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Water resources are fundamental for sustaining natural ecosystems and human activities, playing a critical role in the sustainable development of the regional environment. Under the dual pressures of human activities and climate change, however, the stress on water resources has become increasingly evident, emerging as one of the greatest global risks for the next decade. In this study, by applying the water stress index, Lorenz curve, and Theil index, we explored the spatiotemporal patterns and inequality distribution characteristics of water resource stress across two scales: catchment and basin. Additionally, we used partial least squares regression to identify the key factors influencing water resource stress. The results indicated significant regional variations in water stress across China during 2002 to 2020. At the catchment scale, areas with a water stress index greater than 0.4 were distributed in the eastern, northeastern and northwestern regions. While at the basin scale, a north–south pattern emerged with lower stress in the south and higher stress in the north. The Haihe and Huaihe river basins exhibited the highest water stress. The Lorenz curve deviated significantly from the line of absolute equality, indicating a high degree of inequality in regional water resource stress. The Theil index increased from 1.26 to 1.50, showing a slight upward trend in inequality. Analysis of the driving factors revealed that the Yellow River Basin was primarily influenced by GDP and population, the Songhua River Basin was affected by population and urban land use, and the Southwest River Basin is driven mainly by vegetation cover. Overall, precipitation was the most critical driver affecting water stress, predominantly exerting a negative influence. This study provides a theoretical basis for alleviating regional water stress and offers valuable insights for the scientific planning and management of water resources.

Regional inequality significantly influences sustainable development and human well-being. In China, there exists pronounced regional disparities in economic and digital advancements; however, scant research delves into the interplay between them. By analyzing the economic development and digitalization gaps at regional and city levels in China, extending the original Cobb-Douglas production function, this study aims to evaluate the impact of digitalization on China’s regional inequality using seemingly unrelated regression. The results indicate a greater emphasis on digital inequality compared to economic disparity, with variable coefficients of 0.59 for GDP per capita and 0.92 for the digitalization index over the past four years. However, GDP per capita demonstrates higher spatial concentration than digitalization. Notably, both disparities have shown a gradual reduction in recent years. The southeastern region of the Hu Huanyong Line exhibits superior levels and rates of economic and digital advancement in contrast to the northwestern region. While digitalization propels economic growth, it yields a nuanced impact on achieving balanced regional development, encompassing both positive and negative facets. Our study highlights that the marginal utility of advancing digitalization is more pronounced in less developed regions, but only if the government invests in the digital infrastructure and education in these areas. This study’s methodology can be utilized for subsequent research, and our findings hold the potential to the government’s regional investment and policy-making.

Approximately 35 % of Chinese cities are situated in mountainous areas, where rapid urban expansion on slopes has led to the degradation of urban ecosystem health, marked by the loss of natural landscapes, diminished resilience, and reduced ecosystem services. However, the impact of vertical urban growth on ecosystem health, especially in terms of temporal dynamics, distribution, and underlying mechanisms, remains poorly understood. Chongqing, a typical mountainous metropolis, was selected to investigate these impacts over the past two decades. By integrating the slope spectrum (SS), climbing index (CI) of built-up land, and ecosystem health index (EHI), we explored how urban expansion has affected the EHI. Additionally, we developed a method for identifying the expansion advantage slope range (EASR), which can track dynamic slope-climbing urban expansion. Our findings revealed that the built-up land expansion in Chongqing was primarily concentrated in the central areas of the western region. From 2000 to 2010, this expansion occurred primarily in urban built-up areas and shifted to other built-up areas between 2010 and 2020. Although the Climbing Index was −0.11, the EASR results indicated an increasingly significant slope-climbing trend, with slopes of built-up land increasing from [1.17, 8.25] to [1.42, 8.48]. Notably, when expansion occurs on slopes exceeding 12°, the decline in the EHI becomes significantly more pronounced, with the impact coefficient rising from 0.201 to 0.447. This study reveals the fundamental relationship between slope-climbing urban expansion and ecosystems, providing valuable insights for urban planning and sustainable development in mountainous regions.

