Can the ecological transition of cropland use narrow rural-urban income inequality? Evidence from China’s Huang-Huai-Hai Region

Rural-urban income inequality (RUIE) remains a persistent challenge across many rapidly developing regions, undermining socio-economic welfare and hindering sustainable development. The ecological transition of cropland use (ETCU), a management paradigm rooted in the principles of sustainable intensification, is widely advocated to enhance agricultural sustainability. While localized case studies suggest that such practices can bolster rural incomes through improved resource efficiency or product diversification, robust empirical evidence on whether large‑scale ETCU adoption mitigates regional RUIE remains scarce, and the underlying systemic mechanisms are poorly understood. This study develops a multi-scale "cropland-agriculture-rural" framework to analyze how ETCU influences RUIE in China's intensively cultivated Huang-Huai-Hai Region. By integrating plot-scale biogeochemical modeling (PEST-DNDC), county-level panel data (2000–2020), and Structural Equation Modeling, we systematically quantify the spatiotemporal patterns and causal pathways of this transition. The results demonstrate that: (1) ETCU and RUIE exhibit spatially heterogeneous co-evolution; improvements in ETCU are not consistently associated with reduced inequality, and in some coastal counties, they even coincide with widening gaps. (2) ETCU affects RUIE primarily by restructuring agricultural multifunctionality, which serves as the core mediator. (3) The effects are highly dimension-specific. Enhancing resource-use efficiency exerts a modest yet significant direct mitigating effect on RUIE. Conversely, improvements in productivity and environmental performance exhibit no direct effect; instead, they indirectly exacerbate inequality by weakening the agricultural product supply function—which our model identifies as a strong and direct suppressor of RUIE. The economic value-added and ecological conservation functions do not exhibit significant direct equalizing effects. These findings indicate that the equity outcomes of ETCU are not automatic but depend critically on how it reshapes the multifunctional structure of agriculture. Policy interventions must therefore adopt an integrated approach that strategically guides the agricultural transition toward balanced multifunctionality, safeguards diversified production, and ensures that efficiency gains translate into broadly shared benefits for both rural and urban households.