Carbon Sequestration in Restored Tidal and Non-tidal Managed Wetlands in California's San Francisco Bay-Delta
Abstract
Wetland restoration has been identified as an effective action to increase future carbon (C) sequestration that, in combination with other conservation and management actions, could contribute to hold global warming to below 2 °C. The reversal of land subsidence, restoration of ecological integrity or the protection of aquatic resources are goals of wetland restoration that could be implemented alongside the purpose of maximizing C sequestration. How wetlands are restored and managed can make a big impact in the net wetland ecosystem C balance and the resulting net radiative forcing, as wetlands can also be large sources of methane (CH4). Here, we quantify the vertical fluxes of carbon and greenhouse gas emissions in a set of restored fresh and brackish non-tidal wetlands and a tidal euhaline wetland in the San Francisco Bay-Delta estuary. We combine the use of high-frequency Eddy Covariance atmospheric flux measurements with 210Pb-derived sedimentary C burial rates to quantify the C sequestration efficiency in restored tidal versus non-tidal wetland soils and the resulting net biogeochemical cooling effect. Results show that restored non-tidal wetlands were the most efficient in sequestering C in situ, with burial rates (260 ± 20 and 330 ± 20 g C m-2 yr-1) as high as their net C uptake rates from the atmosphere (-250 ± 80 and -360 ± 100 g C m-2 yr-1). From a radiative forcing perspective, however, the restored tidal wetland had the strongest climate cooling effect (with a min. value of -90 ± 30 g CO2e m-2 yr-1), despite its lower C burial rates over decadal timescales (33 ± 3 g C m-2 yr-1) that accounted for a ~ 10% of its atmospheric C uptake (-433 ± 44 g C m-2 yr-1). The extraordinary C sequestration efficiency of the restored non-tidal wetlands comes at the cost of high CH4 emissions (40 ± 6 g C-CH4 m-2 yr-1), which preclude them to begin accruing greenhouse gas benefits until at least a half century after restoration. From this work we aim to provide valuable information on how to restore and manage wetlands to maximize carbon uptake and minimize greenhouse gas emissions.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB048.0004A
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0442 Estuarine and nearshore processes;
- BIOGEOSCIENCES;
- 0469 Nitrogen cycling;
- BIOGEOSCIENCES