Rates and patterns of urban expansion in China's 32 major cities over the past three decades

Rates, patterns, and consequences of urban expansion are drawing increasing attention globally because of their profound impacts on socioeconomics, human life, and the environment. Horizontal comparative studies across multiple cities over large geographic regions are rare. We quantified and compared the magnitude and forms of urban expansion for China's 32 major cities, and examined the spatiotemporal evolution of urban growth and trajectory of patch structure formation. Multi-temporal Landsat data of circa 1978, 1990, 1995, 2000, 2005, and 2010, patch-based analyses, and urban growth metrics were used. These 32 major cities have experienced extensive expansion during the study period. Leapfrogging was the dominant urban expansion form, followed by edge-expansion and infilling in the early time periods. Interestingly, the fractions of infilling, edge-expansion, and leapfrogging has gradually reached a quasi-equilibrium condition with a ratio of 2:4:4 (the number) and 2:5:3 (the area) during recent years. Patch analysis suggested that these cities evolved under a nationally-consistent converged urban patch structure regardless of city size, location, and history. The dynamics of urban growth in China corresponded well with its socioeconomic and political geography and the phased implementation of various regional and national policies. Our results generally supported the continuum of diffusion-coalescence urbanization process and a spatial self-organization of urban land patches during urbanization. More studies are needed to test the generality of urban growth hypothesis and examine the universality of converged urban patch structure across regions and countries and to understand their implications to city organization, metabolism, and evolution.National Natural Science Foundation of China [31321061, 41071050]; 111 Project [B14001]SCI(E)ARTICLEsqzhao@urban.pku.edu.cn81541-15593