FALLOW model: assessment tool for landscape level impact of farmer land use choices

Abstract: FALLOW is a landscape-dynamics model, which comprises the following main annual dynamic processes: (1) plot-level soil fertility dynamics in crop and fallow phases affecting agricultural crop production; (2) food storage, use and sale at the village level, with options along the spectrum from ‘full dependence on local food production ’ to ‘fully market-integrated ’ economy; (3) farmer decisions on increase or decrease of the area cropped, depending on labour availability and expected profitability of various land use options, as they have learnt from past experiences within the simulation; (4) spatial implementation of choices for land clearing land; and (5) impact assessment of how the resultant mosaic of land cover will affect watershed functions (annual water yield, base flow, net sediment loss), biodiversity indicators and carbon stocks. Initially developed as a Stella model, FALLOW has now been re-implemented in the spatially explicit modelling environment of PCRaster, making it possible to apply the model to larger landscapes with real spatial data sets. FALLOW can be used for impact assessment and scenario studies, assisting the negotiation process between stakeholders in a changing landscape by visualizing possible/likely consequences of factors such as changes in prices, population density and human migration, availability of new technology, spatial zoning of land use, pest and disease pressure or climate. We describe an application for the meso-scale catchment of a coffee producing area in Sumberjaya, Lampung, Sumatra, predictin