integration). The focus of problem formulation is on the development of
appropriate conceptual models (discussed below) that clearly describe the
potential causal linkages between the ecosystems and ecological attributes
at risk, the stressors potentially affecting these ecosystems and attributes,
the scientific bases for analyses, and the particular management issues
being addressed. Quite different model needs exist for the analysis and
characterization phases. For the analysis and risk characterization phases,
model needs focus on the development, availability, and application of
quantitative models that address the selected ecological endpoints and
can assess the condition of those endpoints in the context of reference,
benchmark, and desired ecological conditions. For these more quantitative
and predictive models that are useful for the analysis and integration phases
of the ecological risk framework, the central issue is the degree of confidence scientists, stakeholders, and decision makers have in the model
results.
5.1.2 Utility of Conceptual Models
The term conceptual model can be viewed as qualitative or descriptive statements or hypotheses concerning the nature of causal relationships among
human activities, the resulting anthropogenic stressors, and their impacts on
human and ecological systems (USEPA 1992, 1998; Barnthouse and Brown
1994; C. Harwell et al. 1999a; Suter 1999a,b; Foran and Ferenc 1999; Harwell
and Gentile 2000; Gentile et al. 2001). Conceptual models are an especially
important initial step in the analysis of multiple stressors and of the cumulative ecological effects as well as in understanding the ecological consequences of management alternatives at regional scales. For site-specific
environmental assessments, conceptual models should be developed as a
tool for describing the causal relationship between human activities, environmental stressors, at-risk valued ecological resources, and their associated
ecological endpoints and measures. This tool can then be used for a variety
of management and communication purposes. A properly developed
conceptual model effectively captures the scientific understanding of an
ecosystem and its response to natural and anthropogenic stressors. The
process of constructing a conceptual model can engage the scientific
community in an important dialogue to articulate more clearly the individual perspectives of scientists regarding how an ecosystem functions and
responds to stress. Assumptions and proposed relationships must be made
explicit and defended, and in the process, a consensus of the scientific community may emerge. The conceptual model can do much more, however. It
can be an extremely effective tool for communicating to nonscientists or
to scientists who have not previously focused on the environmental
problem at hand. The communication function is very important for this
class of complex problems for the very reason that they are complex, and
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Mark A. Harwell and John H. Gentile
appropriate conceptual models (discussed below) that clearly describe the
potential causal linkages between the ecosystems and ecological attributes
at risk, the stressors potentially affecting these ecosystems and attributes,
the scientific bases for analyses, and the particular management issues
being addressed. Quite different model needs exist for the analysis and
characterization phases. For the analysis and risk characterization phases,
model needs focus on the development, availability, and application of
quantitative models that address the selected ecological endpoints and
can assess the condition of those endpoints in the context of reference,
benchmark, and desired ecological conditions. For these more quantitative
and predictive models that are useful for the analysis and integration phases
of the ecological risk framework, the central issue is the degree of confidence scientists, stakeholders, and decision makers have in the model
results.
5.1.2 Utility of Conceptual Models
The term conceptual model can be viewed as qualitative or descriptive statements or hypotheses concerning the nature of causal relationships among
human activities, the resulting anthropogenic stressors, and their impacts on
human and ecological systems (USEPA 1992, 1998; Barnthouse and Brown
1994; C. Harwell et al. 1999a; Suter 1999a,b; Foran and Ferenc 1999; Harwell
and Gentile 2000; Gentile et al. 2001). Conceptual models are an especially
important initial step in the analysis of multiple stressors and of the cumulative ecological effects as well as in understanding the ecological consequences of management alternatives at regional scales. For site-specific
environmental assessments, conceptual models should be developed as a
tool for describing the causal relationship between human activities, environmental stressors, at-risk valued ecological resources, and their associated
ecological endpoints and measures. This tool can then be used for a variety
of management and communication purposes. A properly developed
conceptual model effectively captures the scientific understanding of an
ecosystem and its response to natural and anthropogenic stressors. The
process of constructing a conceptual model can engage the scientific
community in an important dialogue to articulate more clearly the individual perspectives of scientists regarding how an ecosystem functions and
responds to stress. Assumptions and proposed relationships must be made
explicit and defended, and in the process, a consensus of the scientific community may emerge. The conceptual model can do much more, however. It
can be an extremely effective tool for communicating to nonscientists or
to scientists who have not previously focused on the environmental
problem at hand. The communication function is very important for this
class of complex problems for the very reason that they are complex, and
94
Mark A. Harwell and John H. Gentile