The impairment of environmental sustainability due to rapid urbanization in the dryland region of northern China

Rapid urbanization has been taking place in the world's drylands where water and other essential natural resources are scarce. Assessing the environmental impacts of urban expansion is highly important for the sustainable development of these dryland regions and beyond. Thus, this study aimed to assess the effects of urban expansion on environmental sustainability in the agro-pastoral transitional zone of northern China (APTZNC), a major dryland region of China. We first analyzed the patterns and modes of urban expansion and estimated the dynamics of environmental sustainability by integrating indicators of the environmental elements of water, land, air, and biodiversity from 2000 to 2015. Then, we assessed the impacts of the overall process and the different modes of urban expansion on environmental sustainability based on structural equation models. We found that the APTZNC experienced rapid urban expansion dominated by the edge expansion and leapfrog modes. The urban land area increased from 2169 km² to 6128 km² at an annual growth rate of 7.17%. This rapid urban expansion had significantly negative influences on environmental sustainability with a path coefficient of −0.98 (P < 0.001), leading to a decline of the comprehensive index of environmental sustainability from 64.22 to 50.77, a decrease of 20.93%. We also found that the three urban expansion modes had different effects on environmental sustainability, where the leapfrog mode had the greatest effect, followed by the edge expansion mode. Thus, effective management is needed to increase urban land efficiency and optimize urban land patterns to promote the sustainability of urban expansion in the APTZNC.