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Abstract Coastal wetlands play a vital role in the global carbon cycle and are under pressure from multiple anthropogenic influences. Altered hydrology and land use change increase susceptibility of wetlands to sea‐level rise, saltwater intrusion, tidal flood events, and storm surges. Flooding from perigean spring tides and storm surges rapidly inundates coastal wetlands with saline waters, quickly surpassing vegetation tolerances, leading to shifts in soil microbial respiration, peat collapse, and plant mortality, followed by establishment of salt‐tolerant vegetation. The Southeast Saline Everglades (SESE) is facing many of these pressures, making it a model system to examine the impacts of ecosystem state transitions and their carbon dynamics. Saltwater flooding from Hurricane Irma (2017) initiated a transitional state, where less salt‐tolerant vegetation (e.g.,Cladium jamaicense) is declining, allowing halophytic species such asRhizophora mangleto colonize, altering the ecosystem's biogeochemistry. We utilized eddy covariance techniques in the SESE to measure ecosystem fluxes of CO2and CH4in an area that is transitioning to an alternative state. The landward expansion of mangroves is increasing leaf area, leading to greater physiological activity and higher biomass. Our site was presented initially as a small C source (47.0 g C m−2) in 2020, and by 2022 was a sink (−84.24 g C m−2), with annual greenhouse carbon balance ranging from −0.04 to 0.18. Net radiative forcing ranged from 2.04 to 2.27 W m−2 d−1. As the mangrove landward margin expands, this may lead the area to become a greater carbon sink and a potential offset to increasing atmospheric CO2concentrations.
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This content will become publicly available on February 24, 2027
Compounded effects on wetland greenhouse gas fluxes from climate change and water management along a saline to freshwater gradient
Saline and freshwater wetlands store large amounts of carbon, which has driven interest in their role as nature-based climate solutions. Because these ecosystems can be both sinks and sources of carbon to the atmosphere as environmental conditions and human influence change, the net climate mitigation potential of wetlands at regional to global scales remains uncertain. We used a data-driven approach to measure ground-based and airborne fluxes to upscale carbon dioxide (CO2) and methane (CH4) fluxes using satellite-based surface reflectances at 500-m resolution across a gradient of saline to freshwater wetlands in Southern Florida, USA. Daily time series of CO2and CH4fluxes from 2000 to 2024 integrated surface properties related to vegetation productivity, flooding, and disturbance, and captured 80% and 91% of the variability in annual fluxes of CO2and CH4, respectively. Long-term (23-y) patterns in the fluxes of CH4, CO2, and their CO2-equivalent (CO2eq) are represented as Global Warming Potential 100 (GWP100) and were shown to vary spatially with wetland management, revealing higher carbon uptake in mangroves susceptible to hurricane damage and coastal hydrology, and greater carbon emissions in freshwater sawgrass marshes where freshwater hydrology is managed for restoration. Regional net annual CO2eq uptake in coastal and freshwater wetlands increased by 18% from −7.0 ± 3.3 MMT CO2eq y−1in ~2003 to −8.4 ± 3.8 MMT CO2eq y−1in ~2020 at an uptake rate of −0.06 ± 0.01 MMT CO2eq y−2. Annually, roughly 43% of CO2uptake was offset by CH4emissions from all wetlands in the region (from 16% in mangroves to 82% in freshwater marshes).
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- PAR ID:
- 10712123
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- National Academy of Sciences
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 123
- Issue:
- 8
- ISSN:
- 0027-8424
- Subject(s) / Keyword(s):
- carbon monitoring system upscale model blue carbon teal carbon methane
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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