A process-led approach to modeling land change in agricultural landscapes: a case study from Madagascar

This study develops a model to predict pattern from process, providing a counterpoint to land-change studies that interpret process from pattern. This less-represented approach to land-change analysis uses theory to guide the characterization of land-cover patterns and to shape more directly the process–pattern relationships explored. The study presents a land-change model explicitly structured by a human–environment theory—the induced-intensification thesis of agricultural change. It uses the thesis to characterize the range of management strategies adopted by farmers in the Andapa region of Madagascar as they respond to rising land pressure. The study then identifies the particular land-cover consequences of each of these strategies. These farmer-level process–pattern linkages form the basis of an aggregate village-level land-change model, which predicts the land-cover outcomes of different dominant trajectories of agricultural change. The process-led model is found to be robust, successfully reproducing village-level landscape outcomes for most land-cover classes. Yet, the model also reveals that the dominant village-level process (the strategy followed by most farmers) does not necessarily create the spatially dominant land-cover outcome. This breakdown in the village-level process–pattern linkage occurs because of the well known, but often over-looked, methodological problem of the ecological fallacy. Aggregate variables reveal relationships at broader levels that do not necessarily parallel relationships found at the individual level. This study considers different types of aggregation effects, and clarifies why this case study is particularly susceptible to the adverse implications of the ecological fallacy. Despite these methodological issues, a process-led approach proves to be a valuable means to incorporate theory more explicitly into land-change models than achieved in pattern-led studies.