Applying Ecological Goal Functions: Tools for Orientor Optimization as a Basis for Decision Making Processes

The control of complex dynamic systems requires decisions which are based on multiple contradictory goals, on different evaluation procedures and on distinguished valuation scales. Particularly for ecosystems, these goals are influenced by a high number of uncertain state variables, by the dynamic characterization of system components and their interrelationships, by the kind of anthropogenic actions and by restricted information structures. Furthermore, decision making processes in ecology are coupled with difficulties in formulating ecological goal functions or orientors, where the economic consequences of management alternatives and the social benefits play an important role. Applying multicriteria decision making methods in ecology, optimal compromise solutions between ecological and man-made control operations will be obtained. Particularly methods which are related to Pareto optimality allow valuations of contradictory ecological goal functions. For example, the investigation of a river basin by water quality simulation models allow statements for single important variables of water quality and their ecological significance only Implementing a water quality model into a decision support system, allows (Pareto-) optimal values of the goal functions to then be computed. An example is presented on how to formulate goal functions for environmental protection and water quality management. Dissolved oxygen, biochemical oxygen demand, the amount of sewage water quantity and costs of enlargement of sewage treatment plants are taken into consideration. As a result, Pareto optimal solutions are computed for different ecological control strategies.