The influence mechanism of supporting cities' development on the spatial expansion of economic development zones: Evidence from China's coast.

A sustainable economy through the rational spatial expansion of coastal areas is an increasingly essential global topic. This paper aims to explore the mechanism by which supporting cities influence the spatial expansion of economic development zones (EDZs) in 264 coastal EDZs of China during 1995–2020. Meanwhile, the effects of variations in the distance between supporting cities and coastal EDZs and different city scales are considered. The results provide new explanations for realizing the sustainable development of the coastal economy by planning EDZs at a suitable location from the supporting city. The supporting cities' economic strength can significantly contribute to the spatial expansion of coastal EDZs. The influence shows a distance decay law when the distance is less than 47.692 km, between 47.692 and 58.039 km, and greater than 58.039 km, with impact coefficients of 0.479, 0.393, and 0.212, respectively. The average spatial scale of coastal EDZs varies in an "inverted U–shape" with increasing distance. The average spatial scale of the urban general radiation type (47.692 km ≤ distance <58.039 km) is the largest. Supporting cities' scale affects the economic radiation range of supporting cities. The results suggest three implications for the future development of coastal EDZs. 1) Building the EDZ while incorporating practical development needs; 2) Scientifically planning the spatial layout of EDZs; 3) The synergistic development of supporting cities, transportation hubs, and EDZs. [Display omitted] • Supporting cities can promote coastal economic development zones' expansion. • The contribution of supporting cities to zone expansion shows a distance decay law. • The average spatial scale of coastal zones shows an "inverted U-shaped" change. • Supporting cities scale affects the economic radiation range by supporting cities. [ABSTRACT FROM AUTHOR]