1.3.1 The Nearshore Conceptual Model |
Conceptual models are often incorporated into all types of assessments as a device for describing the causal relationship among land use, stressors, valued ecological resources at risk, and their associated endpoints and indicators (Thom and Wellman 1997, Gentile et al. 2001). Regional assessments that involve conceptual models include May and Peterson’s (2003) Kitsap Salmonid Refugia Study, which integrates conceptual models of watershed function and salmon population dynamics to identify those habitats critical to sustaining remaining native salmonid populations. This nearshore assessment builds upon a summary of the best available science (BAS), which summarizes the existing scientific literature as it relates to the nearshore environment of Bainbridge Island (Williams et al. 2003). As such, the assessment employs the conceptual model of Williams and Thom (2001) to build a scientifically defensible framework for assessing the potential effects of changes to nearshore ecological functions caused by human modifications to nearshore habitats (Figure 1).
Figure 1. Basis of Conceptual Model (Williams and Thom 2001)
The nearshore conceptual model assumes that shoreline modifications exert effects at varying degrees on an ecosystem’s controlling factors (Figure 1; Table 1). Controlling factors (e.g., light level, wave energy) are physical processes or environmental conditions that control local habitat structure and composition (e.g., vegetation, substrate), including where habitat occurs and how much is present. In turn, habitat structure is linked to support processes, such as primary production or landscape connectivity, which influence ecological functions. Thus, impacts that affect controlling factors within an ecosystem are reflected in changes to habitat structure, and ultimately are manifested as changes to functions supported by the habitat. The effect at the functional level depends upon the level of disturbance and the relative sensitivity of the habitat to the disturbance.
Table 1. List of Major Controlling Factor, Habitat Structure, Habitat Process, and Ecological Function Metrics.
Controlling Factors |
Habitat Structure |
Habitat Processes |
Ecological Functions |
Wave Energy |
Density |
Production |
Prey Production |
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