Unlocking the potential of collaborative innovation to narrow the inter-city urban land green use efficiency gap: Empirical study on 19 urban agglomerations in China

Urban land green use efficiency (ULGUE) is a vital component of urban sustainability and resilience. However, imbalanced ULGUE can undermine these goals. Collaborative innovation has emerged as a promising approach to address this pressing challenge, yet its impact on the inter-city ULGUE gap remains largely underexplored. This paper aims to fill this gap by proposing a theoretical framework of collaborative innovation affecting the ULGUE gap. To validate this framework, we devised a comprehensive evaluation index of the ULGUE gap based on the core-periphery theory and employed a system generalized method of moments model (Sys-GMM) and a threshold model to analyze a sample of 19 urban agglomerations in China. Our study uncovers several vital insights. Collaborative innovation significantly diminishes the ULGUE gap within urban agglomerations, exhibiting a double-threshold effect in this relationship. The threshold values are 1.5821 and 2.0246, respectively, allowing us to categorize urban agglomerations into three stages based on their collaborative innovation levels. Besides, government intervention can mitigate the effects of collaborative innovation on the inter-city ULGUE gap, potentially delaying the trend of the narrowing ULGUE gap. These findings imply that the phased characteristics of collaborative innovation should be considered when designing policies for urban development and sustainability.