A test to see if old Christmas trees can help shore up eroded sand dunes has shown some success at Popham Beach State Park.
In some places, rows of trees have been completely covered in sand, creating ridges that are now colonized by dune grass.
That's a promising development after the dunes were wiped out in back-to-back storms this winter. Beach erosion is a natural process and typically sand depleted in the winter gets restored in warmer months.
But when storm damage puts human infrastructure at risk, dunes are a critical shield, said Peter Slovinsky of the Maine Geological Survey in a tour of the restoration area.
"Humans love coastlines, and we've put a lot of infrastructure in harm's way, so sand dunes are nature's way of protecting the uplands," Slovinsky said.
Early this year, the Maine Department of Agriculture, Conservation and Forestry asked for donations of old Christmas trees for the project. The response was overwhelming, bringing in about 1,500 trees, said Sean Vaillancourt, manager of the state park.
More than 500 trees were eventually used in the project, arranged in rows between the surf and the park's bath house and parking lot.
The idea is that as sand is carried over the trees by waves or blows up the beach, it will catch on the rows, eventually swallowing the trees and leaving an area where dune grass can set in. From there, the dunes can grow and provide a natural buffer from the ocean.
Maine adopted the technique from other states including North Carolina, according to Slovinsky. The aim is to see if these natural methods can be adopted by other communities trying to recover their damaged dune systems.
"So the idea was to, again, try to build that dune out from a natural perspective, using green infrastructure or living shorelines. They're kind of called nature based solutions. Is another word for it, to try to mimic the natural processes that occur," Slovinsky said.
"We can't just go in and build a sea wall here. That's not allowed in the dune system in Maine. So we have to try to capture nature's natural functionality in terms of kind of rebuilding these systems," he added.
Nature-based techniques could augment traditional dune restoration methods, such as mechanically dragging sand onto depleted dunes, replanting dune grass, or replenishing beaches from a nearby dredge or by bringing in sand, Slovinsky said.
So far in Popham, the tree restoration project has had mixed success. Slovinsky said he expected more sand trapped in the rows. A course change of the nearby Morse River likely shortened the beach and therefore the amount of sand blowing into the trap, he added.
The state expects to monitor the project for a couple years to gauge its success. It could then inform best practices for broader use.
