Ecosystem Services and Reallocation Choices: A Framework for Preserving Semi‐Arid Regions in the Southwest

摘要

Conservation of fresh water systems is a paramount issue in the semi-arid Southwestern U.S. (Department of Interior 2005). In these systems, ground water, surface water and flood regimes strongly influence the abundance, composition, and structure of riparian (streamside) vegetation, diversity and abundance of avian populations, and thus overall quantity and quality of system attributes and ecosystem services. Over time, these systems (Zekster et al. 2005) have been degraded by anthropogenic activities and, more recently, are threatened by climate change (Stromberg et al. 2007, Serrat-Capdevila et al. 2007, Alley et al. 2002).For water reallocation efforts to succeed in preserving these systems, a stakeholder community and/or policy maker requires a clear understanding of the management options available and a means to evaluate these options. Management options can be controversial, especially when the reallocation of existing water rights is required. One potentially effective approach is a Decision Support System, a class of interactive computerized information systems that support decision-making activities (Power 2002). For water management where ecosystem services are part of the decision-making criteria, a decision support system should have the capability of evaluating management options through the use of a series of coupled physical and ecological models that generate ecosystem service outputs. These outputs can then be reflected as monetized societal values for purposes of analyzing management options. However, ecosystem service values generally remain unknown relative to market values for goods and services.A primary focus of this paper is the value of ecosystem services and how they are derived from a broad base of scientific information. A central tenet of our efforts is that ecosystem values are appropriately driven by sound scientific information and thus values and sound science are inextricably linked. Valuation studies are typically conducted in the absence of integrated science information either because (1) targeted scientific research on the topic of interest is lacking, or (2) scientific studies that do exist have not been adequately designed to directly inform the valuation questions. We summarize previous scientific studies and present an approach in which ecosystem values are appropriately driven by these studies, and can feed back into a decision support system as a potential framework to help decision makers. We also focus on the process of transferring these values to other semi-arid areas, a key gap in our ability to use science and ecological valuation to help guide management in the region. Finally, in the conclusion, we touch upon the issue of integration of these values back into a decision support system for purposes of evaluating management options.Our starting point is an existing web-based decision support system that was developed with the Upper San Pedro Partnership (Yalcin and Lansey 2004).1 Our approach is summarized in Figure 1. The initial step, as detailed in Box 1, is to characterize the ecosystem. This requires an understanding of the components, processes within the system and its outputs. It is the outputs that are of central interest for valuation of ecosystems services. The next step (Box 2) is to develop scenarios. While restoration is a first and central goal in many systems, this represents only the beginning, not the end. Preservation of these systems in the face of dynamic climatic and anthropogenic effects is an important public policy issue. In the case of the San Pedro effort, we focus on ground water changes resulting from various anthropogenic changes. The third step (Box 3) is the coupled model of the physical and biological systems whose relationships are represented, often in simplified form, within the Decision Support System. This represents what might be termed “current conditions” of the overall system representing the understanding of the systems components an