Urban Distribution and Evolution of the Yangtze River Economic Belt from the Perspectives of Urban Area and Night-Time Light

Research on urban development patterns and urban sprawl in the Yangtze River Economic Belt (YREB) has received wide attention. However, existing research has always made use of statistical data, which are not often available. Considering the high availability of satellite data, this study attempts to combine two satellite-acquired indexes, including urban area and night-time light, to evaluate the urban development of the YREB during 2012–2019. The methods included using growth index, rank-size law, and the Markov transition matrix, as well as constructing urban night-time light density and unbalanced index of night-time light, derived from the Gini Index. Some important patterns were revealed. Firstly, the three reaches (Upper Reaches, Middle Reaches, and Lower Reaches) in the YREB have all shown rapid growth in urban area and night-time light, and they all have increased in urban density. Secondly, from the perspective of regional disparity, the Upper Reaches have the highest growth rate of the urban area, while the Middle Reaches have the highest growth rate of night-time light; and the Upper Reaches have more urban sprawl, while the Middle Reaches have shown more compact growth. Thirdly, higher urban density is related to more balanced development across cities. Our study suggests new knowledge can be obtained by combining the two indexes for understanding urban development in the YREB.