Environmental Engineering Reference
In-Depth Information
example, while climatic conditions are now less stationary, trends are still noticeable.
Flood severity and frequency are changing, leading to alterations of floodplain desig-
nations. Timing of flowering, bird migration, and lake freeze-up are also changing ac-
cording to noticeable trends. Identifying this evidence can be important for demon-
strating and communicating the necessity of efforts to restore rare ecosystems and
ecosystem services that become scarcer under changing conditions and more crucial
to society. For example, restored floodplains and their floodwater storage and con-
veyance become more important as flood severity and frequency increase.
Climate Change and Varying Levels of Understanding
From a restoration planning and implementation perspective, climate change is prob-
lematic because we have varying levels of understanding about its timing, frequency,
and severity. Different levels of understanding about future conditions require differ-
ent approaches. We can categorize these levels of understanding by considering the
terms: risk, uncertainty, ignorance, and ambiguity (fig. 13.1).
Risk
refers to conditions
where the full range of possible outcomes and their probabilities are known. People
often use the term to focus on the share of outcomes seen as undesirable, but both po-
tential positive and negative outcomes should be included in a full evaluation of risk.
Uncertainty
refers to conditions under which the range of possible outcomes is
known, but their probabilities are not (Knight 1921). Because it is rare to have suffi-
cient information to know the probabilities of outcomes under unprecedented condi-
tions, uncertainty is common for climate effects, particularly for local considerations.
Ignorance
refers to situations where we do not know the possible outcomes. Condi-
tions of risk and uncertainty have known unknowns, while conditions of ignorance in-
volve unknown unknowns (Farber 2010). A situation can be described as
ambiguous
when there are multiple models of the realm of possibility, potentially with varying
levels of information between them that yield differing predictions of future events
(Camerer and Weber 1992). For climate change the wide array of models attempting
Defi nition
Example
Climate Risk
Probability that climate change will
lead to undesirable outcomes
Projected increases in the prob-
ability of future drought severity
and frequency
Climate Uncertainty
Possible outcomes of climate
change without known probabilities
of occurrence
Unknown future river flooding
severities and frequencies
Climate Ignorance
Unknown possible outcomes of
climate change
Unknown future effects on
ecosystem interactions
Climate Ambiguity
Confl icting predictions of climate
change outcomes or probabilities
Climate models with strongly differ-
ing future temperature predictions
FIGURE 13.1.
Restoration planners face varying degrees of information availability regarding
future impacts of climate change. The variation can be categorized by whether or not proba-
bilities of events are known, whether or not the set of possible outcomes is known, and
whether or not there are conflicting predictions.
