For as long as Ed Callahan can remember, the trees lining a scenic stretch of the Pennsylvania Turnpike that winds through the Laurel Highlands have stayed mysteriously twisted and bare.
"Since I was a kid, I can remember wondering what the heck was wrong with those trees," said Callahan, 40, now the director of forestry in Western Pennsylvania for the state Department of Conservation and Natural Resources.
Grass and wildflowers thrive in the area, but the trees die. Callahan blames road salt, although theories range from diesel fumes to gypsy moth infestations, and even a great fire.
"If you ever drive behind a truck in the winter, you see those big clouds of salty mist kicked up behind them," Callahan said. "When that salt gets on the branches, the trees get stunted, and a lot of times they die."
The mutant trees line almost 55 miles of turnpike east of Irwin, Westmoreland County. The worst are concentrated in a 20-mile long, 100-feet deep stretch straddling the border between Westmoreland and Somerset counties. Most are on state forest land.
Trees that are still living sprout short, spiky twigs, called witches' brooms, from their gnarled limbs. They become increasingly stressed and eventually die, Callahan said.
The trees this year are in the worst shape that Callahan and many people who live along the turnpike remember.
"There's more dead every year," said Rich Giles, 58, of Donegal, Westmoreland County, who has lived above the turnpike for 28 years. "There were some dead (trees) when I moved in, but this is the worst it's been."
Winters in the Laurel Highlands are harsh. The elevation keeps temperatures about 10 degrees colder than in Pittsburgh, and wind from the west whips the often ice- and snow-covered ridge.
As a result, the stretch of turnpike between Donegal and Somerset -- serving 32,000 motorists a day, 35 percent of them truckers -- is the most heavily salted in the state. Workers sometimes spread 800 pounds of salt per mile during a storm, said John Stewart, the turnpike's director of maintenance.
"We have a joke that there are two seasons in the Donegal-Somerset area -- the Fourth of July and winter," Stewart said.
Fifty-one accidents occurred on that stretch of road in December, and the monthly average was 26 last year, according to state police. Stewart is certain the turnpike commission's "bare-road policy" helps save lives, but he isn't convinced the salt is killing trees.
"It befuddles me to hear that this is the major source," said Stewart, who, like others, wonders if gypsy moths, drought or diesel exhaust are the culprits.
Officials haven't conducted formal studies to conclusively determine the cause. But Callahan reached his conclusion based on the process of elimination and studies by researchers elsewhere.
He believes gypsy moths or drought would cause more widespread damage. Because the moths fly, their destruction wouldn't be limited to the roadside. An infestation of the early 1990s killed trees on entire hillsides, but just 100 feet into the forest along the turnpike, the trees are fine, Callahan said.
Diesel exhaust affects the entire turnpike, but the dead trees are found only in the most heavily-salted region, he said.
The spiky growths on the trees indicate salt damage, but further studies would be needed to conclude that, said Bill Elmendorf, assistant professor of urban forestry at Penn State University's School of Forest Resources.
"The witches' broom is the result of multiple deaths," he said. "Foliage is being killed back, growing back, killed back and then growing again."
The symptoms are similar to those of a dying stand of birch trees along the main highway to Lake Placid in Upstate New York.
For three years, Tom Langen, a biologist at Clarkson University in Potsdam, N.Y., and other researchers have studied the birch trees for the New York Department of Transportation, looking for a cause of their declining health. Langen is preparing to publish results pinpointing road salt as the cause.
"The infertile soil and direct stresses caused by the deposition of road salt on the leaves and branches caused the trees to die," said Langen, whose team suggested spreading less salt or substituting calcium magnesium acetate, which also melts ice, as solutions.
The Pennsylvania Turnpike Commission has considered those options, Stewart said. But calcium magnesium acetate costs $3,000 a ton, compared to the $40-a-ton for rock salt. Lowering the speed limit might lessen the mist, but would be difficult to enforce, he said.
The commission tries not to over-salt, even fitting trucks with computer sensors that limit the salt scattered on roads to what is needed, Stewart said.
The dry and dead trees are at a greater risk for fire, falling and insect infestations, Callahan said. But crews haven't removed them because they block the salty mist from coating healthy trees growing behind them.
Removal is also expensive. Timbering healthy trees could bring in $1 million to $2 million, but these trees likely wouldn't be marketable and the state would have to pay the bill. The cost to remove them and plant salt-resistant trees "far outweighs" any risk the trees pose, Callahan said.
"I hate to say it, but it's dead trees or dead people," Callahan said. "If they don't put the salt down, the road would get very icy."
The Laurel Highlands in Fayette, Westmoreland and Somerset counties attract hundreds of thousands of people every year for outdoor recreation, said Julie Donovan, spokeswoman for the Laurel Highlands Visitors Bureau. Even the stretch of turnpike "is particularly beautiful with the farmland and the forest."
"It's unfortunate that we have this blight," she said.
Additional Information:
Details
These species of trees are resistant to salt:Horse chestnut White ashBlack walnutColorado spruceWhite poplar
These species are intolerant of salt:
Sugar maple Douglas firHemlockRed mapleWhite pine
