Exploring the Geographic Consequences of Public Policies Using Evolutionary Algorithms

Abstract

Public policies with geographical consequences are often difficult to analyze because they affect multiple stakeholders with competing objectives. While such problems fall conceptually into the domain of multiobjective evaluation, associated analytical techniques often search for a single optimum solution. Within the context of geographical problems, optimality often means different things to different stakeholders and, thus, an optimum optimorum may not exist. In this article, we present a new technique based on an evolutionary algorithm (EA) that produces a large number of optimal and near-optimal solutions to a large class of land management problems. As implemented for this article, solutions represent landscape patterns that produce services that meet stakeholder needs to varying degrees. The construction of curves that illustrate the trade-offs among various services given limited resources is central to this approach. Decision makers can use these curves to help find solutions that strike a balance among conflicting objectives and, thus, meet stakeholder needs. To provide context to this work we consider the impact of the U.S. Department of Agriculture's (USDA) Conservation Reserve Program on rural landscapes. Three objectives are assumed: (1) maximize farm income, (2) maximize environmental quality, (3) minimize public investment in conservation programs; the first two are viewed as services desired by stakeholders. Analytical and visualization tools are developed to reduce the burden associated with exploring the large number of solutions that are produced by this technique. The results illustrate that the EA-based approach can produce results equal to and significantly more diverse than conventional integer programming techniques.

Key Words:

• spatial evolutionary algorithms
• multiobjective optimization
• decision support
• agricultural policy

Acknowledgments

The authors wish to thank the USDA, NSF, and EPA for their joint support of this project through the Water and Watersheds Program, Dr. Steven Kraft and Dr. Jeffery Beaulieu for their advice on issues of agricultural economics, Mr. Girmay Misgna for work on early versions of the EA code, and the reviewers for their thoughtful comments.