Modeling Historic Rangeland Management and Grazing Pressures in Landscapes of Settlement

Defining historic grazing pressures and rangeland management is vital if early landscape threshold crossing and long–term trajectories of landscape change are to be properly understood. In this paper we use a new environmental simulation model, Búmodel, to assess two contrasting historical grazing landscapes in Mývatnssveit Iceland for two key periods—the colonization period (ca. Landnám, A.D. 872–1000) and the early eighteenth century A.D. Results suggest that there were spatial and temporal variations in productivity and grazing pressure within and between historic grazing areas and indicate that land degradation was not an inevitable consequence of the livestock grazing introduced with settlement. The results also demonstrate the significance of grazing and livestock management strategies in preventing overgrazing, particularly under cooler climatic conditions. The model enables detailed consideration of historic grazing management scenarios and their associated landscape pressures

A grazing model for simulating the impact of historical land management decisions in sensitive landscapes: Model design and validation

This paper reports the construction and testing of a historical environmental simulation model, Búmodel (bú: Icelandic – farm estate or enterprise). The model permits the investigation of historical grazing management under variable environmental conditions in Iceland through the prediction of spatial and temporal patterns of vegetation biomass and utilisation. Input parameters of the model are environmental, livestock and management variables from historical and archaeological sources. Process sub-models were constructed using contemporary Icelandic data. Validation of the model was based on an independent, published grazing experiment and demonstrated that Búmodel-predicted utilisable biomass values and biomass intake values fall within ±1 standard deviation of observed values. Búmodel provides a validated representation of linkages between environmental and management elements in a historical grazing system. It incorporates key issues of spatial and temporal scale, data quality, model validation and the inherent stochasticity of landscape change over historical periods. In doing so, it enables researchers interested in past landscapes to investigate the flexibility of the historical Icelandic grazing systems within the constraints of climate and vegetation cover, and provides a framework and methodology that can be applied to other historical extensive livestock-based agricultural systems