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.