ABSTRACT
As defined in Chapter 1, economic value is based on change (e.g., in environmental quality). The change could be actual or proposed, from implementing a management alternative (e.g., planting a grass filter strip along a farm field near a stream to reduce runoff) to creating a new source of pollution. One potential tool that helps illustrate and communicate the changes is the conceptual model; it is a visual representation along with written descriptions of the relationships among sources or land uses, stressors (or pollutants), ecological entities, and their responses to the stressors. In this chapter, the typical conceptual model, as found in ecological risk assessment (e.g., see U.S. Environmental Protection Agency [USEPA] 1998), is expanded to include ecosystem services (e.g., ecosystem functions or processes that directly or indirectly affect an individual’s happiness or well-being), water quality standards (WQS), restoration actions, and economic endpoints.
