"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."

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E-mail: bau@desnews.com