CHEYENNE, Wyo. (AP) -- Slash piles surround the parking area on Pelton Creek Road in the Medicine Bow National Forest, southwest of Laramie near the Colorado border.

Grant Frost, a terrestrial habitat biologist for Wyoming Game and Fish, inspects a tree, looking for telltale signs of beetles.

The tree looks alive, but it probably won't be for long. The brown cadavers of lodgepoles past stand among smaller, greener pines, testifying to the unavoidable truth: Change -- big change -- is coming.

"The general feeling is this will end when the food supply runs out," Frost says.

Looking out on the variegated landscape of greens, reds and browns, two things become clear.

One: This is one of the biggest ecological changes we have ever seen. It's daunting and scary and -- for the experts -- exciting all at the same time.

A plague of beetles, including one that just now is taking its turn, is cutting a swath through the national forests in north-central Colorado and into Wyoming. At the low end, it's possible that just 10 percent of large lodgepole pines will be left.

It's also possible that they all will be gone.

But other and smaller trees suddenly are being chewed up as well. Where that leads remains to be seen.

The implications of all this are impossible to pin down, but they could affect each and every one of us.

They possibly include an increase in global warming, large-scale wildfires and big changes in water supply.

And then there is this fact: These forests will never look the same again.

Two: This change is inevitable. Try as we might, there's no stopping it.

It's no secret that pine beetles have slowly been munching away at the national forests for years.

It's also no secret that it's part of an enormous ecological process at work.

And it's no secret that, in the end, that process will benefit the forests.

But what does that look like in the meantime?

Right now, the Northern Rockies, Southwest and dry forests of the Northwest have nearly 8 million acres of trees affected by bark beetles.

The spread has agencies preparing for the worst. Even with the last two moist years, there is no indication that the beetles' appetite has been sated.

The Forest Service expects that about 90 percent of the lodgepole pines 8 inches and larger in diameter will be dead.

Smaller trees also are being infested on a smaller scale. But now a new bug -- the twig beetle -- has started popping up in stands that have been infested with the mountain pine beetle.

"Starting with this twig beetle, we are losing some younger trees too," says Mary Ann Chambers, spokeswoman for the Rocky Mountain Region Bark Beetle Incident Management Team.

She says trees 5 inches in diameter are now commonly being killed. They are even seeing mortality in some trees 4 inches in diameter.

In addition, there has been an increase in beetle activity in ponderosa pine.

"It's kind of doing what we were afraid it would do," says Bob Cain, entomologist for the U.S. Forest Service's Rocky Mountain Regional Office.

Ponderosa pine tends to be more varied in terms of spacing and age, unlike lodgepole, which is typically uniform in size and age.

"I'm hoping that we'll see less-dramatic activity in ponderosa pine," Cain says.

The variation in these stands makes the future much harder to predict.

"Our crystal balls aren't that good," he says.

It's important to note that there are many different types of beetles converging in one place.

There is the mountain pine beetle, the most aggressive of the bunch. There's the Douglas-fir beetle, the spruce beetle and the western balsam bark beetle.

So the addition of another beetle is not entirely surprising.

"The mountain pine beetle is creating habitat for other beetles," Cain says.

He says there are many things that follow in the wake of the mountain pine beetle: three-toed woodpeckers, long-legged flies, parasitic wasps.

But this particular twig beetle is nothing to ignore either.

Typically the mountain pine beetle will feed on the main trunk of the tree, leaving other parts for other bugs, such as the twig beetle.

"But there are so many of them, they're coming into the smaller trees that the bark beetles aren't attacking," Cain says.

He says they are seeing trees only 2 to 3 inches in diameter showing signs of twig beetle. In some places, this is a good thing because it thins out young stands. But in other places, twig beetles are taking out entire stands.

There is some good news to all of this.

Many species actually will benefit from the change in forest, such as elk, woodpeckers and olive-sided flycatchers. These species typically depend on open shrub and grass-dominated habitats.

"These increases in animals may be short lived, and then things will kind of come back down to normal," says Bob Lanka, public information officer for Game and Fish.

Other species will see temporary declines.

On the losing end will be the pine marten, blue grouse, red squirrels and boreal owl, which will experience short- to midterm losses in population.

Mike Snigg, regional fisheries supervisor for the Laramie region, says the change in forest could have similar effects on fisheries.

Downed trees and woody debris provide good habitat for fish. But too many trees can create log jams, altering the course of a river. Additionally, the threat of fire, soil sterilization and erosion pose threats to aquatic populations.

The increasing number of dead trees also is an issue of public safety.

"The big movement is to get the hazard trees off the roads and trails," Chambers says.

In Wyoming alone, there are 611 miles of road, 51 miles of trail and 139 developed recreation sites affected by hazardous trees.

But in the Medicine Bow-Routt, White River, Arapaho and Roosevelt national forests (the epicenter for the beetle, in north-central Colorado and spreading into Wyoming) 911 miles of trails, 3,467 miles of road and 21,455 acres of developed recreation sites have been affected.

"We're going after those areas where people congregate and where they recreate first," Chambers says.

She says people need to take caution out in the forest. As dead trees age, their roots rot, causing them to fall.

"Everybody needs to be careful out there: Watch out for where they camp, where they park, where they're walking as far as dead trees go. Stay out of the forest on really windy days," she says.

Another priority is power lines. The Forest Service in Wyoming recently completed an environmental assessment looking at removal of trees along 69 miles of distribution lines.

Water supplies also have the potential to be impacted by the die-off.

Matt Hoobler, North Platte River coordinator for the Wyoming State Engineer's Office, says trees are an important factor in snow pack, and many Western cities depend on snowpack for water supply.

He says dead trees don't capture snow the same way live trees do, so there could be a shift in the amount of snowpack.

Once spring comes, there will not be shade to keep the snow cool, so the timing and rate of snow melt could change, affecting riparian areas, fisheries, agriculture and municipalities.

In a statement before the Subcommittee on National Parks, Forest and Public Lands and the Subcommittee on Water and Power on June 19, Rick Cables, regional forester for the Rocky Mountain region, said the issue of water is of national importance:

"Forest Service hydrologists estimate that forests of the Rocky Mountain Region contain the headwaters for much of the western United States; people in 177 counties in 13 states rely on water from the national forests of the Rocky Mountain Region. Thirty-three million people live in these counties."

And while agencies know things are bound to change, possibly drastically, Hoobler says it's hard to pinpoint exact changes.

"There's so much unknown," he says.

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