From the Uinta Mountains on the Wyoming border to Dixie National Forest in the south, Utah's spruce trees are dying. Some forests may not return to their previous condition for hundreds of years.
Until recently, few vistas were as splendid as those unfolding along the Skyline Drive. Unpaved except for one small segment, the route wends for 87 miles along the mountainous backbone of central Utah, from Tucker to I-70. It is praised by one bicycling guide on the Internet as "Utah's highway to heaven." Driving or biking along the edge of the Wasatch Plateau, visitors could view and camp beneath beautiful stands of dark green Englemann spruce.
But no more. Now, these "evergreens" are turning orange and red. In Manti-LaSal National Forest alone, where most of Skyline Drive is located, an estimated 75,000 acres of spruce trees are dead or dying.
The forest will come back — but not for at least 300 years.
The die-off is "pretty extreme," said Diane Cote, Manti-LaSal's forest silviculturist. "This and what has happened in Alaska are some of the worst we've ever documented."
Immediate cause of the kill is a spruce beetle infestation that spread like wildfire because of drought-weakened trees. But from a longer standpoint, the spruce is aged, nearing the end of its life, and this may simply be part of nature's cycles.
Manti-LaSal isn't the only Utah forest hit by the spruce death. Fishlake National Forest may be next, and Dixie National Forest seems to be on the beetles' menu.
Wayne Padgett, forest ecologist working for Wasatch-Cache National Forest, based in Salt Lake City, said the agency has noticed a spruce beetle kill on the Uinta Mountains.
He was on Bald Mountain recently looking into the High Uintas. "We have a lot of gray trees out there, which means that they're dead," he said.
On the Upper Provo River watershed in the forest's Kamas District, bug kills are happening, and "not just spruce," Padgett said. "We've got beetles killing spruce, fir and pine."
Vulnerable trees
Speaking during a telephone interview from her office in Ephraim, Cote explained that in Manti-LaSal, spruce beetles are a naturally occurring pest. In a normal spruce population, if a tree is failing or damaged — by lightning strike, for example — "the bugs can sense a weakened tree and go and attack and kill it," she said.
Nature is taking out the weak and infirm, though the forest survives.
Sometimes, when many trees are old, crowded together and stressed at the same time, a triggering event can have more shocking ramifications.
In 1983-84, when precipitation was so heavy that whole mountainsides began to slip, a 1,000-acre landslide occurred in Twelve Mile Canyon, toward the south end of Manti-LaSal National Forest.
"It knocked down a whole bunch of spruce," weakening others, Cote said. At the time, forest officials had been preparing a timber sale of trees that were being attacked by beetles. Agency experts had prepared the environmental documentation and marked the site prior to the sale.
"The slide came along and took out the road," she said. "They had no way to get in there."
They decided to rebuild the road and resume their project, but that took some time.
Meanwhile, the bugs sensed all the downed and weakened trees, she said. "The bugs went into this damaged material, and their population just exploded."
The spreading beetles have killed all of the spruce from the southern end of the forest to Fairview Canyon about 50 miles away.
"It keeps moving north. It hasn't stopped," Cote said.
At the same time, the beetles have moved south onto the Fishlake National Forest. And Dixie National Forest has a beetle problem, too, apparently an entirely separate outbreak.
Aging forests
The age of the forests may be to blame. The last time a big die-off happened may have been about 300 or 400 years ago. Now, this generation of trees is vulnerable.
Contributing to the strength of this cycling effect is that Utah's Englemann spruce grow at high elevation.
According to the "Atlas of the Vascular Plants of Utah," the Englemann spruce grows between an elevation of about 7,900 feet and 10,000 feet. At that altitude, so much snow falls that the forest tends to be spared from fires.
In addition, Englemann spruce often grow in isolated stands, not in long continuous forests that are more vulnerable to unstoppable wildfires.
The upshot is that the spruce aren't continually renewed, like many other trees. They grow slowly until they reach the natural end of their lives.
"No tree lasts forever," Cote said. Spruce seem to be able to live more than 250 years in the Manti-LaSal National Forest.
When they are weak and old, stressors like the drought, now in its sixth year, or a beetle attack may suddenly wipe out thousands of acres of trees. It's nature's recycling system.
When Englemann spruce tree stands reach 180 or 200 years of age, generally "they get into a condition where the bugs go, 'Oh gee, supper!' " she said.
Death and life
Spraying to protect trees against beetles is difficult because the infestation is so dense.
"There's so many bugs hitting these trees that they can't win," she said. Agency workers can't move fast enough to get ahead of them.
Forest workers spray protective chemicals on trees in some campgrounds, trying to save "high-value" trees where the public visits. But if a tree is tall, they can't spray all the way to its top, and the bugs still get to it.
Logging to get rid of nearby infested trees can save some stands. But that can't stop the spread of the spruce mortality.
"We're losing almost everything over 16 inches" in diameter, she said. About 90 percent of trees more than 10 inches in diameter are going, also.
But small trees, young ones that grew after recent lightning strikes opened a place, have a better chance.
"While it is a catastrophic effect on spruce . . . , this is normal, and the spruce will recover in time."
How much time?
The spruce could stand, dead, for a quarter-century before it falls. About 100 years after the tree falls, it will have moldered into the soil. But that doesn't mean new spruce trees will be growing up yet.
This species needs bare mineral soil with shade to reseed itself. With the spruce forest down, shade will be scarce. That environment is more conducive for the growth of subalpine fir.
For a century or so, "we'll probably go through a cycle" in which subalpine firs grow, die, catch fire because of all the dead spruce, and grow again.
Gradually, enough firs will grow that seeds from the scarce remaining spruces will find a place to take hold.
"Over time, probably 300, 400 years," Cote said, "we'll have a forest like we have now."
E-mail: bau@desnews.com