relationships among historical, present, and potential future environmental
conditions. That is, the reference conditions provide the context for
evaluating environmental goals and the success or failure of management
to achieve those goals or desired ecological conditions (Harwell et al.
1999b). Again, a central objective for using models for ecological assessments would be to project the state of the ecological systems vis-à-vis those
reference, benchmark, and desired conditions. For example, the reference
conditions (Figure 5.3, rectangles) refer to both upper (minimal perturbation) and lower (maximum perturbation) bounding conditions for the
essential ecosystem characteristics of concern for the assessment. For many
situations, the upper boundary may be unattainable (e.g., restoring the
Everglades to 1800 predevelopment conditions). The lower boundary could
represent the elimination of the habitat completely. The desired conditions
(Figure 5.3, ellipses) are meant to represent the ultimate desired goal to be
achieved (the target state of the system at the completion of restoration).
In many cases, the extant ecological condition is far removed from the
desired condition, and progress towards restoration would be indicated
more clearly if a set of intermediate conditions were established as benchmarks or milestones for managers and scientists to assess the efficacy of
their actions and progress towards the goals. Note that benchmarks are
needed on both sides of the current condition to determine the direction
of response.
In addition, all states (reference, desired, current, and benchmark) have
both an ecological component and a stressor component. It is important to
note that nothing in this framework is meant to signify static conditions.
Rather, each benchmark or reference condition and the characterization
of the actual ecosystem explicitly incorporate natural variability as well
as processes like succession or other directional changes over time and
space.
The analysis phase of the ecological risk assessment focuses on developing and testing methods and models, conducting experiments, and analyzing data to characterize stress regimes and to establish stress–response
models. The ecological stress–response relationships are essential to predicting ecological consequences from resulting changes in the stress regime,
which provides the risk manager and decision maker the ability to evaluate, a priori, alternative management or remedial options.
Finally, risk characterization integrates stress and effects into a predictive and probabilistic statement of the risks and uncertainties that is to be
used along with societal and economic factors by the decision maker. As
such, the risk characterization phase of the risk assessment, like problem
formulation, is a critical point of intersection among the risk assessor, decision makers, and the public (NRC 1996).
Thus, when viewed from the ecological risk assessment perspective,
modeling needs in support of decision making differ for the different
phases of the assessment process (problem formulation, analysis, and
5. Overcoming Barriers to the Use of Models
93
conditions. That is, the reference conditions provide the context for
evaluating environmental goals and the success or failure of management
to achieve those goals or desired ecological conditions (Harwell et al.
1999b). Again, a central objective for using models for ecological assessments would be to project the state of the ecological systems vis-à-vis those
reference, benchmark, and desired conditions. For example, the reference
conditions (Figure 5.3, rectangles) refer to both upper (minimal perturbation) and lower (maximum perturbation) bounding conditions for the
essential ecosystem characteristics of concern for the assessment. For many
situations, the upper boundary may be unattainable (e.g., restoring the
Everglades to 1800 predevelopment conditions). The lower boundary could
represent the elimination of the habitat completely. The desired conditions
(Figure 5.3, ellipses) are meant to represent the ultimate desired goal to be
achieved (the target state of the system at the completion of restoration).
In many cases, the extant ecological condition is far removed from the
desired condition, and progress towards restoration would be indicated
more clearly if a set of intermediate conditions were established as benchmarks or milestones for managers and scientists to assess the efficacy of
their actions and progress towards the goals. Note that benchmarks are
needed on both sides of the current condition to determine the direction
of response.
In addition, all states (reference, desired, current, and benchmark) have
both an ecological component and a stressor component. It is important to
note that nothing in this framework is meant to signify static conditions.
Rather, each benchmark or reference condition and the characterization
of the actual ecosystem explicitly incorporate natural variability as well
as processes like succession or other directional changes over time and
space.
The analysis phase of the ecological risk assessment focuses on developing and testing methods and models, conducting experiments, and analyzing data to characterize stress regimes and to establish stress–response
models. The ecological stress–response relationships are essential to predicting ecological consequences from resulting changes in the stress regime,
which provides the risk manager and decision maker the ability to evaluate, a priori, alternative management or remedial options.
Finally, risk characterization integrates stress and effects into a predictive and probabilistic statement of the risks and uncertainties that is to be
used along with societal and economic factors by the decision maker. As
such, the risk characterization phase of the risk assessment, like problem
formulation, is a critical point of intersection among the risk assessor, decision makers, and the public (NRC 1996).
Thus, when viewed from the ecological risk assessment perspective,
modeling needs in support of decision making differ for the different
phases of the assessment process (problem formulation, analysis, and
5. Overcoming Barriers to the Use of Models
93