As ‘Ghost Forests’ Multiply In Chesapeake Bay Region, Answers Lag Behind

ANNAPOLIS, Md. – If the District of Columbia were nine times larger, it still wouldn’t equal the area of forests lost to saltwater intrusion along Maryland’s coasts in the past decade alone.

Every July, when Heather Disque surveys the landscape from her state-issued Cessna, she documents thousands more acres of trees in death throes. It’s only a matter of a few years before they wither into desiccated husks and topple over, she said. By then, the ground itself likely will be wetter, having converted to a saltmarsh.

During her first few years conducting the aerial surveys, Disque was surprised by how rapidly the forests were failing. Then, she looked at computer climate models, showing which areas are expected to become inundated first because of sea level rise.

“A lot of these forested areas we’re seeing are in those predicted impact areas,” said Disque, who studies forest health as part of the state Department of Natural Resources’ pest management efforts. “So, it’s not surprising to see what was predicted is coming true.”

Across many of the low-lying shorelines along the Chesapeake Bay, formerly healthy forests are transforming into “ghost forests” — stands of dead trees sandwiched between marshes on lower ground and living forests on higher ground. Human-caused climate change is accelerating sea level rise, the main culprit behind the phenomenon, scientists say.

A similar process is playing out on coastal cropland, and a recent spate of research has begun to propose strategies to help farmers cope with saltwater intrusion. But no such aid appears to be in the offing for timber, the fifth largest industry in Maryland and the second largest in Virginia.

“The question I get over the last five years is what can a forest landowner do,” said Matthew Hurd, who oversees the Maryland Forest Service’s Eastern Shore region, which has been the epicenter of the ghost forest blight in the state. “And the answer is pretty abstract at the moment.”

He added, “If they’re already being impacted, it’s already too late.”

Matt Kirwan, a coastal ecologist with the Virginia Institute of Marine Science, is one of the region’s leading ghost forest researchers and owns a salt-impacted forest tract with his father in Maryland’s Dorchester County. It’s rare to find any formal advice for landowners, he said.

“The advice is basically ‘pay attention,’” Kirwan noted. “There are almost no recommendations.”

For many observers, ghost forests stand out as a palpable symbol of climate change.

“Some of the changes are really dramatic,” said Greg Noe, a U.S. Geological Survey wetland ecologist based in Delaware. “Ghost forests are enigmatic. They’re big changes. They’re an effective canary in the coal mine for demonstrating sea level rise on the landscape.”

They haunt coastlines along parts of the East Coast, bending around the Gulf of Mexico as well. The Chesapeake region has been particularly susceptible, experts say, because much of its land is sinking due to groundwater withdrawals and the falling of the Earth’s crust in the post-glacial period. As a result, the “relative” rate of sea level rise has been about twice the global rate.

Yet, paradoxically, the region’s shore-hugging trees are dying back at a significantly slower pace. Kirwan and a fellow VIMS researcher analyzed four decades of satellite imagery along the coastline from New Jersey to Virginia, finding that healthy forests retreated upland at a rate of 2.7 vertical millimeters per year. The relative sea level rose 5.5 millimeters per year over the same span.

Their scientific paper, published in 2023 in the journal Global Change Biology, estimated that forest retreat lags behind sea level rise by “roughly half of a century.” That finding has potentially big implications for how climate experts forecast landscape changes, Kirwan said. Existing computer models assume that forests disappear instantaneously when the water moves in instead of lingering for many years, as Kirwan found.

“Because it takes decades for trees to die, we’re never seeing the full extent of forest loss,” Kirwan said. “We won’t see the full extent of sea level rise until decades after it’s happened.”

Flooding induced by sea level rise is harmful enough just because of standing water. But the Atlantic’s seawater and the Chesapeake’s brackish water both contain salt, and that ingredient supercharges the ghost forest process, Kirwan explained. 

“Salt makes it much worse,” he said. “Some tree species can grow in standing water, but none can tolerate much salt. Forest retreat rates across the Bay are positively correlated with salinity of adjacent rivers.”

Ghost forests lurk several miles upstream along some rivers in Maryland and Virginia. In fact, Kirwan’s research found forest loss up to 6 miles inland from any major water body, a consequence of drainage ditches carrying salt-laced waters into the interior during strong storms and unusually high tides.

Disque’s aerial survey only focuses on the Delmarva Peninsula in Maryland from Talbot County south to Somerset County. Her most recent flight in July 2024 showed that 27,000 new acres of ghost forest had been created over the previous year, more than half of it classified as “severe” or “very severe” in nature. Since 2016, her mapping has uncovered about 415,000 acres of salt-affected forests on the peninsula, she said.

Maryland forester Hurd said that private landowners facing ghost forest encroachment should have the state perform a health assessment on their property. Weaker trees may need to be thinned to reduce stress on stronger specimens. Landowners may also consider harvesting trees before they lose their value as lumber, he added. But that’s only possible if the land around them hasn’t gotten too mushy to support heavy equipment.

Kirwan and his colleagues are trying to develop a fuller picture of the mechanisms behind saltwater intrusion in forests by studying 36 test plots on the oceanside of Virginia’s Eastern Shore. Standing in a ghost forest on a recent morning, Tyler Messerschmidt, a VIMS lab and field manager, suggested that there is another way of looking at the changes in the landscape.

“A lot of people are worried because the trees are dying here,” he said. “We’re trying to facilitate to the best of our ability successful marsh migration into these areas so that as marshes are eroding and drowning on one end, we have space for the marsh to form on the upland side.”

Some conservation groups say the best solution to ghost forests is to allow nature to take its course. They’re encouraging landowners to protect their increasingly wet properties from development by selling them as land trusts or easements.