Models Supporting Decision-Making and Policy Evaluation - Environmental Modelling: Finding Simplicity in Complexity - page 321

specific concerns of the decision-maker (sectorally spe-
cific). Simulation models have the advantage of being
able to combine the general (rules, equations and rela-
tionships describing processes) with the highly specific
(geodata describing the condition - or state - of different
spaces and places). A class of simulation models that
are termed decision-support systems and policy-support
systems are targeted at making sophisticated descriptions
of process, state and change accessible in a dynamic way
to support decision-making in general, or the testing and
design of policies in particular.

implications of policy implementation can be very diffi-
cult to trace conceptually because the observed variability
yields complexity and scale-dependence in the policy
outcomes. Spatially explicit, data-based simulation tools
can help handle and communicate the outcomes of such
complexity over particular administrative or biophysical
regions. Such tools combine relatively generic rules for the
operation of biophysical and socio-economic processes
with highly specific, spatially explicit data on biophysical
and socio-economic properties. Policy-support systems
thus enable individual learning or co-learning of stake-
holder groups and can also provide project-specific advice
for the implementation of more robust and better tested
policy. They are - like all models - only as good as the
quality of abstraction, data, science and testing that under-
pin them. Whether they actually yield better policy will
depend on the quality of the PSS and the quality of the
institutional setting for policy.

20.1.1 What ispolicysupport?

Policy-support systems (PSS) are an extension of these
ubiquitous and highly variable decision-support sys-
tems (DSS). Decision-support systems can range from
simple flowcharts through to sophisticated geograph-
ical information systems (GIS)-based simulation tools
(see Chapter 21). Decision-support systems are usually
intended to assist decision making around a specific issue
such as whether or not to implement a specific land
management intervention (where to add dams, where to
permit irrigation, where to build terraces). Policy-support
systems, on the other hand, assist in the design of broader
policies such as how to best adapt agriculture to climate
change, how to achieve an optimal land-use planning or
the design of land-use incentive schemes. Such policies
might include a range of individual management actions
operating concurrently or sequentially.
Decision-support systems and PSS usually target the
technical assistants to policymakers and form only part of
the information input to the policymaking process. They
are not designed to 'advise' on which policy to adopt but
rather to act as a 'digital test bed' to understand better
the likely implications of adopting various policies, and
thus add to the weight of evidence in favour or against a
particular policy. The availability of a digital test bed is
particularly important where the policy involves a vari-
ety of landscapes, ecosystems, socio-economic activities
and stakeholders and thus the usual expert evaluations
and conceptual or stakeholder scenario analysis may
not identify all positive and negative outcomes of a
particular policy. The policy adopted may thus yield
unhelpful surprises upon implementation and one of
the purposes of DSS/PSS are to highlight these in silico 2
before they are manifested in vivo . Where landscapes are
spatially heterogeneous and/or temporally variable, the

20.1.2 What typesof support?

A number of well defined mechanisms exist to bet-
ter understand the likely impacts of infrastructural
investments. These mechanisms include Environmental
Impact Assessment (EIA - Holder, 2004), Environmental
and Social Impact Assessment (ESIA) and Strategic
Environmental Assessment (SEA), 3 which are routinely
employed at corporate or governmental levels in advance
of major infrastructure projects in order to minimize
associated risk or maximize associated benefits. Processes
such as integrated watershed management (Heathcote,
2009), and other such management mechanisms are
also directed to managing resources carefully in complex
circumstances. The EU Water Framework Directive 4
is another such mechanism. These mechanisms all
contribute to understanding and minimizing negative
impacts whilst making the most of opportunities.
None provides data and understanding for scenario
analysis of the proposed intervention but all provide a
legal, institutional or technical framework to facilitate
such analysis to take place. The key role of PSS is to
provide scientific support and to help bridge scientific
developments in the understanding of change in land-
scapes with operational decision-making in the policy
domain. As such PSS can contribute to many of these
management mechanisms and other policy-development

3 See http://live.unece.org/env/eia/eia.html (accessed 6 April 2012).
4 See http://ec.europa.eu/environment/water/water-framework/
index_en.html (accessed 6 April 2012).

2 Performed on a computer.