Global Warming Potentials of CO₂ Uptake, CH₄ Emissions, and Albedo Changes in a Restored Mangrove Ecosystem

Restoration of mangrove forests has garnered increasing global prominence as a nature-based solution for carbon (C) sequestration. However, it was unclear whether the radiation forcing induced by methane (CH₄) emissions and albedo changes during mangrove restoration processes can offset the cooling effect resulting from the net carbon dioxide (CO₂) uptake. In this study, we measured the CO₂, CH₄, and albedo during 2020–2022 using an open-path eddy covariance system in an 8-year restored mangrove ecosystem afforested in Zhejiang Province, China. Their integrated global warming potentials (GWPs) were calculated to assess the climatic impact of mangrove restoration. The results showed that the restored mangroves functioned as a CO₂ sink and a CH₄ source, with annual values of −656.75 to −465.41 and 5.54 to 9.07 g C m⁻² yr⁻¹, respectively. The albedo varied slightly with a range of 0.11–0.13. The integrated GWPs of CO₂, CH₄, and albedo were −1,354.00 and −1,875.70 g CO₂-eq m⁻² yr⁻¹ over the 20- and 100-year time horizons, respectively. The negative values indicated that the mangrove restoration had a net cooling effect, mainly due to CO₂ uptake. The warming effects caused by CH₄ emissions and albedo changes had the potential to partially offset CO₂ uptake by 12.55%–36.51% and 0.08%–0.42%, respectively. Random forest analysis showed that photosynthetically active radiation (PAR) was the dominant driver on integrated GWPs with feature importance values of 0.34. Our results revealed that the cooling benefit of 8-year restored mangroves remained significant, even when it was partially offset by CH₄ emissions and albedo changes.