Meet the beetles
Jan Burke recalls traveling over Independence Pass and thinking “uh-oh” shortly after she transferred to the White River National Forest a couple of years ago.The east side of the pass was thick with lodgepole pine trees that looked like they had been doused in fire retardant. The trees’ needles had turned a telltale rust color that signals a mountain pine beetle invasion.Burke, a silviculturist for the U.S. Forest Service, was initially concerned that it was just a matter of time before the destructive insects jumped the Continental Divide and crossed from the Pike National Forest on the Twin Lakes side of the pass to the White River National Forest on the Aspen side. Pests, after all, recognize no boundaries.
An outbreak of mountain pine beetles has transformed many of Colorado’s national forests in the last decade. An outbreak of the insects hit in the mid-1990s and intensified in the drought of 2002-04.”In 2006, this forest insect infested over 660,000 acres in the state, up from 500,000 acres in 2005,” said a report on forest health released by the Colorado State Forest Service earlier this year.This epidemic has broad implications for Colorado, ranging from the threat of wildfire to potential effects on tourism and water quality.”Nobody believed this infestation was going to be this big,” said Burke.Eagle, Summit counties hit hard
The epidemic shows no sign of abating. The insects will eventually exhaust their own food supply. Short of that, nothing will stop their destructive progress, said Burke.Within two or three years, Colorado will experience a “virtual loss” of all mature lodgepole pines, she said. By a virtual loss, she means 90-plus percent of the lodgepole that is 7 inches or more in diameter will be dead.The outbreak will inevitably spread to the Roaring Fork basin, Burke said. But the Forest Service’s research indicates the destruction won’t be nearly as severe in Pitkin County as in other mountain counties to the east.A map contained in the state forest service’s study on forest health shows how Pitkin County has mostly dodged the pine-beetle bullet. A long, narrow patch of green representing the state’s lodgepole pine coverage starts in the mountains by the Wyoming border and stretches down to Salida in Chaffee County. The line grazes Pitkin County’s eastern edge. Other spots representing lodgepole concentrations dot the Maroon Bells-Snowmass Wilderness southwest of Aspen and the Collegiate Peaks southeast of Aspen, but Pitkin County clearly hosts a diversity of conifer species.Neighbors to the east aren’t as lucky. Huge swaths of lodgepole forest have already been devastated in Eagle, Summit and Grand counties by the mountain pine beetle. The drive along Interstate 70 has become almost surreal because forest areas commonly called “evergreens” are not, in fact, green. Large swaths of forest are rust-colored. In some spots, graying skeletal trunks remain where the needles have fallen to the forest floor.”We’re not going to look like Summit County, at least not from mountain pine beetle,” said Burke.
The Roaring Fork basin, which includes the Fryingpan and Crystal valleys, doesn’t have as many lodgepole pines as other parts of the state, including just over Independence Pass, Burke said. And the lodgepole in Pitkin County tends to have greater age diversity.That is critical for forest health. Greater diversity equates to a healthier forest because not all trees are as susceptible to disease, insects or natural mortality at one time.Most of Colorado’s lodgepole forests ran into trouble after fire and logging claimed most of the pines in the late 1800s and early 1900s.”As a result, many of these forests are filled with trees of roughly the same age, from 100 to 150 years old,” said the state forest service report.
So mountain pine beetles won’t hit Pitkin County as hard as Summit County, but Pitkin County isn’t completely out of the woods. Older, mature stands of lodgepole exist and are threatened.The 2002 White River National Forest Plan, which examined existing conditions and set management strategies, noted that data had been collected on the health of 10,500 acres of lodgepole pine forest in the Upper Fryingpan drainage, some 30 miles east of Basalt. About 46 percent of those acres had a moderate-to-high risk level for a mountain pine beetle infestation and another 3 percent was judged as high-risk.In addition, Burke believes the Roaring Fork Valley will be hit harder by another pesky insect, the spruce bark beetle. Spruce trees cover a bigger part of the Roaring Fork basin than lodgepole pine.Spruce trees line the hills around Ruedi Reservoir and blanket the slopes of the Upper Fryingpan Valley. Popular hikes to Sawyer Lake and Granite Lakes climb primarily through groves of mature spruce.About 78 percent of the spruce forest in the Upper Fryingpan drainage was assessed in 2002 as being at moderate-to-high risk for spruce beetles with another 3 percent as high-risk. WHY?
