Uncertainties in global - scale reconstructions of historic land use

Land use and land-use change play an important role in global integrated assessments. However, there are still many uncertainties in the role of current and historical land use in the global carbon cycle as well as in other dimensions of global environmental change. Although databases of historical land use are frequently used in integrated assessments and climate studies, they are subject to considerable uncertainties that often are ignored. This paper examines a number of the most important uncertainties related to the process of reconstructing historical land use. We discuss the origins of different types of uncertainty and the sensitivity of land-use reconstructions to these uncertainties. The results indicate that uncertainties not only arise due to large temporal and spatial variation in historical population data, but also relate to assumptions on the relationship between population and land use. Improving empirical data to better specify and validate the assumptions about the relationship between population and land use while accounting for the spatial and temporal variation in this relationship could reduce uncertainties in the reconstructions. Such empirical evidence, needed to better parameterize reconstruction methods, could be derived from local case studies, such as those conducted in landscape ecology, environmental history, archeology and paleoecology.