Climate change is shaping our coastlines – and, as it turns out, the forests that live there. A new study published April 4 in the journal Ecological Applications found that a significant portion of the wooded wetlands in a coastal nature reserve in North Carolina’s coastal plain have been haunted for several decades. became – very large stands of dead, leafless trees.
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‘Ghost forests’ spread across US coastal regions
“The wooded wetlands of North Carolina are extremely vulnerable to climate change,” said lead author Emily Ury, a recent doctoral student in biology at Duke University. Ury and her co-authors determined using satellite images from the U.S. Geological Survey that up to 11 percent of the area once covered by forest had deteriorated to ‘ghost forest’ between 1985 and 2019, causing a shift in bare cypress. and hardwood swamps to woody shrubs or salt. During the period, about 30 percent of the wildlife sanctuary switched to another vegetation, and nearly 3,000 acres of land disappeared completely into the ocean.
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Ecologists say there may be more changes in the area.
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“It’s going to be part of a major ecological transition along our coastline as we penetrate our climate future,” said senior author Emily Bernhardt, an ecologist at Duke University.
Most trees do not like salt water. “A tree is constantly trying to absorb nutrients through its roots,” says Bernhardt. “And if there’s too much salt, they end up taking a lot of salt instead of nutrients.” Furthermore, seawater adds sulfate to the soil, which can become toxic to the trees.
The swamps that these wetlands occupy forests are incredibly important ecosystems. But the potential loss of the forests is still a major concern, Bernhardt says. Their disappearance will also mean the loss of many of the creatures who trust in it.
Trees and the soil beneath them also contain a lot of carbon, says Ury. “Keeping the soil in place will be very important in the future to prevent the release of carbon into the atmosphere, which will only cause climate change.”
A number of overlapping factors have contributed to these changes, including the steady rise in sea level, historic agricultural stressors such as ditches and canals, and extreme weather, all of which merge to push salt water inland. In particular, the ghost forests appear to have been encouraged by a series of extreme weather conditions, including a number of years of drought (preventing fresh water from washing up accumulated salt), fires and in August 2011 by Hurricane Irene.
“One of the great things about this study is that it showed that the gradual transition from forest to swamp that you would expect with sea level rise was really through Hurricane Irene,” said Matt Kirwan, an associate professor at the Virginia Institute of Marine Science. who were not involved in the research.
The authors saw this ghost forest along the roads and canals, Ury says, and they suspected it was due to saltwater intrusion. But from space “you really see the extent of these sites dying, and it goes beyond what we originally thought.” And although maps with the projected sea level rise often focus on the outside of the coast, Bernhardt says, salt water can seep further inland than you might think. Some of this forest loss and flora change, for example, occurred near canals more than half a mile from the water’s edge.
[Related: Forest fires leave behind charcoal—and it might be toxic for years]
The area the researchers studied is protected, making the deaths of the tree all the worse. “We have worked very hard through legislation and protection to capture these remaining wooded wetlands, and now they are threatened by something that does not respect these boundaries,” Bernhardt said.
And these results are not necessarily unique to North Carolina, Kirwan says. This pattern is observed throughout the American Atlantic coast, especially in the Mid-Atlantic and Southeast.
“The findings they have historically observed are only going to sharpen,” he said. “In the future, swamps will replace the coastal forests at a faster rate.” The swamps themselves are, of course, not infinitely resilient.
“If there is no room for the swamps to migrate, if there are cities or infrastructure in the way, then the continuous loss of the existing swamp may exceed the ability of swamps to migrate inland.”
Ury wants to see ecologists focus more on potential strategies to mitigate problems such as the loss of wetlands.
‘As ecologists and environmental scientists, we spend a lot of time quantifying the bad. And I think it’s high time we started exercising our ability and creativity towards solutions. ”
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