Coastal Wetland Restoration Effects on Carbon Dynamics: A Groundwater Perspective

Abstract Coastal wetlands are critical components of the global carbon cycle, yet many have been degraded by drainage and land‐use changes, releasing stored carbon and exacerbating climate change. Interest in wetland restoration is increasing globally due to their carbon storage capacity, ecosystem values, and biodiversity co‐benefits. This is further supported by the United Nations' declaration that 2021–2030 is the “ Decade on Ecosystem Restoration .” Various techniques have been applied to achieve ecological wetland restoration. However, additional opportunities should be explored to extend the co‐benefits of restoration beyond ecological aspects. For these restoration co‐benefits to be fully optimized, the science of wetland functions and processes must be understood and quantified. Groundwater plays a crucial role in wetland carbon transport, storage, and transformation. However, its processes are often overlooked or poorly quantified. This paper (a) provides the current state of knowledge on subsurface hydrology and biogeochemical processes in wetlands, (b) describes how the hydrologic restoration of wetlands may affect the physical and chemical processes within wetlands, and (c) discusses how restoration can alter wetland function, with a specific focus on carbon and greenhouse gas dynamics. The paper highlights the necessity for a holistic, interdisciplinary approach to wetland restoration research, considering the interplay of hydrological, biogeochemical, and climatic factors to optimize carbon sequestration and ensure the long‐term success of restoration projects.