Seagrass restoration plots hold through a second winter

Seagrass restoration plots established in the Aldwych estuary in 2024 have survived a second winter, with shoot density in the two larger plots now comparable to adjacent natural meadow.

Sofia Marchetti, who joined the marine conservation faculty this year and took over the project, is measured about what that means.

"Survival at three years is the standard by which most restoration is declared successful, and it is not a good standard," she said. "The plants being alive tells you the planting worked. It does not tell you the habitat works."

The project is instead measuring function: which species use the restored meadow, how much carbon the sediment is accumulating, and how the plots attenuate wave energy compared with natural meadow of similar extent. Early results on invertebrate colonization are close to reference conditions. Carbon accumulation is lagging, which is expected and which the project intends to keep measuring for considerably longer than three years.

One plot has failed. It was established in a location where the sediment supply had been interrupted, and Marchetti considers the failure the most useful part of the experiment. "Planting into a system that cannot hold sediment gives you a meadow that looks right and does not persist. We now have that documented on our own site rather than citing someone else's."

The reference data come from the long-running transect record at Prentice, which lets the project define its targets against an actual local history rather than a general expectation.