Pine beetles are changing the landscape of Rocky Mountain National Park.
By Kelly Bastone
Visitors to Rocky Mountain National Park are seeing red. The pine trees that once gave these peaks a velvety green cloak are increasingly taking on a strange, rust-red color as they succumb to an unprecedented onslaught of bark beetles. For most visitors, encountering huge swaths of dead, red trees produces a shock they don’t soon forget.
“People are surprised and sometimes even angry to see so many trees dying,” says Kyle Patterson, Rocky Mountain’s public information officer. Bark beetles have infected 50,000 acres—about 19 percent of the park. Tens of thousands of pines have died since 2002, when the park observed the first indicators of the current beetle outbreak, and more losses are expected. In fact, the park represents just a small portion of a larger beetle epidemic extending from Canada to New Mexico.
The size of a grain of rice, bark beetles kill mighty conifers by tunneling under their bark and laying eggs, which hatch into larvae that feed off the trees’ phloem (an inner bark layer that transports nutrients). One species, the mountain pine beetle, also carries a fungus that stains the sapwood blue as it chokes off water to the upper branches.
But these pests aren’t foreigners. All 17 species found in Rocky Mountain National Park are native insects, and like forest fires, they play a valuable role in the ecosystem. Several times a century, beetle populations soar to outbreak proportions, killing large numbers of trees and ultimately improving forest health. This time, though, the beetle epidemic is bigger than anything on record.
One reason is the recent drought, says Brian Verhulst, a supervisory forestry technician at Rocky Mountain. Ten years of below-average precipitation left trees too weak to “pitch out” the invading beetles (strong, healthy trees use sap to keep them out). Another factor is how uniform forests had become after nearly a century of fire suppression: Pure stands of feeble old trees succumb to beetles more readily than diverse forests. Finally, warmer-than-average temperatures in recent years have stimulated beetle reproduction and let larvae thrive throughout the winter. “Cold snaps curtailed previous beetle outbreaks,” Verhulst explains, “But the park hasn’t experienced the consistently cold temperatures that used to be seen here.”
The mercury’s effect on bark beetles has prompted some observers, including U.S. Forest Service research entomologist Barbara Bentz, to investigate whether rising temperatures would give beetles a leg up. Bentz has studied temperature’s effect on bark beetle populations for more than 15 years, and her research helped build a mathematical model that predicted increasing global averages would produce a big-time beetle outbreak—just like the one now underway.
“I don’t think the current outbreak is purely the result of global warming,” Bentz says. But she does believe that its staggering proportions—resulting in waves of dead, red trees—indicate something may be out of balance.
Verhulst and other park officials agree that climate likely plays a role in the current beetle bonanza, though the exact influence remains inconclusive. What’s certain is that massive numbers of dead and dying trees present new challenges to a park unit that attracts nearly 3 million visitors a year.
Stopping the beetles is practically impossible, so rather than trying to save its trees, park officials are trying to minimize the potential for a messy, dangerous aftermath. Interpretive panels at the Kawuneeche Visitor Center and at various viewpoints help visitors understand the dramatic changes they’re witnessing. Similar information is also published in the park newsletter. And rangers urge visitors to be mindful of dead and dying trees as they hike and camp, particularly during high winds. “It’s become part of our basic safety message,” says Patterson.
Certain high-value trees are sprayed with carbaryl, an insecticide that must be painstakingly applied to the bark from top to bottom. Even then, such measures don’t always protect trees from beetles: The park sprayed Timber Creek Campground’s tall, stately lodge poles every year, but the measures failed to ward off the onslaught, and now, in order to protect campers from toppling timbers, two of the campground’s three loops are closed.
Elsewhere, the park is cutting hazard trees near parking lots, trailheads, and other high-traffic areas: Ten thousand trees were felled in 2008, and the park expects to remove 500,000 more over the next five years. The biomass is then incinerated in an air-curtain burner—a portable, enclosed furnace that contains the blazes and emits very little pollution.
The park is also employing open, pre-prescribed fires to help reduce the likelihood of widespread conflagrations—perhaps the beetles’ most threatening legacy. Lots of dead, dry trees load forests with fuel, particularly once the needles drop and accumulate on the ground. Campers may even be asked to forego campfires in future years; meanwhile, the park itself expects to execute an increasing number of controlled burns. Says Verhulst, “We’re going for a little smoke now, versus a lot of smoke later.”
In time, however, Rocky Mountain’s forests may actually benefit from the beetle-triggered upheaval. Wildflowers and aspen trees are already sprouting where the pines once grew, beginning a diversification process that Verhulst says is ultimately a good thing. “When fires ripped through Yellowstone National Park twenty years ago, it was perceived as a disaster, but now we see that it promoted a rich diversity of species and habitat,” he says. Bark beetles may have a similar effect at Rocky Mountain National Park. “It’s a hard pill to swallow,” he admits. “But it’s like pressing the reset button on nature.”