• Drowning, as sea levels rise and land sinks — Soil in the marsh is constantly compressing, in a process called subsidence.
“You get a sense of water level rising, but it’s really not. The land is sinking. We have that all over our coast,” Dr. Robert Twilley said.
Combined with sea level rise, wetlands can be over-saturated.
“The wetlands have to build soil at a rate that it’s sinking in order for the water level to stay the same or, literally, the wetlands drown,” Twilley said.
• Erosion, as wind and wave action work on barrier islands — According to Twilley, the term “erosion” is overused. It applies mostly to the wear and tear the islands along coastal bays experience. Those islands brace the impact on wetlands.
• Dieback, as grasses are overwhelmed with saltwater — As erosion occurs, saltwater has moved farther inland, called saltwater intrusion.
Twilley said dieback occurs when, “you put a big pulse of salt in there and it basically kills the plants.”
An impulse of salt causes the marsh grasses’ roots to weaken and shrink, loosening their hold on the soil, causing the marsh to “melt away.”
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