Soil erosion alters coastal wetland stability by changing the balance between sediment supply and marsh elevation maintenance. Wetlands survive where sediment inputs and organic matter accumulation keep surface elevation ahead of relative sea level rise. When upstream or shoreline erosion reduces the right kind of sediment, marsh surfaces lose the material they need to build elevation, increasing susceptibility to inundation and dieback. Conversely, excessive or highly turbid sediment can smother vegetation and reduce photosynthesis, so the effect of erosion is context dependent.
Causes and physical mechanisms
Erosion-driven changes originate from inland land use, river regulation, and coastal wave action. Damming and channelization trap sediments that formerly fed deltas and marshes, a dynamic described in work by Daniel R. Cahoon Louisiana State University who has documented how reduced sediment supply limits marsh accretion. Shoreline retreat driven by storms and sea level rise promotes edge erosion, detaching marsh soil and exporting organic material offshore. Classical field studies by John M. Teal Woods Hole Oceanographic Institution established how vegetation–sediment interactions determine marsh resilience, showing how physical removal of soil undermines plant root systems and the structural integrity of peat-rich soils.
Consequences for people, ecosystems, and climate
Loss of wetland stability produces cascading consequences. Reduced marsh area diminishes ecosystem services such as storm buffering, nursery habitat for fisheries, and carbon sequestration. US Geological Survey scientist David A. Sallenger United States Geological Survey has characterized how shoreline erosion and wetland retreat increase exposure of communities to coastal flooding. Cultural and territorial impacts are acute in regions where wetlands support traditional livelihoods and land identities; for example, many Gulf Coast communities face both economic and heritage losses as marshes convert to open water. From a climate perspective, destabilized marsh soils can shift from carbon sinks to carbon sources when peat oxidizes or is eroded away, altering greenhouse gas balances.
Restoration and management that address the root causes of erosion — reconnecting riverine sediment, reducing upland erosion through land stewardship, and designing living shorelines — can restore the material flows wetlands need. Effective responses require integrating ecological science with local knowledge and governance to preserve both the physical stability of wetlands and the human communities they protect.