After decades of devastation, a comeback for western NC forests
Posted April 20, 2020 10:02 a.m. EDT
Updated April 20, 2020 2:15 p.m. EDT
Great Smoky Mountains National Park — On the Spruce-Fir Nature Trail in the Great Smoky Mountains National Park, a forest that looks like it belongs in a fairytale grows on the slopes of Clingmans Dome. Soft green moss covers logs and rocks and tree trunks, muffling the sound of cars passing nearby. The trees grow so closely together in some places that they’re impossible to walk between.
In the mornings when the humidity is high, shafts of sunlight cut through the trees and pool on the rocky forest floor. Along the ridgeline, higher up near the peak of the mountain, the view opens and you can look down on the distinctive dark-green color of the spruce-fir forest.
But hundreds of dead trees spot the high slopes. They look like toothpicks, sharp and thin, and when the clouds come down across the mountain, there is something spooky about them.
These trees are the skeletons of Fraser firs, a species native only to the Southern Appalachians and a relic from the last Ice Age.
As conifer forests disappeared from the South when the glaciers retreated and the climate warmed, some trees found refuge on cool, high peaks. Fraser fir and red spruce, the two dominant tree species on these high mountains, form the base of a complex ecosystem full of plants and animals found nowhere else on earth.
But in the fall of 1957, something strange started happening. The Fraser firs on Mount Mitchell began dying at an alarming rate. It was the balsam woolly adelgid — a small, fluffy white insect from Europe that had been killing trees across Canada and the northeast. By the 1980s, it had spread across the Southern Appalachians — 67% of adult Fraser firs succumbed to the adelgid. Many that died remained standing, riddling the forest with stark, ghostly trunks.
But decades later, the Fraser fir is making a comeback.
“There was that first wave — it went through, wiped out the majority of the mature trees. Fortunately, there was regeneration,” Kevin Potter, a researcher at North Carolina State University, says.
Potter studies conservation genetics and forest health, and has kept a close eye on the balsam woolly adelgid and other invasive species that are devastating forests across the eastern United States. When the adelgid first made an appearance, there was some concern that spruce-fir forests would never be the same.
That fear wasn’t unjustified. Species that don’t have the natural defenses to ward off attacks from foreign invaders can be decimated. The American chestnut, which in the early 1900s made up more than 25% of eastern forests in some places, is all but extinct because of a fungus accidentally imported from Asia. No corner of the earth is untouched — even Antarctica is having problems.
A saving grace for Fraser firs, at least, is that the adelgid doesn’t kill young ones.
“There was a new cohort of trees, younger trees, to grow up underneath the dead trees,” Potter says. “Those should probably, by now, have been infected if we were going to expect another wave of intense mortality like we saw back in the ’60s through the ’80s. And that hasn’t happened.”
Now, people who monitor forests in the Great Smoky Mountains National Park and the surrounding areas barely see any of the once insatiable pests.
“In the earlier years of the infestation, the trees would just look whitewashed with adelgid,” Kristine Johnson, supervisory forester at the Great Smoky Mountains National Park, says. “When we have new interns, we need to show them what they look like. Sometimes we can’t find any.”
Johnson has been working with invasive species like the balsam woolly adelgid for over four decades. In the 1980s, the situation looked apocalyptic — some researchers wondered if there would be anything left, and whether the Fraser fir would go the way of the American chestnut.
But in the late 1990s, Johnson and other park rangers started seeing a decline in the adelgid population after about 10 years of managing for them. That pattern of decline, she says, was what they were hoping for.
Often when exotic insects first arrive on the scene, there’s a severe outbreak — and then the forest starts to fight back. The attacked species may begin to develop genetic resistance. Predators and parasites take advantage of the new creature in their midst. And if the ecosystem fights hard enough, the invasive species becomes more or less naturalized.
“And that is in fact what we’re seeing with the Fraser fir,” she says.
That’s good news not only for this rare ecosystem, but also for North Carolina’s extensive Christmas tree industry. Fifty million Fraser firs are grown on Christmas tree farms in the state.
But like natural stands, trees grown on farms are also susceptible to the adelgid, Jill Sidebottom, a mountain conifer specialist with NCSU, says. She works closely with Christmas tree farmers on pest management.
“I’ve been doing this since 1988,” Sidebottom says. “When I first started working, balsam woolly adelgid was the worst pest that Christmas tree growers had. They had a very difficult time controlling it. But within the last 10 years I guess, it’s become less and less of a problem for them.”
Christmas tree growers have an advantage that forest managers do not — their Fraser firs aren’t spread out across steep and inaccessible ridges. While forest managers can only treat trees near roads, farmers can watch over all of their trees for signs of pests. But some researchers, including some at NCSU, are working to create a longer-lasting deterrent than insecticides — trees that are genetically resistant to the adelgid.
“Even though we are getting pretty good control of this pest, it would still be nice to have trees that were resistant,” Sidebottom says. “And then of course their hopes are to be able to reintroduce those more resistant individuals into natural stands.”
A long-term study in the Great Smoky Mountains National Park shows that the number of adult Fraser firs has increased over the last 30 years. On Clingmans Dome, the number of firs is estimated to have nearly tripled. However, spruce-fir forests are facing a whole host of other problems — namely climate change, which can exacerbate problems with invasive species.
“The end story for Fraser fir will be climate change. If we were to have a period of warm winters and hot, dry summers, the trees will be stressed,” Johnson says. “I wouldn’t be surprised to see a resurgence of balsam woolly adelgid under those conditions, where the trees are really stressed and less able to withstand an adelgid attack.”
One way that people can help prevent the spread of invasive insects is to not transport firewood away from where it was cut. Firewood can be like a Trojan horse — a tried-and-true way for bark-dwelling insects to sidle into a new and unsuspecting habitat.
Thorough inspections and quarantines on goods flowing into the country, too, may help slow the introduction of new invasives, Johnson says.
“You ask me what keeps me up at night?” she asks. “The fact that this didn’t really have to happen.”
But overall, Johnson says that the story of the Fraser fir is a hopeful one. The destruction of this rare ecosystem, which seemed like a real possibility in the ’80s as the trees died in droves, ended up being not so probable after all. And in places that were once covered in dead trees, Johnson is now seeing regrowth.
“It’s pretty encouraging,” she says. “But then you think, well, 50 years from now, with the climate changing and the air quality declining, maybe not so much. Our ability to see into the future only extends so far — but it made me a little more open minded.”
Anne McDarris is a master's student from Cary majoring in journalism. She has experience working for the National Park Service and UNC’s Research Communications Office. She looks forward to a career in science and environmental reporting.