Comparing the spatial and temporal dynamics of urban expansion in Guangzhou and Shenzhen from 1975 to 2015: A case study of pioneer cities in China's rapid urbanization

The distinct urbanization process of China has attracted worldwide attention because of its impressive speed, massive scale, and policy intervention. However, the interrelationship between urban expansion and government policies is still not well understood. The Pearl River Delta Urban Agglomeration of China is the first national pioneering urbanization area since the implementation of the policy Reform and Opening-up in the late 1970s. Here we compared the spatial and temporal patterns of urbanization in two leading cities of the Pearl River Delta (i.e., Guangzhou and Shenzhen, the provincial capital and the first Special Economic Zone of China, respectively) from 1975 to 2015, using Landsat data integrated with urban growth and landscape metrics analysis, and examined possible footprints of major economic and urbanization policies. Our results illustrated that urban land areas in both Guangzhou and Shenzhen have experienced magnificent annual growth rates at 8.1% and 11%, respectively between 1975 and 2015. On average, Shenzhen witnessed substantially higher urban growth rate than Guangzhou during the past four decades, particularly in the initial period (1978-1990) when the Reform and Opening-up policy was launched and Shenzhen was designated as the first Special Economic Zone in China in the late 1970s. However, the speed of urban expansion in Shenzhen became considerably lower than Guangzhou from 2005 to 2015, subject to physical conditions and a series of urban land use policies. Both cities showed a generally similar dynamics of urban growth forms with leapfrogging as the predominant type of urban growth at first and then edge-expansion while the contribution of infilling in Shenzhen was higher than that in Guangzhou, especially since 2005. The urbanization processes characterized by landscape and urban growth metrics revealed that a diffusion-coalescence-diffusion-coalescence process was identified for Guangzhou, while Shenzhen was generally consistent with the diffusion-coalescence urban growth hypothesis.