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Growing ghost forests full of dead trees are harbingers of the threat of rising saltwater

DARE COUNTY, N.C. — Across acre after acre on the North Carolina’s coastal plains stand ghosts of what once was. Instead of green maritime forests, you’ll find marshes filled with bare trees.

The culprit behind these forests of dead trees, is saltwater intrusion. Dr. David Logamasino with the Coastal Studies Institute explains that’s when water from the ocean gets into places that aren’t used to that much salt and lasts long enough to physically change the environment.

“It is a natural process,” he said. “This is a transitional zone as we go from a more terrestrial environment to now a more aquatic environment.”

What isn’t natural however, is how fast it’s happening. Logamasino the state of North Carolina has seen 47,000 acres of forest turn into these ghost forests and across the U.S. that’s 3.3 million acres, the equivalent of two Delawares worth of forests disappearing.

“That forested environment that was here, was serving some ecosystem services,” he said. “It was able to uptake some carbon dioxide and store that in the biomass parts of the tree. It’s also serving as different habitats for animals, birds, mammals.”

Drought and storm surges speed up the process of saltwater intrusion but as the ocean rises its saltwater is going further inland as well. Sea level has already risen four inches in the past 30 years and NOAA expects it to rise another 10-12.

Spencer Rhea, a PhD student at Duke University, is working to figure out where that saltwater is headed. As part of a NC Sea Grant and Space Grant study, he’s using field and satellite data to map the development of ghost forests over the past 40 years.

“We’re going to build a model that can predict the saltwater concentration based on the color of the water,” he said. “Once we know where the salt is coming in and where it’s accumulating, we can kind of predict where a forest might die.”

While the dying trees are a very visible symbol of saltwater intrusion, Rhea said ghost forests far from the only concern.

“We like to call ghost forests the canary in the coal mine of climate change because it’s a really easy visible sign that sea level is rising,” he said.

As that sea water moves further inland it threatens coastal agriculture and infiltrate the ground water table, meaning reduced yields and limiting what can grow where.

Saltwater intrusion can also have a serious impact on the drinking water supply for those who live along the coast, either by breaching wells or flowing upstream.

“It’s really hard to push that saltwater out,” Logamasino said. “You need a lot of freshwater to sort of clean out that ground water system.”

In recent years, that’s been a growing problem for Louisiana and communities on the Gulf Coast. With the Mississippi River near record lows due to extreme drought, saltwater has been flowing further upstream into the river and threatening the drinking water for hundreds of thousands.

Once his study is complete, Rhea will collaborate with researchers out of Louisiana. Their hope is that this research can not only help predict the formation of ghost forests but can help guide infrastructure solutions that can protect areas from rising saltwater.

“That’s going to have consequences for what the landscape is going to look like in the future,” he said.

(WATCH BELOW: Bridge designed to avoid flooded road to Outer Banks opens on NC coast)

Michelle Alfini

Michelle Alfini, wsoctv.com

Michelle is a climate reporter for Channel 9.