Promoting the integrated development of the Yangtze River Delta (YRD) is a major national strategy with an aim to achieve the "Two Centenary Goals". This paper firstly analyzed the new connotation of the integrated development of the YRD after China's entering a new development stage, and proposed the "four more" connotations of integrated high-quality development of the YRD, namely, integration with higher strategic positioning, integration with higher efficiency and level, integration with more coordination, and integration with better spatial form. Then the main actions and achievements of the integrated development of the YRD since it was elevated to a national strategy were reviewed and summarized. To study the new concept of high-quality development, an evaluation index system reflecting the five new development concepts of innovation, coordination, green, openness and sharing was constructed, and the state of integrated high-quality development of the YRD from 2018 to 2020 was assessed. Finally, against the new requirements of integrated high-quality development, relevant countermeasures and paths for specific areas were proposed in response to the current issues, which provides a reference for decision making to promote integrated higher-quality development of the YRD.

Inefficient and idle industrial land governance, also known as "brownfield" redevelopment, is one of the important contents of urban renewal in the post-industrialization period in the Western countries. Shanghai became the pilot city in China to fully implement the reduction governance of inefficient industrial land in 2013, taking the lead in launching a new high-quality development path from incremental expansion of land resources to the reduction of inefficient land. In 2015, China's 13th Five-Year Plan (2016-2020) officially made inefficient construction land reduction governance a national strategy. Beijing, Guangzhou and cities in the Yangtze River Delta (YRD) have begun to explore this practice. Under the background of the YRD's transition from incremental expansion to stock renewal, it is of great significance to explore inefficient industrial land reduction governance, improve the efficiency of land use to optimize the pattern of land resource utilization, and promote industrial upgrading and high-quality urban development. This paper analyzes the characteristics of the complex system of inefficient industrial land governance, constructs a policy process analysis framework of "Situation-Structure-Implementation-Outcome", and takes the mega-city of Shanghai as an example to reveal the action process and operation mechanism of reduction using Grounded Theory Methodology. The results show that: (1) The reduction of inefficient industrial land is characterized by planning restriction, public interests and rural embeddedness. The complex adaptive system of "outer edge-inter core" is composed of external environment, land use effect, principle role and reduction governance. (2) The resource, environment, development pressure in a macro perspective, as well as land use effect in a micro perspective, under the rigid ceiling constraint of "construction land", are the external scenarios of reduction. The lack of governance capacity of endogenous subjects and the active intervention of exogenous subjects based on public interests jointly constitute a governance structure based on value sharing. Rigid policy, incentive policy and supportive policy form a "triple complementarity" system to promote collective action. The results show the coordination between high-quality urban development and resource reallocation. Balancing ecological protection and economic development and relieving the short-term pressure of reduction will become the focus and a tough task for Shanghai to continue the governance of reduction. This research provides experiences and case study for other cities in the YRD region in inefficient industrial land reduction.