Forty years ago, people in the United States imported some trees from Asia. Unknown to anyone, the hemlock woolly adelgid was along for the ride.
The undetected pest came with an appetite for hemlock trees, and there are no natural enemies here to stop it.
In their natural environment, insects are a key part of the ecosystem Even if a leaf is munched by a caterpillar, the insect is snapped up by a bird. All is in balance.
But in the Smokies, the hemlock woolly adelgid threatens that balance because it left its enemies back home in Asia.
Laura White, nature center supervisor at Hemlock Bluffs Nature Preserve in Cary, explains how a towering hemlock can be brought down by the depredations of the woolly adelgid.
"It's a little fuzzy little critter and they suck the trees dry of the fluid." White says that wherever the insect sets up housekeeping, everything beyond it on the branch just turns brown and dies off.
The hemlock woolly adelgid is a pest specific to hemlock trees, which are prevalent in the Southern Appalachian Mountains but rare in the Piedmont.
And the Hemlock Bluffs Reserve is the only virgin stand of hemlocks known.
White says, if unchecked, the hungry pest could do immeasurable damage.
"A vast majority of the Southern Appalachians are covered in hemlock trees so it would really reshape the mountains and the ecosystems of the mountains," she said.
Researchers in Connecticut are field testing a small beetle from Japan, a natural enemy to the adelgid. If a solution isn't found, White says it's possible the adelgid may soon threaten even this rare hemlock cove.
But it's thought that the population of hemlock trees along Swift Creek is small enough that natural pesticides could ward off the hemlock woolly adelgid. Unfortunately, employing that approach in the mountains would be like using a squirt gun on a forest fire.