Does the National Key Ecological Function Zones Policy Promote Leapfrog Development in Urban–Rural Integration?

Integrated urban–rural development is an inevitable requirement of regional development. Developing green industries based on rural ecological resources are important approaches to promoting urban–rural integration. The National Key Ecological Function Zones (NKEFZ) policy focuses on safeguarding national ecological security. However, whether the resulting ecological improvements can, through the realization of ecological value, provide momentum for urban–rural integration remains unclear in existing research. This study uses a sample of 284 prefecture-level cities in China from 2006 to 2023, treating the establishment of NKEFZ as a quasi-natural experiment. First, the study constructs a “Driving-constraining” bidirectional theoretical framework, and then uses the entropy weight method to measure the level of urban–rural integration, which is selected by 18 sub-indicators from the populational, spatial, and economic dimensions. Finally, a multi-period difference-in-differences (DID) model is constructed to test the impact of NKEFZ on urban–rural integration, and the transmission mechanisms and heterogeneity are explored. The results indicate the following: (1) Following the implementation of the NKEFZ policy, it shows an overall inhibitory trend on urban–rural integration, consequently slowing the progress of urban–rural integration. The inhibitory effects are particularly pronounced in spatial and economic integration dimensions, and these results are robust. (2) Constrained industrial upgrading and increased fiscal pressure on local governments are the main mechanisms behind the slowed urban–rural integration. (3) Due to differences in policy coverage and the heterogeneous characteristics of city locations, the negative effects of the policy are more pronounced in cities with a high proportion of key ecological function counties, as well as in prefecture-level cities in central and western regions. Based on these findings, it is suggested to promote high-quality urban–rural integration in eco-priority areas through pathways such as developing ecological industries, improving the ecological compensation system, and clarifying central–local collaborative governance.