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. Plain Language Summary: Restored mangrove ecosystems have great potential to mitigate climate change and expand natural carbon sinks. They have climate benefits by sequestering atmospheric carbon dioxide, but these benefits could be offset by methane emissions and albedo changes during mangrove restoration processes. Currently, long‐term measurements of these carbon fluxes and albedo in mangrove restoration are lacking. Based on 3‐year flux tower measurements, we examined these fluxes in 8‐year restored mangrove wetlands, located in the estuary of the Aojiang River in southeastern China. The mangrove restoration acted as a carbon dioxide sink and a methane source, and the albedo of the ecosystem exhibited slight variations of 0.11–0.13. The global warming potentials of these carbon fluxes and albedo were calculated to evaluate the climatic effect of mangrove restoration. The results showed that the cooling effect of carbon dioxide uptake was dominant in the restored mangrove ecosystem, partially offset by positive radiative forcing from methane emissions and albedo changes. Mangrove restoration resulted in a net cooling contribution to the climate, despite only 8 years of restoration. Key Points: Mangrove restoration acted as a CO2 sink and a CH4 source from 2020 to 2022Integrated GWPs of CO2, CH4, and albedo showed a net cooling effect in restored mangroves and were mainly driven by CO2 uptakeRandom forest algorithm showed that PAR was the most important driver of the integrated GWPs in the restored mangrove ecosystem [ABSTRACT FROM AUTHOR]