Helpful comments from Paul Atkins, Marco Janssen, participants at the joint CSIRO Agent-Based Modelling/Human Ecosystems Modelling with Agents (CABM/HEMA) Workshop, Canberra (17–18 May 2004) and at the IEMSS Congress, Osnabrück (14–17 June 2004) are gratefully acknowledged. The usual caveat regarding author’s responsibility applies.