Hastings (1994) considered there to be three broad ‘frameworks’ for the introduction of space into ecological models. The first of these is based on reaction diffusion systems, which may be either discrete or continuous in both time and space. A second approach is to consider changes in the occupation of different patches over time; such models may be termed patch occupancy or meta population models (Hanski and Simberloff, 1997). A third, and spatially explicit, approach is to use cellular automata or grid-based models; these may be individual-based or more aggregated.