The meeting of the North and South Rivers (at left) and their shared inlet to the Atlantic Ocean, which formed in 1898. Credit: Bill Richardson
Key points:
- Sediment, not water, is a key factor to keeping salt marshes flourishing in a storm.
- Scientists say that, while sediment is treated like trash, it’s actually a viable treasure.
- Researchers urge a re-infusion of sediment be done if dredging a marsh is found necessary.
A new study published in the Journal of Geophysical Research shares some positive climate change news—salt marshes, critical habitats threatened by rapid sea-level rise may have the ability to thrive despite higher water levels. The key factor that determines whether salt marshes collapse or flourish involves not water, but sediment.
For the study, researchers looked back to 1898 when a vicious Nor’easter battered the Massachusetts coast with hurricane-force winds, rain, and a 10-foot storm surge. Before 1898, the North River took a hard southeastern turn, flowing behind a barrier beach for about 3.5 miles before it emptied into the Atlantic Ocean. A forceful hit by Portland Gale shortened that journey by 3.5 miles.
“It was a terrible storm,” said author Brian Yellen, research professor of earth, geographic, and climate sciences at the University of Massachusetts Amherst. “But it provided us with the rarest of things—a real-world, long-term experiment showing us how salt marshes, like those along the North River Estuary, may respond to rapid sea level rise in the coming years.”
Rising ocean levels pose a real threat to the loss of salt marshes, which are essential habitats for migrating birds and juvenile fish. Marshes also provide critical ecosystem services, including protecting coastlines from storm damages. Sediment has historically been viewed as a problem because it clogs up shipping lanes, so dredging the deep channels and dumping the sediment to sea has become standard practice.
Yellen points out that while we treat sediment as if it’s trash, it’s a viable treasure. He says he’s not advocating to end dredging, but instead have in place a compensatory re-infusion of sediment into the affected estuary system when dredging is deemed necessary.