Farmland use transition (FUT) not only reshapes agricultural production systems but also significantly impacts cross-regional carbon sink transfers in the grain trade. However, comprehensive studies exploring connections between FUT and grain carbon sink transfer (GCST) are limited. We constructed an indicator system and transformation framework for FUT by considering dominant and recessive dimensions. Moreover, we estimate GCST based on grain supply–demand balance and fixed carbon coefficients. Fixed effects and threshold models are employed to identify both linear and nonlinear relationships between FUT and GCST. Results show that FUT significantly reshapes carbon sink flows. In terms of dominant FUT indicators, cultivation land rate (CLR) and grain planting area proportion (GPAP) positively drive GCST by expanding the carbon sink supply and exporting ecological services. Regarding recessive FUT indicators, both grain yield per unit area (GYield) and pesticide-fertilizer intensity (PFI) promote GCST, highlighting the role of efficiency and inputs, while rural per capita disposable income (RPCDI) suppresses GCST due to agricultural marginalization. A grain yield threshold of 2.092 t/ha is identified. Below this value, FUT exerts substantial positive effects on GCST. Above it, the effects weaken. This study explains the relationship between FUT and ecosystem carbon sinks, providing a scientific basis for advancing green agriculture in karst mountainous areas.

The idleness of rural residential lands (RRLs) has become a universal governance challenge amid global urbanization. In China, revitalizing these dormant assets is particularly critical yet constrained by its unique collective ownership system and a state-dominated institutional environment. To systematically assess the current governance logic, this study transcends traditional single-dimension evaluations by constructing a three-dimensional analytical framework of “policy path–policy tool–policy effectiveness.” Employing the content analysis method, the PMC-Index model, and the coupling coordination degree model, we quantitatively evaluated 22 central and local RRL revitalization policies issued between 2019 and 2024. The results indicate that (1) The policy path forms a logical “goal–resource–process–guarantee” linkage; however, it lacks regional adaptability and exhibits a characteristic of “strong administration but weak participation.” (2) Policy tools present a structural contradiction: supply-oriented tools are overused, demand-oriented tools lack adequate market orientation, and environmental tools rely heavily on rigid regulatory constraints, reflecting a systemic tendency to “emphasize control over guidance.” (3) Despite these structural imbalances, the overall design quality and effectiveness of the policies remain relatively high. There is a strong coupling coordination among the three dimensions, with the richness of the path design acting as the primary driver of policy effectiveness. To optimize future governance, policymakers should establish a dynamic calibration mechanism for policy instruments and construct a hierarchical, differentiated policy path. These findings not only clarify China’s institutional reform trajectory but also provide transferable empirical insights for rural land governance globally.

Narrowing the urban–rural divide is a critical challenge for developing countries and a core concern of the United Nations 2030 Agenda for Sustainable Development (particularly Sustainable Development Goals (SDGs) 10 and 11). To this end, China has launched pilot reforms of the rural homestead system to optimize the allocation of land resources, revitalize idle rural construction land, and advance the sustainable development of urban–rural integration (URI). Treating the rural homestead system reform pilots as a quasi-natural experiment, this study employs the difference-in-differences (DID) method based on panel data of 1380 counties (districts and county-level cities) in China from 2010 to 2021 to identify the reform’s impacts on county-level URI (an inverse measure of the urban–rural divide) and its transmission channels. The results show that the rural homestead system reform increases the URI index of pilot counties by an average of 0.102 units relative to non-pilot counties (cluster-robust standard error = 0.046, significant at the 5% level). This finding remains robust after a battery of tests including placebo tests, winsorization, lagged treatment and the exclusion of potentially affected controls. The policy effect exhibits obvious heterogeneity and is more pronounced in regions with higher baseline URI, municipal districts, county-level cities, as well as eastern and northeastern China. Mechanism tests further indicate that the reform functions through three channels: optimizing the allocation of urban and rural labor, accelerating the flow of capital factors, and promoting industrial structure upgrading. Specifically, labor, capital and industrial structure indicators at the county level rise significantly by approximately 1.5%, 3.2%, and 0.8%, respectively (coefficients equal to 0.0150, 0.0314, and 0.0076, all significant at the 1% level). The URI evaluation index constructed in this paper covers five dimensions: population, space, economy, society and ecology. Incorporating the ecological dimension enables the measurement of URI to reflect the multiple goals of sustainable development. The findings provide policy implications for deepening rural land system reform and advancing high-quality URI.