Drowning Marshes

Here’s an old saying about nature: Drown a salt marsh, drown a coastline. Okay, we made that one up. But it’s true. And you might hear it more in the future because marshes are threatened by rising sea levels.

But a team of researchers has developed a way to know that a marsh is in trouble before it vanishes—providing time to preserve and restore threatened systems.

Coastal salt marshes offer many benefits. They store carbon, filter the water, and provide habitat for wildlife and fishing grounds for people. And they act as a barrier against storm surges and rising sea level. As sea level rises, they build more extensive root networks that trap more sediments, elevating the entire bed.

But when the water level climbs too fast, or stays high for too long, it can drown the roots. So while the vegetation looks healthy, its days are numbered.

The researchers developed a computer model that assesses the health of the roots. The model used observations by a satellite and other details. They applied the model to the marshes along the coast of Georgia. And they compared their findings to surveys made on the ground.

They found that the root systems had been declining by about one percent per year over most of the study area—even though the amount of the plants above ground had been going up. It takes a while for what’s happening in the roots to show up above ground. So the study provides an early warning—and time to save the marsh, save the coastline.