Luciano B. Mendes & Wilfried Winiwarter
In this paper, we develop the framework of a system dynamics-based model for future studying the equity of resource distribution in rural areas, at a country scale and farm resolution. Our main hypothesis for conceptual development of the model is the following: the unequal spatial distribution of N fertilizer availability and use within a country might be linked to an unbalanced distribution of income to farms (in terms of farm size, i.e. economies of scale), which at the same time, might lead to exacerbated pollution. In such a context, our target variables are: nitrogen fertilizer use, farm size (both in land area and herd size) and emissions of NH3, N2O and CH4, all disaggregated in a per-country basis. The Causal Loop Diagram (CLD) approach was used for this study, for visual representation of our ‘model concept’ on how target and intermediate variables are related. In order to allow future calibration and/or validation of the dynamic model, all variables utilized in construction of the CLD are commonly used indicators of social and rural development, economies of scale at farm level and environmental impacts. The representation of our model into a CLD revealed that a more sophisticated representation of wealth distribution in farms may be needed to extend beyond trivial outcomes in modelling effects of N fertilizer use.