As rising sea levels push salt water into low-lying coastal areas, beaches aren’t all that’s affected. Deciduous trees that rely on fresh water to live slowly get poisoned by the invading sea. This leaves what’s known as a ghost forest, decaying trees standing in or near brackish water. Researchers at Duke University recently studied the North Carolina coast to see how much of it is covered by ghost forests, and they found the problem has increased substantially over the past few decades.
The team examined satellite images of 245,000 acres in the state’s Albemarle-Pamlico Peninsula taken between 1985 and 2019. They found that during that stretch, 11% of the trees within that acreage had been turned into ghost forests. Their findings were published in April 2021 in the journal Ecological Applications.
Emily Ury, a researcher at Duke, says sea level rise and land development are “really squeezing out what is the last of this native habitat and creating a really big problem for the animals that live there because they have nowhere else to go.”
This particular stretch of land – the Alligator River National Wildlife Refuge – is a unique protected area with endangered animals, including red wolves and red-cockaded woodpeckers. The refuge was established in 1984 to protect these animals and its forested wetlands, most of which are within two feet of sea level.
Compounding the issue of the encroaching sea are ditches and canals throughout the region that were built to drain water. Now, they’re helping the briny water move further inland and change the makeup of soil. The salt sucks moisture from plant cells and seeds, making it difficult for new tree seedlings to sprout. Trees that are more sensitive to salt can’t reproduce and begin to die off.
This isn’t just an issue for the plants affected.
Ury explains, “In addition to being a really excellent habitat to wildlife, these wetlands also store a tremendous amount of carbon in the living biomass, in the plants and in their soils below ground. So, losing these forests, particularly as they transition to salt marsh or what would be worse if they were to be lost to open water, it releases all of that carbon in that vegetation and in the soil back into the atmosphere. And that’s what we are really concerned about, because this carbon dioxide being returned into the atmosphere contributes to climate change and basically just feeds back into this cycle.”
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Nearly 47,000 acres of forest have been lost in the study area since 1985, with 21,000 acres of ghost forest formation. Much of this came in 2012 following Hurricane Irene. The storm hit in 2011 after five years of drought. A six-foot storm surge cascaded through the refuge more than 1.2 miles inland. Researchers say the damage was so extensive, strands of dying and downed trees could be seen in space just a few months later.
Between all these issues, the study area has lost about a quarter of its tree cover since 1985. Researchers hope what they take away from their study of the North Carolina coast may help other areas that are starting to see similar impacts of sea water intrusion.
Ury says, “Because of its geological location, North Carolina is just ahead of other coastal areas in terms of how far sea level rise has progressed. Lessons learned here could help manage similar transitions in other places.”
She also said they could help determine which areas are likely to be vulnerable in the future.
How can coastal communities address these changes? Ury says they need to adapt to something that will thrive and provide habitat benefits, even if it’s different than what was there before. She says that’s better than losing the land to open water. She hopes that the steps they take in North Carolina can provide some ideas to places that haven’t yet been hit as hard.
The NOAA says other areas currently experiencing expanding ghost forests include the Chesapeake Bay watershed and the Mississippi Delta region of Louisiana.Whizzco