Tools for Better Decision Making: Bridges from Science to Policy - Climate Change Impacts on Freshwater Ecosystems - page 264

'highly uncertain' (EEA 2007: 152). This uncertainty interacts with the inherent
variability of freshwater ecosystems as well human impacts on the drivers
discussed above. For instance, climate change may prompt migration of species
and new crop patterns, changing habitats, migration of pest species and
establishment of alien species. Likewise, extreme weather events might change
the resilience of natural systems, for instance to nutrient influxes. Overall,
extreme events could lead to non-linear pressures on existing systems, which
increase variability and impede predictability. These uncertainties bear on
assessments of mitigation costs and benefits. If the long-term effects of mitigation
measures cannot be predicted, it will not be possible to estimate the costs of
attaining a certain level of protection either.
Recognizing uncertainty as inherent in environmental policy formulation, the
EU applies the precautionary principle to decision making. The principle was
instituted in EU law with the Maastricht Treaty of 1992 (Treaty on European
Union (92/C 191/01) ) and is written in Article 174. The principle is not explicitly
defined in the treaty, but at its heart is the notion that policy action against
potential threats to the environment may be justified even without deterministic
scientific proof of harm, as expressed in the German word Vorsorgeprinzip , which
refers to acting with foresight (Andersen 2000; EEA 2001: 13). The Commission
states that the precautionary principle may be applied as 'a risk management
strategy' in some fields, specifically when scientific evidence is insufficient or
uncertain and there are reasonable grounds for concern (Commission of the
European Communities 2000: 10). Accordingly, measures adopted should be
proportionate with a 'desired level of protection' as opposed to zero risk and
they should rest on an examination of the benefits and costs of action or lack of
it. Finally, the Commission calls for continued scientific evidence to re-examine
policy measures. Thus, the EC use of the precautionary principle clearly holds
that scientific uncertainty cannot justify a lack of action, even while it holds that
scientific knowledge is the sine qua non on which to base any decision making.
However, in some circumstances, traditional methods for decision making, i.e.
those that aim to identify single optimal choices, may not be appropriate and so
alternatives must be found. One alternative is to use scenario-based analyses
that use models to explore the consequences of different policy or management
decisions under different scenarios. Rather than single-best policies, policy
analysts look for robust policies that perform satisfactorily across different
scenarios (Walker & Marchau 2003; Popper et al . 2005). Furthermore, scenario
analysis allows the relative importance of different components to be assessed
and makes transparent the trade-offs involved in each strategy. This potentially
enables more resilient outcomes.
Scenario building presupposes that, given a particular set of drivers, the future
can be predicted well enough to examine the outcomes of different policies across
the scenarios. Walker and Marchau (2003) question that robust policies can be
identified, particularly for climate change, and therefore question the value of
scenario approaches. They advocate instead a stepwise approach: 'Take those
actions now that cannot be deferred; prepare to take actions that may later
become necessary; monitor changes in the world and take actions when they are
needed' (Walker & Marchau 2003: 3).