Spatiotemporal dynamics of carbon sources and sinks and driving mechanisms of net carbon emissions: a case study of the Yangtze River Economic Belt

The scientific quantification of regional net carbon emissions (NCE) and the elucidation of their underlying mechanisms are of great significance for advancing sustainable development. However, carbon-related research has long suffered from a separation between sources and sinks, and there remains a lack of systematic understanding of the driving mechanisms behind NCE. Taking the Yangtze River Economic Belt (YREB) as a case study, this research quantifies carbon sinks based on net ecosystem productivity (NEP) to estimate NCE, and employs correlation analysis and partial least squares path modeling (PLS-PM) to elucidate the influencing mechanisms of NCE and its relationship with the human-environmental system (HES). The results indicate that carbon sources and NCE exhibited a clear upstream-to-downstream increasing gradient, opposite to the pattern for carbon sinks, with total NCE rising from 1188.56 Mt (2000) to 3656.60 Mt (2022) Meanwhile, carbon sources, sinks, and NCE all exhibit significant positive spatial autocorrelation (p < 0.01). Among the influencing factors, urbanization rate (UR), energy consumption per unit of GDP (UEPV), and normalized difference vegetation index (NDVI) demonstrate significant correlations (p < 0.01), though key influencing factors vary regionally, with global correlation coefficients generally increasing. From an HES perspective, social factors exert a strong positive direct effect on NCE (mean path coefficient = 0.497, p < 0.01), while ecological factors have a direct negative effect (mean path coefficient = −0.267, p < 0.05, except in 2006). In contrast, economic factors primarily produce an indirect effect (mean path coefficient = 0.163, p < 0.01). This study demonstrates that the synergistic evolution of the HES is the core mechanism underlying the spatiotemporal differentiation of NCE. It is recommended that region-specific low-carbon strategies be implemented through the coordinated regulation of social, economic, and ecological systems to achieve the dual carbon goals in the YREB.