Spatiotemporal Dynamics of Shrinking Cities at the County Level: Insights from NPP-VIIRS Nighttime Light Data in the Yangtze River Delta, China

Urban shrinkage represents a significant global socioeconomic challenge. In the Yangtze River Delta (YRD) region of China, rapid urban expansion coexists with city shrinkage, posing significant threats to sustainable development. While existing scholarship emphasizes global or national scales, regional dynamics remain understudied. This analysis employs Suomi National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suite (NPP-VIIRS) nighttime light data from 2014 to 2023 to analyze spatiotemporal shrinkage patterns across YRD county-level cities. It also analyzes trends of agglomeration and dispersion and assesses the influence of factors such as urban scale, function, and transportation conditions. Key findings reveal that 12.4% of cities experienced shrinkage, predominantly concentrated in Anhui Province. The shrinking cities exhibit a northwest–southeast pattern; most of these cities primarily form low–low clusters, although high–high clusters are increasing. Commercial-oriented cities constitute the majority of shrinking cities, followed by tourism-oriented cities. Smaller cities with limited functions and inadequate transportation are more prone to shrinkage. This research enhances the understanding of urban shrinkage dynamics at the county level, offering actionable pathways for sustainable development amid the accelerated urbanization of rapidly urbanizing regions such as the YRD.