From Bioeconomic Farm Models to Multi-Agent Systems: Challenges for Parameterization and Validation

Bioeconomic farm models have been very instrumental in capturing the technical aspects of human-nature interactions and in highlighting the economic consequences of resource use changes. They may elucidate the tradeoffs that farm households face in crop choice and farming practices, assess the profitability of various land-use options and capture the internal costs of adjusting to changes in environmental and market conditions. But they face also limitations when it comes to analyzing situations, in which heterogeneity of households and landscapes is large and increasing. Multi-agent models building on the bioeconomic farm approach hold the promise of capturing more fully the heterogeneity and interactions of farm households. The fulfillment of this promise, however, depends on the empirical parameterization and validation of multi-agent models. Although multi-agent models have been widely applied in experimental and hypothetical settings, only few studies have tried to build empirical multi-agent models and the literature on methods of parameterization and validation is therefore limited. This paper suggests novel methods for the empirical parameterization and validation of multiagent models that may comply with the high standards established in bioeconomic farm modeling. The biophysical measurements (here: soil properties) are extrapolated over the landscape using multiple regressions and a Digital Elevation Model. The socioeconomic surveys are used to estimate probability functions for key characteristics of human actors, which are then assigned to the model agents with Monte-Carlo techniques. This approach generates a landscape and agent populations that are robust and statistically consistent with empirical observations.