The University of Georgia analyzed about 1,100 soil cores from Spartina alterniflora marshes and found nearly 75% of the studied area shows declines in below-ground biomass, with over 25% now in a vulnerable state. Scientists link root and rhizome losses to longer submersion caused by accelerating sea level rise, which reduces oxygen to roots and undermines marsh elevation gain. Authors recommend sediment addition, tidal restoration, and protecting inland migration corridors to boost resilience.
Georgia’s Salt Marshes Are Losing Their Underground Foundation — Study Warns Rising Collapse Risk
A long-term scientific assessment reveals that the subterranean support system of one of the largest salt marsh complexes in the United States is quietly deteriorating along Georgia’s coast — even where marshes still look healthy from above.
Study Findings
Researchers at the University of Georgia spent more than a decade collecting and analyzing roughly 1,100 soil cores from marshes dominated by the grass Spartina alterniflora, which shapes much of Georgia’s shoreline. Their results, published in the Proceedings of the National Academy of Sciences, show that nearly three-quarters of the studied area have experienced declines in below-ground biomass — the dense roots and rhizomes that bind soil and help marshes keep pace with rising seas. More than a quarter of the marshland has already moved into a vulnerable state where its capacity to resist erosion and maintain elevation is compromised.
Why It’s Happening
The research links much of the below-ground decline to marsh platforms being submerged for longer periods, which reduces oxygen availability to plant roots and weakens root systems. Sea level rise along the U.S. Southeast coast has accelerated in recent decades, and NOAA has documented faster-than-average increases in parts of Georgia. University of Georgia marine scientist Merryl Alber, a co-author of the study, warned that "there are reasons to believe it might be intensifying even more in the next few years."
Consequences
Salt marshes provide vital services to coastal communities: they buffer storm surge, sequester carbon, support fisheries, and stabilize shorelines. When below-ground biomass declines because of extended submersion, marshes lose their capacity to build elevation and trap sediment. That loss increases the risk of marsh collapse and large-scale die-offs, with serious implications for shoreline protection, habitat, and carbon storage.
What Scientists Recommend
The study’s authors recommend a suite of management actions to bolster marsh resilience: adding sediment to raise marsh elevation, restoring natural tidal flows to improve oxygenation and sediment exchange, and protecting inland corridors so marshes can migrate landward as seas rise. The research is already prompting scientists in other states to measure below-ground biomass rather than relying solely on surface appearance.
How People Can Help
Communities and individuals can support salt marsh protection by backing local coastal conservation organizations, advocating for policies that reduce greenhouse gas emissions and pollution, and volunteering with habitat restoration projects. Early intervention and targeted restoration can help preserve the shoreline protection and ecological services these marshes provide.
Bottom line: Declines in underground root networks threaten the stability of Georgia’s salt marshes. Without action, those losses could translate into increased coastal erosion, weaker storm defenses, and lost habitat.
