Satellite‐Based Assessment Reveals Patterns of Coastal Marsh Carbon Sequestration Along the U.S. East and Gulf Coasts

Abstract

Coastal marshes are critical blue‐carbon ecosystems, yet regional quantification of vegetation‐derived carbon burial and living biomass carbon stocks within marshes remains limited. Here, we developed a transparent, measurement‐based framework integrating Sentinel‐2 data (2019–2024), field biomass measurements, marsh‐type distribution maps, and literature‐derived marsh‐type‐specific carbon allocation parameters to estimate living biomass carbon stocks and vegetation‐derived burial rates across tidal marshes of the U.S. East and Gulf Coasts. Among tested vegetation indices (VIs), the Green Normalized Difference Vegetation Index (GNDVI) showed the strongest relationship with field‐measured above‐ground biomass (AGB) across seasons and marsh types. Applying the calibrated GNDVI–AGB relationship, we mapped annual peak AGB and used seasonal AGB differences as a satellite proxy for net above‐ground primary production (NAPP). By combining remotely sensed AGB with marsh‐type‐specific allocation strategies, vegetation carbon fractions, and below‐ground burial efficiency, we quantified regional living biomass carbon stocks and vegetation‐derived carbon burial rates. Our results suggest, along the East and Gulf Coasts, mean living biomass carbon of about 832 ± 202 g C m ⁻² , corresponding to a total of 11.1 Tg C, and a mean vegetation‐derived carbon burial rate of 70 ± 47 g C m ⁻²  yr ⁻¹ , totaling about 0.94 Tg C yr ⁻¹ . These vegetation‐derived burial rates are comparable to those of seagrass meadows and mangrove forests, demonstrating that coastal marshes function as similarly effective blue‐carbon sinks despite differences in plant structure and productivity. This study demonstrates that remote sensing provides a transparent, scalable, and cost‐effective approach for monitoring blue‐carbon dynamics and informing coastal management strategies.