International Society for Ecological Economics Internet Encyclopaedia of Ecological Economics Agent-Based Modelling Entry prepared for the Internet Encyclopaedia of Ecological Economics

1. Introduction Agent-based modelling (ABM) is the computational study of social agents as evolving systems of autonomous interacting agents. ABM is a tool for the study of social systems from the complex adaptive system perspective. From this perspective, the researcher is interested in how macro phenomena are emerging from micro level behaviour among a heterogeneous set of interacting agents (Holland, 1992). By using ABM as computational laboratories, one may test in a systematic way different hypotheses related to attributes of the agents, their behavioural rules, and the types of interactions, and their effect on macro level stylized facts of the system. Since the early 1990s ABM has increasingly been used in most of the social sciences. I shall focus on the applications of ABM related to ecological economics (Janssen, 2002, 2005; Janssen and Ostrom, 2005). ABM of ecological economic systems can be defined as systems that are populated with heterogeneous population of agents, who determine their interactions with other agents and with their environment, on the basis of internalized social norms and mental models, internal behavioural rules and cognitive abilities, formal and informal institutional rules that affect how agents interact, individual and social learning, etc.