The Forest Service has a map that shows the extent of the pine beetle and spruce beetle destruction in the Colorado mountains from 2001 through 2006. A blood-red shade shows the extend of the damage. It’s startling to see. Summit and Eagle counties are covered in the blood color. Pitkin County has patches along the Fryingpan Valley and in places like Richmond Ridge south of Aspen.A larger chunk of infected areas shows up in the Maroon Bells-Snowmass Wilderness between Mount Sopris and Capitol Peak. An even bigger splotch dominates the map southwest of Sunlight Mountain Resort, the ski area outside of Glenwood Springs.That area shows the Baylor Creek blowdown, a part of the forest that was hit by an intense storm in 1999 that knocked down trees on 3,000 acres on the Pitkin and Mesa county line. Spruce trees were the primary casualty.The dead and damaged trees became a smorgasbord for spruce beetles.”Because they primarily affect more remote high-elevation forests, Colorado’s current spruce beetle outbreaks are not as well known as the mountain pine beetle epidemic,” said the state forest service report. “However, older Engelmann spruce forests near Carbondale, South Fork and from Steamboat Springs north to the Wyoming border have experienced extensive mortality from spruce beetles.”
Burke suspects that the Roaring Fork basin could see an outbreak emanating out from Baylor Park. Imagine an ink spot on a map that grows to cover more terrain as more ink is added.”There is the potential to lose our mature spruce here, but it’s not going to look like Summit County,” Burke said.Different beetles, similar resultsPine beetles attack live, mature trees. Females attack a tree en masse, overwhelming its defenses. They bore into the bark, then dig tunnels between the bark and wood where they lay their eggs.The larvae spend the winter under the bark, gnawing away. They turn into pupae in summer, then fly as adults in late summer and start the process all over.
The green needles of the doomed lodgepole pines turn from yellow to green to rust. The needles fall off after a year or two, Burke said.Spruce beetles follow a similar cycle, although the duration is two years rather than one. The needles of doomed spruce trees fall off while they are still green, making it hard to detect infested trees from the aerial surveys the Forest Service undertakes to assess the health of the 2.3 million-acre White River National Forest.Burke said spruce beetle epidemics typically hit every 100 to 200 years compared to 10 to 15 years for mountain pine beetles. Both beetles are always present in the forest; their numbers can balloon as the result of both human and natural disruption. Warm temperatures and the uniform age of the lodgepole pine forests sparked the latest mountain pine beetle infestation. Spruce beetles need something to trigger an outbreak.When an event like the Baylor Park blowdown occurs, spruce beetles get their opportunity. They proliferate in the downed, dying and dead timber. Their numbers swell to the point where they start to attack and overwhelm live trees. They tend to target trees more than 7 inches in diameter, Burke said.The beetles pose a threat to the entire spruce forest in the Roaring Fork basin because their population has swelled so drastically in Baylor Park, Burke said. From Baylor Park the beetles are expected to spread out as they look for new food sources. A legendary spruce beetle epidemic in the Flat Tops area north of Glenwood Springs in the 1950s ended only after a sustained cold spell. (see related article)
Outside of the Baylor Park blowdown, live trees are now being attacked by the spruce beetles. Some are grand old trees 36 to 42 inches in diameter and 100 feet tall.”I hear constant conversation that we aren’t doing anything,” Burke said. “It’s absolutely not true.”Salvage timber sales have removed 30 million board feet from the area, she said. The sales are organized by the Forest Service and bids are awarded to logging contractors.The first sale in Baylor Park didn’t take place until 2006, seven years after the blowdown occurred. By then, the population had grown to the point where beetles were attacking live spruce and spreading fast.If a timber sale is undertaken within a year or two of a blowdown, dead trees can be removed and live trees can be thinned to create a buffer, slowing the spread of the beetles. The Forest Service’s action was delayed at Baylor Creek by a fight with conservationists. A coalition of environmental groups filed a lawsuit to rein in what they saw as an overambitious timber sale.
In many parts of the national forest around Aspen, nature will be allowed to take its course, even if it means the loss of thousands of acres of trees to beetles. The Forest Service does not allow logging in wilderness and roadless areas. The agency is constantly assessing whether or not timber-management projects are needed to reduce chances of a beetle outbreak, Burke said, but all such projects are subject to lengthy environmental-approval processes. Infestations of mountain pine beetles and spruce beetles have the potential to affect everything from fire danger to tourism in Colorado. Large swaths of dead or dying forests aren’t particularly scenic. Trees will really start to rot about five years after they die, and they typically fall to the ground in about 10 years, Burke said. The fallen timber can send the fire threat soaring. It is unclear how all of those dead trees will affect the ability of mountain slopes to hold snow, Burke said, and how spring runoff might be altered.
Foresters expect the lodgepole and spruce forests will be replaced in regeneration by aspen trees. It takes roughly 90 years for a pine to grow to 7 inches in diameter, Burke said. An aspen can growth 3 to 6 feet per year. Dormant root systems of aspen trees can be brought to life after an opening of the forest canopy.But even aspen trees have fallen on tough times.”For the second year in a row, unexplained aspen decline occurred in western Colorado [in 2006],” the state forest service reported. About 138,000 acres were dead or in decline.”Despite many on-site inspections, experts have not determined what is killing the trees and their root systems,” the report said. “Common culprits such as animal grazing and conifer encroachment are not responsible for this ongoing die-back.”Scott Condon’s e-mail address is email@example.com
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