Sustainability indices with multiple objectives

One of the many debates about sustainability centers on how a natural resource stock (e.g. a forest) generates flows of desired human services (such as lumber and recreation). Should resources be sustained as they currently exist or should the services that they provide be sustained? This is a difficult question to address since there is very little quantitative information available. The purpose of this study was to address this question by using information from an empirical study that was able to look at sustainability when there is one output and extend that framework to a multiobjective setting. We then discuss the framework by using a multiobjective resource, the Neuse River in North Carolina.We identified several concepts from the single objective study, including that there are at least three important types of resource stocks, two types of goals, substitutes for natural resources, and a need to consider uncertainty and reversibility. An index of resource quality was used in a production model, which also allowed substitution of manufactured inputs to achieve the sustainability objective over long periods of time. The relationship between resource quality, manufactured inputs and output over time proved critical to meeting sustainability definitions and varied from one resource to another. When we expanded the framework, we found that constructing indices for one resource output might reveal that it is positively or negatively correlated to another output. For example, an index for drinking water might be made better through an indicator that is a positive, or negative, input into another index such as fishability.Sustainability should consider what is being sustained — i.e. stock, flow or something else, and be inclusive enough to account for multiple services, lest governments will under fund conservation (when services are positively correlated) or waste money by competing one objective against another (when they are negatively correlated) — addressing one objective through some policy requires more money in another government program to fix a problem that the first program caused. It should also be dynamic to allow for changes in relationships over time.