Stochastic model for a dynamic ecosystem

Because of increasing concern for our environment, the American public, through its governing bodies, is preparing to invest vast quantities of the nation's resources in the prevention and control of water pollution, as well as the control of air, noise, and radiation pollution, and sol id waste disposal. To have wise choices made in expending these resources, it is necessary first to understand the relationship between the discharge of pollutants into a body of water and the ultimate effect on the quality of that water. Once the cause-effect relationship is known, the effectiveness of a prospective pollution-control investment can be evaluated before the investment is made. In this way the best of many alternate control schemes could be selected for a given locality based on the needs, resources, and conditions of that locality. Usually, this cause-effect relationship is expressed in the form of a mathematical model, where each known step, process, mechanism, etc., is represented by a corresponding mathematical analog. Obviously, the better the pollution mechanism is understood, the more accurate its translation into a mathematical analogue, and thus, the more reliable the comparison of the alternatives. It is also evident that a rigorous comparison must be made between any mathematical model and actual data before the model may be confidently used in a predictive capacity.