Geoscience Reference
In-Depth Information
each with the statistical probability that this outcome will materialize. Thus the
choice with the highest expected benefit to one or more groups of people
represents the optimal course of action, although this applies only in the
immediate future and only takes into account human aspirations. Many or all of
the choices included could conceivably be disastrous in a longer term.
This approach, using risk analysis, presumes that we know the probability
distribution of different outcomes, which we may not (Kahneman & Tversky
1979). If the mechanisms leading to different outcomes are not sufficiently
understood, no one can determine the probability that a particular outcome will
follow from a decision (Walker et al . 2003). Hence, the poorer the understanding,
the more uncertain are the predictions. This presents major challenges to
governments and regulatory agencies.
However, uncertainty varies not only by level but also in nature. Uncertainty
may reflect inadequate knowledge, or it may reflect inherent variability in human
and natural systems (Walker et al . 2003). At least three sources of variability may
be at play: randomness of natural processes; human behaviour, which often
deviates from the rational model of decision making; and interacting social,
economic and cultural phenomena. Uncertainty resulting from inadequate
knowledge may be remedied or reduced through research. On the other hand,
uncertainty owing to inherent variability is beyond management control and
cannot be reduced. Uncertainty generally increases as the period of the policy or
management decision extends into the future (Brewer 2007). This is because the
availability of reliable data diminishes as decisions reach further into the future,
and potential variability also increases over longer periods.
For freshwater ecosystems, the understanding of structure and function under
current conditions is quite far advanced, and the remaining uncertainty can be
reduced through further research. Likewise, the impact of key direct drivers of
aquatic ecosystem change is well understood. Such drivers include, for example,
temperature, hydrology, nutrients, acid deposition and toxic substances. By
comparison, the impact of indirect drivers, such as the effects of climate change
on agricultural practices and land use, and other social and economic changes,
are less well understood.
Individual and social behaviours vary enormously. For example, the contribution
to global food price increases of the recent expansion of biofuels production was
not widely foreseen. Land-use patterns and nutrient levels may be affected by
policies directly seeking to regulate them, but they are also affected by socio-
economic factors that determine the relative costs and benefits of different
farming options. Further, human behaviours acting as drivers of ecosystem change
are shaped by individual, professional and cultural norms, for instance those
concerning good agricultural practices (Nielsen 2009). Thus the impact of human
action on aquatic ecosystems represents a significant source of uncertainty.
Climate change is currently the most evident source of uncertainty. Recent
assessments of climate changes in Europe conclude that temperatures are likely
to increase by 2.1 °C-4.4 °C by 2080 and that precipitation will either increase or
decrease depending on the particular region (EEA 2007). Furthermore, it is
predicted that extreme weather incidents will become more frequent. However,
predictions for both temperature and precipitation changes are characterized as
Search WWH ::




Custom Search