Sustainable systems theory: ecological and other aspects

Abstract

While sustainability is generally associated with the definition of sustainable development given by the Brundtland Commission ‘Our common future (1987) Oxford University Press,’ namely ‘development that meets the needs of the present without compromising the ability of future generations to meet their own needs,’ 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 (in terms of society, economy, law, etc.) must be such that these reinforce or promote the persistence of the structures and operation of the natural component (in terms of ecosystem trophic linkages, biodiversity, biogeochemical cycles, etc.), and vice versa. 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 bridge the natural and human system elements, and make sense of the disparate state variables of the system. Thus, in this paper we explore the use of Fisher Information, which is a statistical measure of variation, as an aggregating index for dynamic systems of many variables. We have developed a novel application of Fisher Information to time-series data of dynamic systems, which (borrowing from statistical mechanics) uses an ensemble average of the system dynamics. We demonstrate this methodology using an uncalibrated 5-trophic level, 12-compartment (species) food web model with an associated basic social system for the population of omnivores at the top of the food chain. The model has five functional groups: detritus, primary producers, herbivores, carnivores, and omnivores. 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, including basic human behaviors, such as agriculture. Since Fisher Information is a measure of the variation, we hypothesize that it is an indicator of system order, and thus system sustainability. This work is part of a multidisciplinary group at the U.S. Environmental Protection Agency's National Risk Management Research Laboratory.