Recent Acceleration of Wetland Accretion and Carbon Accumulation Along the U.S. East Coast

• Published in: Earth's future 2023-03, Vol.11 (3), p.n/a
• Main Authors: Weston, Nathaniel B., Rodriguez, Elise, Donnelly, Brian, Solohin, Elena, Jezycki, Kristen, Demberger, Sandra, Sutter, Lori A., Morris, James T., Neubauer, Scott C., Craft, Christopher B.
• Format: Article
• Language: English
• Subjects: Accretion; Accumulation; Carbon; Carbon sequestration; Climate change; Coastal zone; Coasts; Deposition; Global positioning systems; GPS; Low temperature; Primary production; Rivers; salt marsh; Sea level; Sea level rise; sediment; Sediment transport; Sedimentation & deposition; Sediments; Suspended sediments; Vegetation; Watersheds; wetland; Wetland soils; Wetlands
• ISSN: 2328-4277; 2328-4277
• DOI: 10.1029/2022EF003037

The long‐term stability of coastal wetlands is determined by interactions among sea level, plant primary production, sediment supply, and wetland vertical accretion. Human activities in watersheds have significantly altered sediment delivery from the landscape to the coastal ocean, with declines along much of the U.S. East Coast. Tidal wetlands in coastal systems with low sediment supply may have limited ability to keep pace with accelerating rates of sea‐level rise (SLR). Here, we show that rates of vertical accretion and carbon accumulation in nine tidal wetland systems along the U.S. East Coast from Maine to Georgia can be explained by differences in the rate of relative SLR (RSLR), the concentration of suspended sediments in the rivers draining to the coast, and temperature in the coastal region. Further, we show that rates of vertical accretion have accelerated over the past century by between 0.010 and 0.083 mm yr−2, at roughly the same pace as the acceleration of global SLR. We estimate that rates of carbon sequestration in these wetland soils have accelerated (more than doubling at several sites) along with accelerating accretion. Wetland accretion and carbon accumulation have accelerated more rapidly in coastal systems with greater relative RSLR, higher watershed sediment availability, and lower temperatures. These findings suggest that the biogeomorphic feedback processes that control accretion and carbon accumulation in these tidal wetlands have responded to accelerating RSLR, and that changes to RSLR, watershed sediment supply, and temperature interact to determine wetland vulnerability across broad geographic scales. Plain Language Summary Coastal wetlands provide critical ecosystem services but are thought to be increasingly vulnerable in the face of rising seas. Wetlands can build vertically and maintain elevation relative to sea level by forming new soil through the preservation of organic matter produced by marsh plants and the trapping of sediments delivered during tidal flooding if the rate of sea‐level rise doesn't exceed the accretion capacity. We measured rates of salt marsh vertical accretion and carbon accumulation at nine sites along the U.S. East Coast from Maine to Georgia that experience a range of local sea‐level rise and watershed sediment supplies. We found that rates of vertical accretion have accelerated over the past century in a manner very similar to the acceleration of global sea‐level rise. Our findings also indicate t