How can urban agglomeration market integration promote urban green development: evidence from China's Yangtze River Economic Belt.

Green development of cities has been gaining attention worldwide, especially in urban agglomerations, where market integration is promoting. However, it is not clear whether the market integration in urban agglomerations is conducive to promote the green development of cities. Hence, this research aims to address this question. This research employed the data of 100 cities in China's Yangtze River Economic Belt from 2006 to 2019 and a comprehensive analytic framework including a panel threshold model to explore the impact of urban agglomeration market integration on urban green development and the nonlinear adjustment mechanism. The main findings are shown below: (1) urban agglomerations market integration was found to be significant to promote green development of the city, but there are two dimensions: the horizontal dimension and the efficiency dimension, (2) the optimal dimensions for urban agglomeration market integration to promote green development of the city were found has regional and urban heterogeneity. Therefore, it is necessary for the city to formulate differentiated green development strategies, (3) when human capital advancement and knowledge sharing intervene, urban agglomeration market integration will have a "jumping" threshold impact on green development of the city through the level path; and under the adjustment of environmental regulations and the green transformation mechanism of the industrial structure, the influence of the urban agglomeration market integration on the efficiency of urban green development presents a "U-shaped" threshold characteristic, (4) lastly, the conclusions enlighten urban agglomeration market integration and heterogeneous green development model for approaching a better performance in urban green development.