Contemporary Urban Expansion in the First Fastest Growing Metropolitan Region of China: A Multicity Study in the Pearl River Delta Urban Agglomeration from 1980 to 2015

Contemporary urbanization in the Pearl River Delta (PRD) Urban Agglomeration is the epitome of China's urbanization process as the PRD is the first fastest growing metropolitan region of China. Here, we mapped and quantified the spatiotemporal dynamics of urban expansion for seven major cities in the PRD between 1980 and 2015, using remotely sensed data integrated with landscape metrics, urban growth form, and rank clocks. Results showed that rapid land urbanization occurred in all the seven cities since the execution of reform and opening up, with the annual increase rate ranging from 8.1% to 11.3% among cities, suggesting a relatively equal level of urbanization within the PRD. Socioeconomic drivers underlying urban expansion in Guangzhou, Shenzhen, and Zhuhai can be characterized as "top-down" mechanisms led by the municipal government, while those in Foshan, Jiangmen, Dongguan, and Zhongshan are "bottom-up" ones from low-level administrative organizations. The trajectory of urban expansion in Shenzhen conformed to the diffusion-coalescence urban growth hypothesis in terms of temporal evolution of landscape metrics and urban growth types. This is related to the fact that Shenzhen, the first special economic zone established by the Chinese government, was the first mover of urbanization in China and functioned under the umbrella of a robust socialist market economy relative to a highly centralized planned economy for other cities. The changes of Shenzhen in rank order in terms of both urban population and urbanization area were the largest, exemplifying its evolution from a small fishing village to a metropolis. Furthermore, we found that moving up in the rank order in terms of land use efficiency of wealth creation over time for all cities was accompanied with rank clocking up of population per area (crowd). How to balance trade-offs between the benefits and costs of urbanization is the challenge faced by the urban agglomeration.