Hotspots of uncertainty in land-use and land-cover change projections: a global-scale model comparison.

Model-based global projections of future land-use and land-cover (LULC) change are frequently used in environmental assessments to study the impact of LULC change on environmental services and to provide decision support for policy. These projections are characterized by a high uncertainty in terms of quantity and allocation of projected changes, which can severely impact the results of environmental assessments. In this study, we identify hotspots of uncertainty, based on 43 simulations from 11 global-scale LULC change models representing a wide range of assumptions of future biophysical and socioeconomic conditions. We attribute components of uncertainty to input data, model structure, scenario storyline and a residual term, based on a regression analysis and analysis of variance. From this diverse set of models and scenarios, we find that the uncertainty varies, depending on the region and the LULC type under consideration. Hotspots of uncertainty appear mainly at the edges of globally important biomes (e.g., boreal and tropical forests). Our results indicate that an important source of uncertainty in forest and pasture areas originates from different input data applied in the models. Cropland, in contrast, is more consistent among the starting conditions, while variation in the projections gradually increases over time due to diverse scenario assumptions and different modeling approaches. Comparisons at the grid cell level indicate that disagreement is mainly related to LULC type definitions and the individual model allocation schemes. We conclude that improving the quality and consistency of observational data utilized in the modeling process and improving the allocation mechanisms of LULC change models remain important challenges. Current LULC representation in environmental assessments might miss the uncertainty arising from the diversity of LULC change modeling approaches, and many studies ignore the uncertainty in LULC projections in assessments of LULC change impacts on climate, water resources or biodiversity.

Spatial Analysis of Cultural Heritage Landscapes in Rural China: Land Use Change and Its Risks for Conservation.

Cultural heritage landscapes are consistently perceived as landscapes of high value. However, these landscapes are very vulnerable to change. In China, rapid land use change, especially urbanization, has become one of the main challenges for the conservation of cultural heritage landscapes in rural areas. This paper focuses on the designated cultural villages in rural China by systematically analyzing the spatial distribution of the designated cultural landscape across the country and assessing the threats these traditional landscapes are facing under current and future urbanization and other land use pressures. Current designated cultural heritage landscapes in China are predominantly located in the rural and peri-urban regions of Central and South China and less frequently found in other regions. Especially in these regions risks to land use change are large. These risks are assessed based on observed recent land use change and land use model simulations for scenarios up to 2050. The risk assessment reveals that especially in Southeast China along the sea coast and near the cities along the Yangtze River, high pressures are expected on cultural heritage landscapes due to urbanization. At the same time, in Southwest China, especially in Yunnan and Guizhou provinces, high pressures due to other land use changes are expected, including land abandonment. This assessment gives direction and guidance toward the selection of the most threatened cultural villages for detailed investigation and additional protection measures.

A review of global potentially available cropland estimates and their consequences for model-based assessments.

The world's population is growing and demand for food, feed, fiber, and fuel is increasing, placing greater demand on land and its resources for crop production. We review previously published estimates of global scale cropland availability, discuss the underlying assumptions that lead to differences between estimates, and illustrate the consequences of applying different estimates in model-based assessments of land-use change. The review estimates a range from 1552 to 5131 Mha, which includes 1550 Mha that is already cropland. Hence, the lowest estimates indicate that there is almost no room for cropland expansion, while the highest estimates indicate that cropland could potentially expand to over three times its current area. Differences can largely be attributed to institutional assumptions, i.e. which land covers/uses (e.g. forests or grasslands) are societally or governmentally allowed to convert to cropland, while there was little variation in biophysical assumptions. Estimates based on comparable assumptions showed a variation of up to 84%, which originated mainly from different underlying data sources. On the basis of this synthesis of the assumptions underlying these estimates, we constructed a high, a medium, and a low estimate of cropland availability that are representative of the range of estimates in the reviewed studies. We apply these estimates in a land-change model to illustrate the consequences on cropland expansion and intensification as well as deforestation. While uncertainty in cropland availability is hardly addressed in global land-use change assessments, the results indicate a large range of estimates with important consequences for model-based assessments.