Development and use of a framework for characterising computer models of silvoarable economics

A review of existing computer models of silvoarable economics was undertaken for a project, entitled Silvoarable Agroforestry for Europe (SAFE), which aims to reduce uncertainty regarding the introduction and management of silvoarable systems in Europe. Because the published literature describing and comparing such models is sparse, a framework was developed and then used to characterise five computer models: POPMOD, ARBUSTRA, the Agroforestry Estate Model, WaNuLCAS, and the Agroforestry Calculator. Key characteristics described for each model were the background, systems modelled, objective of the economic analysis, economic viewpoint, spatial and temporal scales, generation and use of biophysical data, model platform and interface, and input requirements and outputs. Each of the models could produce a partial budget of the profitability of a silvoarable, arable, or forestry system at a one-hectare level using discounted cost–benefit analysis. Whilst the research models undertook the analysis from a viewpoint of a generic farmer, models developed for decision-support also included appraisals from the perspectives of tenants, share-croppers, and participants in a joint-venture. The two farm-scale models, ARBUSTRA and the Agroforestry Estate Model, could also be used to examine the feasibility of silvoarable systems on an existing business, and to determine the effects of heterogeneous land types and phased planting. The framework allows users to identify the pertinent issues for selecting or developing a particular model.