Carbon reduction and water resource trade-offs in the digital-green synergistic transformation

• Digital-Green Synergistic Transformation (DGST) exhibits an inverted U-shaped effect on carbon emissions, revealing the necessity of adaptive policies. • DGST induces an inverted U-shaped carbon–water trade-off, with initial conflicts most evident in regions east of the China and in water-scarce areas. • Significant spatial spillovers of DGST affect carbon emissions and trade-offs, emphasizing coordinated cross-regional governance. The Digital-green synergistic transformation (DGST) constitutes a critical pathway for addressing climate change and advancing sustainable development. This paper examines the impact of DGST on carbon emissions and its associated environmental trade-offs, drawing on panel data from 280 Chinese cities. The results reveal a significant nonlinear relationship between DGST and carbon emissions, characterized by an inverted U-shaped pattern. This effect is more pronounced in regions located east of the China and in areas with abundant water resources. From a coupled resource system perspective, the analysis further identifies a carbon–water trade-off during the early stages of transformation, wherein carbon reductions are accompanied by increased water consumption. This trade-off is particularly evident in cities east of the China and in water-stressed regions. Spatial econometric analysis reveals significant spatial autocorrelation in carbon emissions, suggesting that DGST is associated with spatial spillover effects on carbon emissions and related trade-offs across regions. This paper contributes to the theoretical understanding of the mechanisms underlying carbon mitigation within the context of DGST and provides empirical insights to inform multi-objective environmental governance and policy formulation.