Land in sight?: Achievements, deficits and potentials of continental to global scale land-use modeling

Land use plays a vital role in the earth system: it links human decision-making to the terrestrial environment and is both driver and target of global environmental changes. However, decisions about how much land to use where and for what purpose (and the related consequences) are still poorly understood. This deficit is in contrast to the fundamental need for global analysis of future land-use change to answer pressing questions concerning, e.g. future food security, biodiversity and climate mitigation and adaptation. In this review, we identify major achievements, deficits and potentials of existing continental to global scale land-use modeling approaches by contrasting current knowledge on land-use change processes and its implementation in models. To compare the 18 selected modeling approaches and their applications, we use the integration of geographic and economic modeling approaches as a guiding principle. Geographic models focus on the development of spatial patterns of land-use types by analyzing land suitability and spatial interaction. Beyond, they add information about fundamental constraints on the supply side. Economic models focus on drivers of land-use change on the demand side, starting out from certain preferences, motivations, market and population structures and aim to explain changes in land-intensive sectors. Integrated models seek to combine the strengths of both approaches in order to make up for their intrinsic deficits and to assess the feedbacks between terrestrial environment and the global economy. Important aspects in continental to global modeling of land use are being addressed by the reviewed models, but up to now for some of these issues no satisfying solutions have been found: this applies, e.g. to soil degradation, the availability of freshwater resources and the interactions between land scarcity and intensification of land use. For a new generation of large-scale land-use models, a transparent structure would be desirable which clearly employs the advantages of both geographic and economic modeling concepts within one consistent framework to include feedbacks and avoid redundancies.