The analysis of the environmental and social impact of alternative management policies for coastal ecosystems requires, with increased urgency, a process of socioeconomic appraisal (or valuation) to obtain specific quantitative performance indicators to design effective management interventions. This paper proposes an integrated, ecosystem-based, functional, dynamic, anthropogenic approach to studying and analyzing the various factors, activities and processes that take place in the use and exploitation of coastal zones. This approach is applied to two sites (the Jucar River Estuary in Spain and the Patos Lagoon in Brazil) using a quantitative model that gathers and integrates the diverse range of interactions and functional relationships that shape and determine the ecosystem's performance (i.e. biological, environmental, economic, technological and social aspects) through an objective function. A net socioeconomic benefit function is postulated as the objective function to be optimized (maximized) over time, subject to the various constraints imposed by the legal and institutional framework, economic environment, resources, ecosystem dynamics and other factors. In both cases, four alternative management scenarios are considered.
The results show that improvements in water quality result in increased regional benefits in sectors that depend on water quality levels. In these cases, the marginal cost of cleaning up 1 m3 of water is lower than the marginal benefits obtained from 1 m3 of purified water. Therefore, the operation of water treatment plants improves the socioeconomic benefits to both regions by improving water quality (which in turn improves social welfare).