Figure 2.2 Land change modeling approaches (outer circle) placed within the context of the policy-and decision-making cycle (inner circle). SOURCE: modified from Verdung, 1997.
agent-based models, and hybrid models provide capabilities that can be exploited for assessing the possible effects of the policy, ex ante. For example, the GTAP model (Hertel, 1997), which is a static multi-region, multi-sector, CGE model, was used to evaluate the implications of biofuel mandates for land use demand both within the United States and internationally through the possible effects on the prices of food commodities (Keeney and Hertel, 2009).
Once policies or decisions have been implemented, the need for evaluating the effects of these implementations, ex post, is often quite effectively met through use of reduced-form economic models that estimate the magnitude of the effect of the intervention, usually by comparing observable outcomes either before and after the intervention or in an intervention area and some comparable