Understanding the relationship between urbanization and vegetation is essential for sustainable urban development. Over the last few decades, China has experienced rapid and dramatic urbanization along with impressive land transformations. However, the dynamic relationship between urban expansion and vegetation cover lacks enough understanding. We proposed an urbanization-vegetation cover coordination index (UVCI) by combining the physical boundaries of cities at 10-year intervals and the 250 m vegetation index, and measured the conflict or coordination relationships between urbanization and vegetation cover for 338 cities in China from 1990 to 2018. The results show that China has experienced a process of rapid, large-scale, but uneven urban expansion over the past 30 years, with urban areas expanding by approximately 556 %. Urbanization has made China’s urban areas less green, yet vegetation cover changes vary between newly developed and older urban areas. There is a substantial tendency for vegetation degradation in the newly urbanized areas, whereas vegetation cover has generally improved in the older urban areas. The vegetation in non-urban areas has been showing a noticeable greening trend after 2010, with NDVI maintaining an annual growth rate of 0.89 %. The relationship between urbanization and urban vegetation cover in China is becoming increasingly coordinated. The proportion of conflict cities decreased from 93 % in 1990–2000 to 15 % in 2010–2018. The spatial heterogeneity of the UVCI is apparent, with northern Chinese cities having achieved a largely coordinated urban-vegetation relationship, while most southern cities still face challenges. The methodology of this study can be used as a reference for subsequent research, and the findings can help shape government policies that will support green and sustainable urban development in China.

The Tibetan Plateau (TP) is undergoing rapid urbanization. To improve urban sustainability and construct ecological security barriers, it is essential to quantify the spatial patterns of urbanization level on the TP, but the existing studies on the topic have been limited by the lack of socioeconomic data. This study aims to quantify the urbanization level on the TP in 2018 with Luojia1-01 (LJ1-01) high-resolution nighttime light (NTL) data. Specifically, the compounded night light index is used to quantify spatial patterns of urbanization level at multiple scales. The results showed that the TP had a low overall urbanization level with a large internal difference. The urbanization level in the northeast, southeast and south of the TP was relatively high, forming three hotspots centered in Xining City, Lhasa City and Shangri-La City, while the urbanization level in the central and western regions was relatively low. The analysis of influencing factors, based on the random forest model, showed that transportation and topography were the main factors affecting the TP's spatial patterns of urbanization level. The comparison analysis with socioeconomic statistics and traditional NTL data showed that LJ1-01 NTL data can be used to more effectively quantify the urbanization level since it is more advantageous for reflecting the spatial extent of urban land and describing the spatial structure of socioeconomic activities within urban areas. These advantages are attributed to the high spatial resolution of the data, appropriate imaging time and unaffected by saturation phenomena. Thus, the proposed LJ1-01 NTL-based urbanization level measurement method has the potential for wide applications around the world, especially in less-developed regions lacking statistical data. Using this method, we refined the measurement of the TP's urbanization level in 2018 for multiple scales including the region, basin, prefecture and county levels, which provides basic information for the further urban sustainability research on the TP.

Urbanization is one of the most consequential human activities on earth. The contradictions between urbanization and the eco-environment are particularly prominent in urban agglomerations with high industrial concentrations. Based on the Environmental Kuznets Curve (EKC) theory, we propose the hypothesis of the Urbanization-EKC (UEKC), which states that in the process of urbanization, eco-environmental quality first deteriorates and then improves, following a “U” trend. Taking 19 Chinese urban agglomerations as empirical cases, this paper analyzed the multi-dimensional coupling curves between urbanization and the eco-environment. The results show that the coupling curves between urbanization and the eco-environment are heterogeneous, as a result of differences among urban agglomerations and various eco-environmental indicators. In five mega-urban agglomerations, we found that the coupled curve of urbanization and eco-environmental quality index (EQI) is a compound function containing logarithm and quadratic terms, following the “U” curve shape of “quick down, slow up”; the turning point of EQI improvement was found at an urbanization rate of 47%. The empirical results validate that the UEKC hypothesis is tenable for developed urban agglomerations. This study provides a methodological reference for researching the evolutionary relationship between urbanization and the eco-environment and provides decision support for a more harmonious development of humans and nature in China's urban agglomerations.