With autumn just around the corner, the changing leaves in the valleys and on mountainsides are beginning to provide vibrant color displays for outdoors lovers.

Thousands of evergreens are also undergoing a less-attractive transformation. The trees are exhibiting dying orange and brown needles.

It’s caused concern for residents who’ve witnessed swathes of trees being infested and feasted upon during a beetle epidemic that’s lasted more than a decade. But the Colorado State Forest Service is reassuring residents of Summit, Eagle and Grand counties that most of the trees showing orange and brown needles are simply going through a natural shedding process — because, despite their name, evergreens do not stay green forever.

“Coniferous, or evergreen, trees drop their third- or fourth-year needles each season,” said State Forest Service forester Ryan McNertney.

Old needles are less productive than newer needles, so in the fall most conifers shed old needles that aren’t contributing to the photosynthetic uptake of the tree.

“The tree can only take in a certain amount of nutrients and water each year. They are going to put that into new growth versus the old growth,” McNertney said.

The forester urged residents to take a closer look at the evergreen trees this fall. If the needles are dropping off from the inside out, that is, the needles that are closest to the trunk of the tree, this is a natural phenomenon.

“There will be green needles toward the end of the branch and brown and orange needles closer to the stem,” McNertney said.

This phenomenon is different from what happens to trees infested by bark beetles.

“With beetle infestation generally the tree is going to turn a dingy green-yellow, then it turns red and the whole tree will be dead, rather than just the inside branches,” McNertney said.

Bark beetle trees will also show other signs of attack, such as fine sawdust at the base of the tree and popcorn-shaped masses of resin on the trunk.

McNertney said there is little pine-bark beetle activity remaining in Summit County.

“I’d say in Summit County about 90 percent of the epidemic is done. There may be isolated pockets south of Blue River and Hoosier and a tree here or there in the Keystone area,” he said.

U.S. Forest Service timber manager Cary Green has been working to remove beetle-kill trees on Summit County federal land.

“We are over the outbreak or epidemic, but the mountain pine beetle will always be around in local populations,” he said.

In addition to the work private landowners and municipalities have done to remove beetle-kill trees, the U.S. Forest Service has treated about 9,312 acres of trees on federal land in Summit County, Green said. This includes about 1,759 acres treated along roads and 583 acres along trails.

“We have another 3,000-plus acres of treatment planned,” he said.

While state and federal forest agencies have worked to remove as many dead trees as they can get to with the resources they have, many more beetle-kill trees remain throughout the area. The trees that haven’t been cleared will eventually rot and fall down.

“We are seeing a dramatic increase in the amount of fallen trees,” McNertney said.

Most agencies issue safety messages about falling trees in the springtime when soil conditions are moist and weather conditions include heavy winds, but beetle-kill trees can fall at any time, McNertney said.

“It can happen any time of the year and any day of the year. You just have to be aware of your surroundings all of the time in our forests now,” he said.

Although the beetle epidemic has made its mark on the woods of Summit County — and all the way up to British Colombia — it’s not the end for our forests.

“A lot of people say it’s a dead forest. But if you look at the ground you can see aspen, and lodgepole and spruce coming in. It’s not an old forest, it’s a new forest now,” McNertney said.