Within a few years, skeleton-like stands of the giant evergreen tree will mar the landscape and ecosystem as the infestation of the hemlock woolly adelgid, an invasive insect, takes its toll.
For the past three years, the forest service and park service have been fighting the adelgids with a predator beetle designed to devour the hemlock marauder. But the beetle breeding laboratories can’t keep up, and it’s time to start preparing for the loss of this anchor tree species, according to Jim Vose, project leader at the U.S. Forest Service’s Coweta Laboratory in Macon County.
“Our lab is leading the research on what losing the hemlock is going to do to the Southern Appalachian ecosystem,” Vose said. “When it dies, there are going to be some big changes. One of the other things we are doing is trying to figure out what to do next.”
Vose has just received $300,000 from the federal government, a sum secured by U.S. Rep. Charles Taylor, R-Brevard.
“Western North Carolina has been hit particularly hard by this pest,” Taylor said in a press release. “Every single county here in the mountains is dealing with serious outbreaks. It is crucial that we find a way to eradicate these pests, and these funds should go a long way in accomplishing that.”
However, scientists have realized that eradicating the hemlock adelgid at this stage of the game is likely a pipe dream. While some of the money will go toward fighting the beetle, scientists are ready to launch research that will prepare the region to cope with the loss of hemlocks.
The loss of hemlocks will have a huge trickle down effect in the environment. It will alter soil nutrients, water quality and wildlife habitat.
“One of the unique roles of hemlock is it is the primary species that occurs along streams, and it has an important role in shading the stream,” Vose said.
Without the hemlocks’ shade, the water could be warmer, making it harder for trout to survive. The soil along the stream banks will be hotter and drier, forcing out moisture-loving salamanders. And when the hemlock topples over, the roots that once held soil in place will be lost, meaning more sediment is likely to runoff into the water. These examples are just scratching the surface of what dead hemlocks will mean.
“One of the other things we are doing is trying to figure out what to do next,” Vose said. “If you do have these large areas of dead hemlocks, what do you do to offset the negative impacts of the hemlock loss? Do you go in and remove it and harvest it and try to plant something back? It’s just daunting.”
Vose’s team isn’t giving up on the fight, however. A portion of the funding will be used to study the pros and cons of methods being used against the adelgid. There are only two real options for fighting the adelgid: the predator beetle and pesticides. Pesticides are being used regularly by the park and forest service to protect a few select hemlock stands until hopefully the predator beetles multiply enough to keep the adelgids at bay.
Vose will try to answer whether the pesticide drifts onto surrounding plants or makes it into streams, killing bugs other than the adelgid.
“What are the possible ramifications of losing those other insects in the soil or in the stream? Is the goal of trying to protect the hemlocks worth the other possible environmental risks?” Vose asked.
There is one potential tool in the fight that is yet unexplored: genetic resistance.
“There is not a high probability there is a genetic resistance, but there is a possibility,” Vose said, citing pockets of hemlocks that survived the adelgid as it worked its way down the Appalachian range from Maine to Virginia, wiping out hemlocks in its slow march south to WNC.
“Some of it might be they survived just because of luck, but there is a possibility there is some kind of inherent resistance,” Vose said.
Adelgids can kill a hemlock within five to seven years of infestation, according to observations in areas already struck. Vose said the warmer conditions of the South have allowed the adelgid to spread faster here than up north and could prove lethal sooner rather than later.
“We are probably within just a few years of beginning to see dead hemlocks,” Vose said.