Mid-Atlantic
U.S. Forest Service’s Forest Health Protection “Ghost Forests Map Viewer.” Featured regions are in North Carolina. Each pixel represents 14 to 911 acres of land, and hundreds to thousands of dead trees. Screenshot © Dr. Chris Asaro / USDA FS

USA - Dead Tree Standing: Saltwater Threatens Coastal Forests and Ecosystem Services

Sea level rise is causing ghost forests to expand along the east coast, with hotspots in New Jersey, Maryland, and North Carolina. Salt marshes are migrating to take the place of wetland forests, causing a transition of ecosystem services. Water quality and quantity will decrease as a result.Hundreds of thousands more acres of forests are set to transition to ghost forests by 2100.

Dr. Chris Asaro has spent the last eight years tracking forest health for the United States Department of Agriculture’s Forest Service. His speciality for the last year has been mapping the large expanses of dead trees that are spreading along the East Coast of the United States. Hundreds of thousands of acres of gray and gnarled pine, cypress, and maples, many of them rotting on the ground, are the result of saltwater that has spread underground from the Atlantic Ocean, slowly killing trees by poisoning soil.

Asaro and other authorities call these dead stands of trees “ghost forests.” They have developed in at least eight states along the seashore, from New Jersey to Florida. More than the emotional distress, the increasing number and expanse of dead trees illustrates the consequences of climate change and sea level rise on ecosystems vital to coastal communities. Asaro, who manages the Forest Service’s Southeast Forest Health Monitoring Program, is generating digital maps to track the spread of ghost forests on the southeastern coast.

“It’s the rapid change that is the most concerning,” said Asaro. “We just don’t know what all the effects are going to be.”

As sea levels rise at rates up to 5 millimeters per year on the East Coast, saltwater is continuously pushing inland as far as 15 feet per year, aided by strong storm events that deposit salt on top of the soil. The result is mass tree death all along the coast, with hotspots in New Jersey, Maryland, and North Carolina.

Growing forests serve multiple benefits. They protect coastlines from erosion, buffer storm surges, provide wildlife habitats, and assure water quality and quantity. Mass death of trees injures those assets, and also damages local economies. As it intensifies, saltwater intrusion will shrink the supply of coastal wood for the timber industry, and the rural economies that depend on it.

Some of the tree species at risk from saltwater intrusion are not just ecologically beneficial, but historically significant. The Atlantic White Cedar, a New Jersey native species with blueish green leaves sacred to the Lenape tribe, was cut down in magnitudes with European settlement. Only 25,000 of the original 125,000 acres remain, and they are New Jersey’s primary victim of ghost forest conversion.

Saltwater intrusion presents a unique threat to wetland forest ecosystems, which are historically known for their resilience. “Normally, you can pretty much do whatever you want to a forest and it grows back. Wildfires, insect outbreaks, hurricanes, clear cutting, those are all things that the forest recovers from,” said Dr. Kirwan, an associate professor at the Virginia Institute of Marine Science. “Ghost forests aren’t like that. Once the saltwater intrudes, that forest is gone forever.”

Though the Forest Service started their mapping efforts last year, the results are already striking for North Carolina. More than 56,600 acres of forests have been converted to ghost forests – and that’s only part of one state.

In Maryland, one study found 84,000 acres of ghost forest conversion. Another study predicts a similar fate for 230,000 acres of Chesapeake Bay forests by 2100.

To Duke University Professor Dr. Emily Bernhardt, the ghost forests look “like graveyards.”

Trees are sensitive plants adapted to just the right conditions of sunlight, pH, and salinity. They also require a lot of freshwater. As wetland soils become saltier, trees draw out the water from the soils and leave behind the salt in the root zone, where new seedlings germinate. Coastal forest seedlings are adapted to freshwater conditions, where salinity is under 1 part per thousand. Today’s coastal wetland soils are measuring around 5 parts per thousand, with some areas as high as 15.

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