Human structures hinder wetland rebuilding that protects against sea level rise

Researchers at The College of William & Mary say that human structures like dams and seawalls are disrupting natural mechanisms that allow coastal marshes to survive rising seas, according to a release. These wetlands, they say, could better resist sea-level rise if left undisturbed.

Coastal marshes are usually built up when excess sediment is deposited during periods of high water. Researchers say these areas aren’t being replenished as needed to protect against rising seas. Under normal conditions, the wetlands would adjust to higher waters by building vertically or moving inland to higher elevations.

Inhibiting structures include dikes and reservoirs that reduce water flow and the replenishing sediment it brings to marshes. Groundwater withdrawal and drainage systems can also cause marshes to sink, making them and nearby areas more prone to flooding.