What Happened to Our Salt Marshes

Since colonial times, a significant portion of our nation’s salt marshes have been destroyed, degraded or altered by agriculture, mosquito-control channeling, urban development, and other legacies of human activities. On Cape Cod, 38% or about 7,000 acres of our historical salt marshes have been lost or severely degraded.

Roads and other structures, especially those with culverts and tide gates, bisect and damage marshes by restricting the tidal flow that nourishes them. When tidal flow is restricted, these once-saline environments change to a brackish or freshwater condition in which native salt marsh vegetation suffers. Typically, these marshes become colonized by common reed (Phragmites australis), which forms dense stands 12 feet tall or higher. As invasive or freshwater species take over, a major shift in wildlife use occurs, and formerly diverse communities of marsh inhabitants are replaced by fewer species.