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SUSTAINABLE SYSTEMS THEORY
Citation:
Cabezas*, H C., C. W. Pawlowski**, A Mayer**, AND T Hoagland*. SUSTAINABLE SYSTEMS THEORY. Presented at Symp. on Managing risk in an Uncertain World, Evanston, IL, 05/31/03.
Description:
While sustainability is generally associated with the definition given by the World Commission on Environment and Development (1987) namely development that "meets the needs and aspirations of the present without compromising the ability to meet those of the future," it is important to recognize that a mathematical theory embodying these concepts would be immensely valuable in humanity's efforts to manage the environment. The concept of sustainability applies to integrated systems comprising humans and the rest of nature. The structures and operation of the human component (society, economy, law, etc.) must be such that these reinforce or promote the persistence of the structures and operation of the natural component (ecosystem trophic linkages, biodiversity, biogeochemical cycles, etc.). Thus, one of the challenges of sustainability research lies in linking measures of ecosystem functioning to the structure and operation of the associated social system. We propose that indicators based on Information Theory can be used to develop measures that bridge the natural and human system elements, and make sense of the disparate state variables of the system. Thus, we examine the use of Fisher Information which is a statistical measure of variation based on the probability distribution function for the states of the system. We have developed a novel approach to using Fisher Information for dynamical systems, which, borrowing from statistical mechanics, uses an ensemble average of the system dynamics. We demonstrate this methodology using an uncalibrated 5-trophic level, 10-compartment (species) food web model with an associated basic socio-economic system for the population of humans at the top of the food chain. The model has five functional groups: detritus, primary producers, herbivores, carnivores, and omnivores/humans. In addition to a seasonal forcing function, perturbation scenarios involving each of the parts of the system are simulated so as to explore the sustainability of the system under various types of stress. Since Fisher Information tracks the variation in a system, we hypothesize its use as an index of system sustainability. One critical challenge that arises in Sustainable Systems Theory is uncertainty. The challenge is that for the complex ecological-social-economic relevant to sustainability we have: (1) difficulty determining the appropriate state variables of the system, (2) difficulty accurately measuring any state variables, and (3) missing relationships between the state variables of the system. All these contribute to major uncertainty in the accuracy and usefulness of any model, result, or simulation. This is inherent to the nature of the system. Yet the question of sustainability is so critical to the future existence of humanity, that the scientific community would default in its most basic responsibilities by ignoring the issue.