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County and regional government agencies use stakeholder committees to ensure representation of diverse interests when planning, but these representatives often are not trained to understand the complexity inherent to human-environmental issues (e.g., groundwater management). Planning professionals use computer models to simulate the interaction effects of different planrelated policies, but most are "black boxes" to stakeholders, who, therefore, are forced to trust the simulations without understanding human-environmental complexity, reducing the opportunities for effective solution building. Agent-based models can represent decisions and environmental dynamics in a rule-based form that invites nonexpert users' involvement in both developing the model and meaningfully interpreting its outputs. We conducted a series of collaborative and developmental agent-based modeling meetings with stakeholders and planners in a rapidly suburbanizing area facing groundwater shortages. Stakeholders learned how to use the models, understand the relationships among the components, interpret the outputs based on these relationships, and suggested modifications with new insights. The enhanced understanding of complex interactions reduced early commitments to policy solutions as stakeholders jointly explored the range of possible outcomes. These results show that agent-based modeling holds promise for use in collaborative planning exercises. [ABSTRACT FROM AUTHOR]

An important debate in the literature on exurban sprawl is whether low-density development results from residential demand, as operationalized by developers, or from exclusionary zoning policies. Central to this debate is the purpose of zoning, which could alternatively be a mechanism to increase the utility of residents by separating land uses and reducing spillover effects of development, or an obstacle to market mechanisms that would otherwise allow the realization of residential preferences. To shed light on this debate, we developed an agent-based model of land-use change to study how the combined effects of zoning-enforcement levels, density preferences, preference heterogeneity, and negative externalities from development affect exurban development and the utility of residents. Our computational experiments show that sprawl is not inevitable, even when most of the population prefers low densities. The presence of negative externalities consistently encourage sprawl while decreasing average utility and flattening the utility distribution. Zoning can reduce sprawl by concentrating development in specific areas, but in doing so decreases average utility and increases inequality. Zoning does not internalize externalities; instead, it contains externalities in areas of different development density so that residents bear the burden of the external effects of the density they prefer. Effects vary with residential preference distributions and levels of zoning enforcement. These initial investigations can help inform policy makers about the conditions under which zoning enforcement is preferable to free-market development and vice versa. Future work will focus on the environmental impacts of different settlement patterns and the role land-use and market-based policies play in this relationship. [ABSTRACT FROM AUTHOR]

Environmental degradation is often defined as a public goods problem, emerging when property rights are not clearly defined and costs are externalized to other parties. Proposing corrective regulation that enforces technological fixes or market-based approaches is often met with political resistance and doubts about its effectiveness. This is partly due to the complexity of interacting physical and socio-economic components that obscure the impacts of human decision-making on environmental functions. Yet, understanding the complexity of integrated human-environmental systems can help planners and stakeholders frame environmental problems, view their role in them and design effective policies to address them. This article examines the potential and limitations of agent-based models as metaphors that can contribute to the understanding of such complex systems, illustrating the argument with a hypothetical application in groundwater management. [ABSTRACT FROM AUTHOR]