SCIENCE CHINA Earth Sciences © Science China Press and Springer-Verlag Berlin Heidelberg 2014 earth.scichina.com link.springer.com *Corresponding author (email: hcy@bnu.edu.cn)  RESEARCH PAPER  doi: 10.1007/s11430-013-4799-7 Modeling the impacts of drying trend scenarios on land systems in northern China using an integrated SD and CA model HUANG QingXu, HE ChunYang * , LIU ZhiFeng & SHI PeiJun State Key Laboratory of Earth Surface Processes and Resource Ecology (Beijing Normal University), Beijing 100875, China Received June 7, 2013; accepted September 21, 2013 Climate-induced drought has exerted obvious impacts on land systems in northern China. Although recent reports by the In- tergovernmental Panel on Climate Change (IPCC) have suggested a high possibility of climate-induced drought in northern China, the potential impacts of such drying trends on land systems are still unclear. Land use models are powerful tools for as- sessing the impacts of future climate change. In this study, we first developed a land use scenario dynamic model (iLUSD) by integrating system dynamics and cellular automata. Then, we designed three drying trend scenarios (reversed drying trend, gradual drying trend, and acceleration of drying trend) for the next 25 years based on the IPCC emission scenarios and consid- ering regional climatic predictions in northern China. Finally, the impacts of drying trend scenarios on the land system were simulated and compared. An accuracy assessment with historic data covering 2000 to 2005 indicated that the developed model is competent and reliable for understanding complex changes in the land use system. The results showed that water resources varied from 441.64 to 330.71 billion m 3 among different drying trend scenarios, suggesting that future drying trends will have a significant influence on water resource and socioeconomic development. Under the pressures of climate change, water scar- city, and socioeconomic development, the ecotone (i.e., transition zone between cropping area and nomadic area) in northern China will become increasingly vulnerable and hotspots for land-use change. Urban land and grassland would have the most prominent response to the drying trends. Urban land will expand around major metropolitan areas and the conflict between ur- ban and cultivated land will become more severe. The results also show that previous ecological control measures adopted by the government in these areas will play an important role in rehabilitating the environment. In order to achieve a sustainable development in northern China, issues need to be addressed such as how to arrange land use structure and patterns rationally, and how to adapt to the pressures of climate change and socioeconomic development together. water resource constraints, land use dynamics, climate change, scenario simulation, drying trends in northern China Citation: Huang Q X, He C Y, Liu Z F, et al. 2014. Modeling the impacts of drying trend scenarios on land systems in northern China using an integrated SD and CA model. Science China: Earth Sciences, doi: 10.1007/s11430-013-4799-7 1 Introduction Global changes and rapid socioeconomic development over the past century have put increasing pressures on human- environment relations (IPCC, 2007; Turner et al., 2003). In China, one of the most prominent concerns is the climate- induced drought in northern China, a region which occupies about 51% of China’s total land area. In recent decades, drought in the region had severe effects on regional climate systems and ecosystems, including reduced precipitation, higher snowlines, drying rivers, shrinking lakes, desertifica- tion, and ecosystem degradation (Fu and An, 2002; Lin et al., 2004). According to incomplete statistical data, since the 1990s the drying trend in northern China has resulted in direct economic losses of 100 billion RMB annually (Fu and An, 2002). However, the future drying trend in this region is not clear. This uncertainty greatly impedes the designing and