A bioeconomic systems approach to sustainability analysis at the farm leve

In this study, an integrated, whole-farm simulation model that links biophysical process models with a multi-period recursive programming model of farmer decision-making is developed to address farm-level sustainability questions. This model provides a framework with which to analyze the effects over time of a farmer's decisions regarding cropping patterns, cultural practices, and farming technologies as they relate to the sustainability of the farming system. Sustainability definitions and concepts are reviewed, particularly as they apply to farm-level analysis, which leads to a definition of sustainability that is operational at the farm level. The moral philosophy underpinning notions of sustainability is discussed and ethical issues relating to the obligation to the future are explored. Serious questions arise regarding the validity of standard discounting techniques and economic evaluation methods when applied to environmental and natural resource problems.;A sustainable farming system has four desirable properties: productivity, stability, resilience, and equity. These properties constitute the social value of the system, and their indicators should reflect the well-being of people and the environment. Based on these properties, indicators of farming system sustainability are defined such that they can be used systematically in a whole-farm sustainability model. The farm sustainability model developed in this study consists of an economic decision-making component and a simulation component that models biophysical processes and sets up the succeeding economic component. The IBSNAT crop models are used to simulate crop growth and the fate of soil nitrogen. The economic model is a multi-period nonlinear programming model with a chance-constraint on nitrogen leachate. The farm model is developed with a recursive structure and is locally optimizing, allowing for modification to parameters based on feedback from previous periods and the realization of yields and prices. An application of the integrated farm sustainability model to a hypothetical North Florida peanut farming system is illustrated, and it demonstrates the richness and flexibility of the approach to analyzing the sustainability of a farming system.