision criterion. The form of these functions can be linear
or non-linear depending on the decision criteria being considered. Normalizing
the scores to the range 0-1 allows decision criteria with different units and
relating to environmental, social or economic considerations to be integrated
within a single analysis.
The decision criteria are also assigned weights. These weights are set by the
user and reflect the importance of the particular decision criteria to the overall
comparison of scenarios. For instance, the costs of implementing the measures
may be the overriding consideration and this decision criterion would be given a
higher weighting than others. Different interest groups may have different
priorities and these can be reflected in the choice of weights to determine if the
optimal management action is sensitive to the views of different groups. The final
MCA score is then calculated as a sum of each of the individual weighted decision
criteria scores. The results of the MCA are presented graphically, overlaid on the
GIS map showing the spatial units of the assessment.
The DSS has been tested for seven catchments across Europe, of which one is
presented here.