Quantitative analysis for ecological rivers to achieve carbon neutrality in the water network area of south China

In the context of escalating global climate change, achieving carbon neutrality has become a shared objective for the international community. However, current research on carbon neutrality mechanisms in ecological river engineering projects is limited, and systematic quantification of their carbon emissions and sinks is still lacking. This study used life cycle assessment, combining carbon emission coefficients with i-Tree Eco simulations to evaluate emissions from three typical river projects, assess native trees' carbon sequestration, and estimate neutrality timelines under various planting scenarios. Results indicated that ecological concrete revetment (T1) had the highest carbon emissions at 127,740.65 kg CO 2 e for the 1350-m river channel in Yizheng, China, followed by the geotextile gabion bag revetment (T2) at 75,058.62 kg CO 2 e and the wooden pile fence revetment (T3) at 1640.06 kg CO 2 e. Concrete accounted for 15–45 % of T1's emissions, and geotextile gabions contributed 27–67 % of T2's, confirming these construction materials as primary factors. Regarding carbon sequestration benefits, results using the i-Tree Eco model showed that Triadica , Magnolia denudata , and Cinnamomum camphora performed optimally, with gross carbon sequestration rates of 136.51 kg CO 2 e/yr, 134.00 kg CO 2 e/yr, and 91.78 kg CO 2 e/yr, respectively. For planting configurations, both the double-row arrangement of Triadica ( with spacing configurations of 3–5 m × 3 m) and the mixed planting of Magnolia denudata with Triadica ( with spacing configurations of 4–5 m × 3 m) demonstrated optimal carbon sequestration performance. To achieve carbon neutrality with trees, T1 required approximately 8–10 years, T2 needed 5–6 years, and T3 required one year. These findings offer significant implications for achieving carbon neutrality objectives in hydraulic engineering systems. However, it should be noted that the conclusions are derived from conditions specific to sandy loam soil in Yizheng City and a northern subtropical climate. Their applicability to other regions necessitates further validation through localized tree species and site-specific conditions.