The intricate interplay between water resources, land resources, energy systems, and carbon emissions has emerged as a prominent discourse in academic research. Nonetheless, there remains a dearth of comprehensive research dedicated to fostering environmentally friendly and low-carbon development through systematic integration and coordination efforts. This study aimed to fill this gap by integrating the coupling mechanism of the Water-Land-Energy-Carbon (WLEC) system, thereby constructing an evaluation index framework that assesses coordinated developments in Northwest China’s WLEC system. It scrutinizes the security levels within the Water-Land-Energy (WLE) subsystem while conducting quantitative analyses on the degrees of coupling coordination within the WLEC systems, alongside their associated hindering factors. The preliminary findings were as follows: Firstly, the safety development within the WLE system demonstrates a positive trend across Northwest China, with notable advancements primarily observed in the Qinghai and Gansu provinces. In 2021, all five Northwestern provinces exhibited moderate levels of safe development, except for the Qinghai province, which transitioned from moderate to robust. Secondly, the coupling coordination degree of the WLEC system across the five provinces has consistently illustrated an upward trajectory over the years. However, as of 2021, the system remains in a state characterized by marginal disorder. Notably, the Qinghai and Gansu provinces have shown particularly encouraging upward trends, with the Shaanxi province also making notable progress. Conversely, Xinjiang has declined since 2017 due to negative interactions between the subsystems of water, soil, energy, and carbon emissions. Thirdly, spatial variations exist in the distribution patterns between the provinces regarding the influence of obstructing factors on indicators related to coupled coordinated development, such as per capita arable land area, per capita energy consumption, per capita carbon emissions, per capita construction land area, and the proportion of groundwater water in the total amount of water supply, which demonstrated an increasing trend. These findings carry significant practical implications for actively and steadily promoting carbon peaking and carbon neutrality in Northwest China.

Methane (CH₄), the second-largest global greenhouse gas and a key driver of tropospheric ozone formation, critically influences climate change and air quality. As the world’s largest CH₄ emitter, China must develop targeted mitigation strategies to support its carbon peak and neutrality goals while reducing ozone pollution. Here, we analyzed the spatiotemporal evolution of provincial CH₄ emissions in China from 2000 to 2023 using spatial autocorrelation, hotspot detection, trend analysis, and K-means clustering. Our results revealed a triphasic emission trajectory—rapid growth followed by stabilization and a recent resurgence—with all provinces except Tibet showing increasing trends. The energy sector emerged as the primary contributor, particularly in Inner Mongolia, Shanxi, and Shaanxi, whereas agricultural emissions dominated in pastoral regions, such as Inner Mongolia and Sichuan, and rice-growing areas, such as Hunan and Hubei. Coastal provinces, including Shandong, Jiangsu, and Guangdong, exhibited waste disposal as their predominant CH₄ source. Based on these patterns, we classified the emission zones into four distinct typologies: coal-dominant, waste-dominant, oil-agriculture composite, and multifactorial systems, proposing tailored mitigation frameworks that integrate CH₄ and ozone co-reduction. This study provides a spatially resolved foundation for synergistic climate and air quality governance in China.