The spatio-temporal characterization of urban expansion of three urban agglomerations in China

Abstract

The study selects three most representative megacity regions in China: Beijing-Tianjin-Hebei, Yangtze River Delta and Guangdong-Hong Kong-Macao greater bay area to explore the spatio-temporal characteristics of the development of urban agglomerations in China. To do so, we employ the built-up area data from 1990 to 2020, and calculate three types of urban expansion indicators such as urban expansion dynamics, landscape expansion index, and urban ranking clock theory. The comparison of these indicators in the past three decades is further conducted. Moreover, the correlation analysis helps to find the driving factors of the growth of the three major urban agglomerations. To be specific, (1) The Beijing-Tianjin- Hebei urban agglomeration has entered a period of rapid urbanization, the Yangtze River Delta urban agglomeration has entered a period of steady expansion, and the Guangdong-Hong Kong-Macao urban agglomeration has entered a period of slow maturation of expansion. (2) The expansion patterns of the three major urban agglomerations are mainly marginal expansions, while the enclave expansions are gradually decreasing; the expansion pattern is starting to move from diffusion to agglomeration, but the degree of agglomeration is still low, in the meantime, the degree of agglomeration in the Beijing- Tianjin-Hebei urban agglomeration is higher than that in the Guangdong-Hong Kong-Macao and Yangtze River Delta urban agglomerations. (3) The changes of city order scale of Beijing-Tianjin-Hebei city cluster and Guangdong-Hong Kong-Macao city cluster show a decreasing trend, while the changes of city order scale of Yangtze River Delta city cluster show an obvious increasing trend. (4) Socio-economic factors are significantly and positively correlated with urban expansion, among which the increase of the proportion of tertiary industry in GDP is the most relevant to urban expansion, while factors such as policy and geographic location are also important factors .