Fig. 3: Study area.

The study area includes the five major urban agglomerations in China. a Beijing–Tianjin–Hebei. b Yangtze River Delta. c Pearl River Delta. d Middle reaches of the Yangtze River. e Chengdu–Chongqing.
The study area includes the five major urban agglomerations in China. a Beijing–Tianjin–Hebei. b Yangtze River Delta. c Pearl River Delta. d Middle reaches of the Yangtze River. e Chengdu–Chongqing.