Researchers at Northeastern University have developed a system of interconnected circular mats of floating vegetation dubbed the “Emerald Tutu,” which they believe could help protect Boston Harbor from the perils of rising sea levels.
In a statement, Northeastern said the Emerald Tutu project, a play on Boston’s famed Emerald Necklace of parkways and waterways stretching from Boston to Brookline, currently has one mat in the water in Salem, with a second set slated for launch in Boston Harbor. A date for the harbor launch hasn’t been set.
The project is a collaboration with Stone Living Lab, which bills itself on its website as an initiative for testing and scaling up proposals to promote climate adaptation, coastal resilience, and ecological restoration in the Boston Harbor Islands National and State Park.
“We’re just waiting for the boat” to get started on the harbor, said Julia Hopkins, an assistant professor of civil and environmental engineering at Northeastern and lead scientist for the Emerald Tutu project, in the statement.
Northeastern said the circular mats that comprise the “tutu” are each about 7 feet in diameter and designed to have marsh grasses growing on top and seaweed below.
In addition, the tutu is meant to feature walkways to allow pedestrians to experience nature, the statement said.
Hopkins deployed an initial Emerald Tutu test mat off an East Boston pier during the spring of 2021, and she said in the statement that researchers were pleased when they pulled it out of the water last summer and discovered a significant amount of vegetation growing on it.
“We didn’t expect as much grass or seaweed to grow,” Hopkins said. “We didn’t realize it would colonize that easily and that much.”
The mats are composed of biodegradable material, such as coconut fiber, wood chip byproduct, burlap canvas, and marine-grade rope, and they won’t pollute the environment if they break loose and get lost at sea, according to the statement.
The university said the mats absorb wave energy and help mitigate the flooding that increasingly threatens to inundate Boston and other coastal cities. The more vegetation that grows on the mats when they’re in the water, the more wave energy they can absorb, thereby limiting flooding, the statement said.
“It functions as a marsh without being a marsh,” Hopkins said in the statement, adding that the “basic idea takes some of the theory we have about how nature is supposed to be protecting shore and applying that to something we can use in urban environments.”
Plans are in place for “a massive” Emerald Tutu pilot project next summer, with an exact location for the vegetation mats yet to be determined, the statement said.
“This is really about the vision communities have for what they want their future to look like,” said Laura Kuhl, an assistant professor in Northeastern’s School of Public Policy and Urban Affairs who’s also working on the project, in the statement.
Time is of the essence.
A federal government study released in February predicted that by 2050, sea levels along US coastlines will be about a foot higher than they were in 2000. That increase will be even sharper in Boston and elsewhere in the Northeast: The region is likely to see 16 inches of sea level rise compared with 2000 levels.
Boston already experiences some of the worst high-tide flooding in the nation.
In the later part of the century, things will get even more dire. By 2100, under a worst-case scenario where emissions keep increasing, researchers estimate that sea levels around Boston could rise by 6.4 feet. Even with major climate policies in place, the region could see sea levels pushed up by more than 2 feet by the end of the century.
Sea level rise is already causing more frequent coastal flooding in low-lying areas along Massachusetts’ shorelines and has put hundreds of thousands of homes at risk. Reports show these risks disproportionately affect already marginalized communities.
“It’s not going to be one solution,” Kuhl said of battling rising sea levels and storm intensification stemming from climate change, in the statement from Northeastern. “It’s going to be building up a portfolio. The Emerald Tutu is expanding the options.”