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Tough to be a tree: Southwest Colorado’s forests are stressed

Drought, wildfire, bark beetles pose collective long-term threat

Drought, wildfires, beetle infestation – forests across the San Juan Mountains seemingly can’t catch a break in recent years.

“It’s a tough time to be a tree right now,” said Dan West, an entomologist with Colorado State Forest Service. “We’ve never seen anything like this before.”

For the past few years, Southwest Colorado has been gripped in a prolonged drought.

Snowpack in winter, the region’s most important water source, has been erratic and more often than not, has not been hitting historic averages. To make matters worse, snow has been melting off earlier than usual in the spring.

For at least the past four years, the monsoon has failed to bring moisture in summer, resulting in an even more parched forest floor. And, the region as a whole has experienced warmer than average temperatures.

Needless to say, trees in the forest are stressed, and they are less resistant to fighting threats like the bark beetle or wildfires.

“Without moisture, it puts the trees at a disadvantage,” said Bob Cain, regional entomologist for the U.S. Forest Service.

Beetle kill

In Southwest Colorado, the spruce beetle epidemic started on Wolf Creek Pass in the late 1990s and took off around 2004. Now, the beetles have worked west through the Weminuche Wilderness, north toward Silverton and Telluride.

Though the beetles are native to the land, the insects’ toll has been exacerbated as drought, warmer winters and dense forests have created the perfect conditions for an outbreak that has spread at an alarming speed.

It takes about a year to see the effects of a bark beetle infestation, local foresters say, so they won’t know how bad the spread was in summer 2020 until next year.

At last count, the spruce beetle had torn through nearly 1 million acres of the Rio Grande and San Juan national forests, which, combined, total about 3.6 million acres, though not all of that land is spruce forest.

And there just seems to be no end in sight, Cain said.

In the 1950s, a bitter cold snap that brought minus-50 degree temperatures ended a beetle outbreak in the White River National Forest in northwest Colorado, but temperatures haven’t reached that low in years, Cain said.

West added that studies in the 1980s found about 20% of beetles used to die over the winter.

“We don’t see that anymore,” he said.

But perhaps more important, Cain said, is the fact trees have been weakened because of drought, and are less able to fight off an infestation. And it appears in recent years, this could be the new normal.

While the spruce beetle has garnered the most attention for tree mortality across the forest, Cain said there’s a pesky beetle for just about every tree species, and he fears these other insects may take off as drought conditions persist.

“There’s a lot of beetles out there, and they’re continuing to expand,” he said.

Reforestation challenges

Gretchen Fitzgerald, a forester for the San Juan National Forest, said reforestation projects on public lands showed high mortality this year, a result of bone-dry conditions on the landscape.

As another layer of complication, a late frost in June wiped out this year’s cone crop for nearly all tree species, which is expected to affect natural regeneration, Fitzgerald said.

“With all these fires, we’ve been trying to get our seed banks in order so we can respond with reforestation projects,” she said. “The frost really impacts our ability.”

Gretchen Fitzgerald, a forester with the San Juan National Forest, said a late frost in June killed nearly every tree species’ cone crop this year, which could affect natural regeneration in the forest.

Indeed, wildfires have plagued Colorado this year, with the Cameron Peak and East Troublesome fires becoming the first and second largest wildfires in state’s recorded history, respectively.

And a late season wildfire west of Silverton in the San Juan Mountains showed that even high elevation forests are at risk. The Ice Fire, as it came to be known, was the first fire to threaten the town of Silverton in more than 140 years.

“It’s really just a sign of the times and the cycle we’re in,” said Michael Remke, a forest health research associate with Mountain Studies Institute.

Cause for optimism

Despite all this, there is reason to be optimistic, Remke said.

Forest ecologies are resilient, and while conditions may not return to the way things were, they do adapt and change.

Wolf Creek Pass, for instance, was devastated by the spruce bark beetle outbreak in the early 2000s. But in years since, new species have taken hold and exploded with new life on the forest floor.

“Yeah, it’s (bark beetle tree kill) in your face ... but the reality is the understory regeneration,” Remke said.

A fire west of Silverton last month has foresters concerned that persistent drought has created conditions for wildfires in high elevations at late times in the year.

Over on Missionary Ridge, north of Durango, a 2002 wildfire ripped through more than 70,000 acres. But 18 years later, trees are spreading back on the landscape, both through natural means and regeneration projects.

“Forests operate on such long time scales,” Remke said. “Give it some time. These landscapes are resilient.”

One other bright spot, Remke said, are all the new partnerships and working groups that are coming together to think of ways to respond to issues like change or areas where wildfire poses a high risk to homes.

“We’re probably going to come up with innovative solutions to these new challenges,” he said. “I have a lot of optimism.”


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