Dual effects on vegetation caused by urban expansion in global drylands: Insights from the enhanced vegetation disturbance index

Abstract

Drylands account for approximately 40 % of the global vegetation productivity and serve as critical regions for advancing global sustainable development. In the context of rapid urbanization, accurately evaluating the urban expansion-induced effects on vegetation in drylands helps optimize urban land use and foster sustainable growth in dryland cities. Focusing on the rapidly urbanizing and ecologically fragile global drylands, this study evaluated the positive and negative effects on vegetation caused by urban expansion based on the enhanced vegetation disturbance index. The results revealed that global drylands underwent substantial but uneven urban expansion for the period 2000–2020, with urban land increasing from 91,869 km² to 199,013 km², a growth of 107,144 km², reaching an annual expansion rate of 3.9 %. Urban expansion-induced negative effects covered 13,427 km², concentrated in semiarid and dry subhumid regions, while positive effects encompassed 10,545 km², mainly distributed in semiarid regions. Across the spatial gradient from dry subhumid to hyper-arid regions, the effects on vegetation gradually shifted from being predominantly negative to predominantly positive. Climatic conditions and human activities jointly shaped the different effects on vegetation in drylands. These different effects may lead to complex consequences. Therefore, it is suggested to implement scientific land planning and efficient resource utilization during urban expansion in drylands, focusing on protecting existing vegetation, reasonably increasing urban green space, and promoting the coordination of ecological conservation and socio-economic development to ensure the long-term sustainability of dryland cities.