Optimising the allocation of population, land, and capital production resources is crucial for promoting an efficient urbanisation and solving the urban land financial problem. This study uses a panel threshold model to identify the response boundary of urban construction land use efficiency to government debt level for 51 postfinancial crisis Chinese coastal cities. The results indicate that the threshold of economic development level and provincial gross domestic product (per capita gross domestic product: pgdp) are 2.67 and 5.17, respectively. In cities with relatively backward economic development, an expansion of the government debt scale hinders the improvement of the utilisation efficiency of construction land. Also, the threshold value of the government’s accumulated debt level threshold (sd) is 15.83%. When cities fall below the government accumulated debt level threshold (sd < 15.83%), the new debt level has a positive effect on the utilisation efficiency of construction land. When sd > 15.83%, the new debt level impedes the improvement of the utilisation efficiency of construction land. Local governments should reduce their dependence on land finance in cities with high cumulative debt ratios, especially those with negative responses to both thresholds (pgdp and sd thresholds). This study’s findings can provide a reference for a sustainable promotion of new urbanisation in both China and in other countries to avoid the risk of land urbanisation.

Land use efficiency (LUE) serves as a crucial nexus between economic development and sustainable resource management, directly influencing urban production–consumption systems. While economic development stages (EDSs) reflect a region’s environmental carrying capacity and profoundly affect LUE, the specific mechanisms governing this relationship remain unclear. In this study, we combined multi-source data to portray the spatiotemporal patterns of EDSs and LUE in 276 Chinese cities from 1995 to 2020, and we identified the nonlinear effects of EDSs on LUE. Based on the fine-scale LUE, it is confirmed that the older the age of urban land generation, the higher the LUE, laying a theoretical foundation for subsequent research. Simultaneously, the EDS continues to be upgraded, with approximately 70% of cities reaching the post-industrialization stage or higher by 2020. The results of partial dependency plots (PDPs) revealed that the EDS has a positive impact on LUE. From the perspective of different urban scales, the higher the EDSs of supercities, type I large cities, type II large cities, and type II small cities, the greater the positive impact on LUE, whereas the impact patterns at other urban scales follow an inverted U-shape. These findings carry important implications for sustainable spatial development, particularly in optimizing land resource allocation to assist the shift to more efficient production systems and responsible consumption patterns.

An in-depth analysis of land use dynamics during the evolution of regional urban systems is crucial for understanding developmental trajectories and promoting coordinated urban growth. This study adopts a land-use perspective, examining the expansion of urban construction land while identifying its source areas. By integrating Zipf’s law and using urban construction land area as an indicator of urban scale, this research analyzes transformations within the urban system. The findings reveal the following: (1) The total area of urban construction land in the Yangtze River Delta has continued to expand over time, exhibiting an inverted U-shaped curve, with high concentration observed in riverine and coastal zones. (2) Cultivated land serves as the primary source for construction land, contributing on average 77.70% over the past 25 years, amounting to a conversion of 5664.51 square kilometers. Rural residential areas rank second, contributing an average of 11.90%. (3) The rank-size distribution of cities based on urban land area largely aligns with Zipf’s law, albeit with deviations at both ends. The Pareto index increased from 0.803 to 0.897, indicating a trend toward weaker dispersion and greater concentration in urban size distribution. In conclusion, future urban development should emphasize rational expansion grounded in sustainable practices, strengthen farmland protection to ensure food security, and effectively manage rural land transformation to promote efficient land use and ecological balance. These measures will support the balanced and coordinated development of large, medium, and small cities within the urban system.

Land-use change and its interaction with petrochemical accident risk are critical for sustainable coastal development. This study established a multi-source data-integrated risk assessment framework, employing fuzzy C-means clustering to stratify petrochemical accident risk into six distinct levels. The analysis revealed the relationship between these risk levels and land-use type changes. Furthermore, the Takagi–Sugeno fuzzy dynamic model was applied to evaluate potential risks at representative coastal petrochemical enterprises. The findings were as follows: (1) Risk concentrates in small-to-medium private, newly established firms, primarily as explosion accidents. (2) The highest risk occurs in Bohai Bay, followed by Jiangsu, Zhejiang, and Guangdong; national policies have reduced affected zones from 352.61 km² (2019) to 43.67 km² (2022). (3) The total potential risk zone spans 2986.21 km², with high-risk cores in Hebei, Zhejiang, and Fujian (36.52%) and medium-risk in Shandong Peninsula (32.01%). (4) Risk primarily affects farmland and construction land; urban expansion has increased affected built-up areas from 16.36% (2012) to 47.02% (2022), shifting effects from ecological to combined socio-ecological consequences. These findings provide critical theoretical support and actionable management recommendations for integrating coastal land-use planning, urban expansion control, and coordinated petrochemical risk governance.