Up on the slopes of Mount Hood, legions of trees are in their death throes.
Needles are dropping off the bushy pines, turning them into bare, wizened fingers. Bruce Hostetler, a U.S. Forest Service entomologist, shaves the bark off one with a hatchet, exposing the culprit: squirming, white, bark beetle larvae. Young bugs the size of rice grains are chewing through tissue that carries nutrients up the tree.
The lodgepole pine, and many more, will starve, die and probably burn up in wildfires.
Bark beetles aren't new here, but suddenly they're biting down like mad. Experts estimate, conservatively, that beetles killed 145,000 trees in the Mount Hood National Forest last year, and as many or more this year. It's death on a scale that hasn't been seen in the forest for 50 years or more. Nearly 1 in 10 acres holds dead or dying trees.
It's the final chapter in a natural cycle streaking the Cascade Range with great swaths of dead, reddening forest. Statewide, beetles went after 570,000 acres of forest in 2003 and 710,000 acres in 2004 -- together an area seven times larger than Crater Lake National Park.
The little insects are nature's recycler, killing aging trees and making way for wildfires to clear room for new forests. But our drive to put out wildfires, plus subtle climate changes, may have a hand in today's beetle boom.
And there's a bigger picture: The bugs are doing damage on a staggering scale across the country and in Canada. Scientists suspect those outbreaks may be tied to global warming, as temperatures only a few degrees higher help more beetles survive in places where cold once knocked them back.
"It's being increasingly recognized that there is a massive regionwide, if not continentwide, beetle problem cropping up, and that it is a possible consequence of climate change," said Ronald Neilson, a U.S. Forest Service climate researcher in Corvallis.
Across Arizona and New Mexico, sturdy pinyon pines have succumbed to beetles never known as a problem before. The largest pine beetle outbreak in North American history has killed British Columbia forest equal to almost a third the land area of Oregon. It used to be too cold for beetles; now, they're expected to kill four of every five interior lodgepole pines by 2013.
It's not as clear that warming is at work in the Cascades. Temperatures aren't as cold here to begin with, and beetles are a longtime resident. The forests are ripe for beetle attack, so the attack is not a surprise.
But warming and the kind of dry years the Northwest has seen lately put trees under greater stress and accelerate a beetle onslaught, experts say.
"There's probably some contribution warming is making; we just can't put our finger on it," said Andy Eglitis, a Forest Service entomologist based in Bend. He has watched beetles kill wide reaches of the Deschutes and Fremont national forests on the east side of the Cascades.
Older trees vulnerable
The table has been set for beetles mainly by the passage of time.
Their prime target is skinny and short-lived lodgepole pines that grow at higher altitudes and burn up in big fires. Many lodgepoles on Mount Hood took root after widespread fires nearly a century ago. They're now perhaps 80 or more years old, about as big as they're going to get, and face rising stress as they crowd one another for light, water and nutrients.
A core of wood from one tree tells the story: It started out growing quickly, putting on thick new rings of wood each year, but in recent decades its rings have become paper-thin. It devotes all its energy to simply hanging on.
"The first thing to go is resistance to insects and disease," Hostetler said.
These trees have become what foresters call "beetle bait."
Stressed trees emit chemical signals that lure beetles like perfume. Adult bugs take flight in summer, boring through the bark of the biggest trees they find to lay eggs. They release their own chemical beacons to rally others in a mass attack. Healthy trees fight them off with gobs of sap, but aging, strained trees cannot.
"When you get in outbreak mode, with literally thousands of beetles, the tree's just overwhelmed," Hostetler said, under a pine losing its green hue. "This tree's dead. It just doesn't know it."
Hidden larvae that feast on the tree's golden grain etch intricate but deadly patterns into the wood.
Usually beetles kill a tree within a year and move on to the next one. They multiply as they spread. The dying trees merge into the sprawling patches of red forest now scattered across the eastern flanks of Mount Hood.
Hard-hitting outbreak
Oregon has endured major beetle outbreaks before in the Cascades and Blue Mountains, but this one is hitting hard, especially around Mount Hood.
Whitebark pines on high ridges, already hammered by a foreign fungus called blister rust, are being killed by beetles. Almost all the lodgepole pines around Olallie Butte at the south end of the Mount Hood National Forest have died. Another form of bark beetle, the fir engraver, has gone after Douglas firs across the forest. Ponderosa pines, especially dense stands planted after clear-cutting decades ago, are at risk, too.
It might sound savage, but it's the way the forest works. Foresters in decades past tried halting beetle outbreaks by cutting down infested trees and burning them, or spraying DDT and other chemicals, but never succeeded.
"There's not a single shred of evidence you can control them," said Scott Hoffman Black, an insect expert and executive director of the Xerces Society, an insect conservation group based in Portland.
Mount Hood National Forest managers won't even try. They're focused on trying to salvage and thin dying trees -- particularly near homes -- so fires likely to burn through them are less severe. The beetles themselves probably will spread until they run out of vulnerable trees, silviculturist Nancy Lankford said.
They may be approaching that limit now, she said.
Forest managers long tried to keep fires from sweeping through aging stands, but that may have compounded the problem. Blazes might have split the landscape into a patchwork of varying ages, some inviting to beetles but others not.
Today, however, the beetles have vast, unbroken swaths of forest, so they can spread and multiply nonstop.
Thinning can slow beetles
Northwest loggers often weren't interested in lodgepole pines because their small size has little commercial value compared with bigger ponderosas or Douglas fir. Some national forests tried selling infested trees for salvage but got no takers, Lankford said.
That's changed now, she said, and loggers are salvaging some dying trees in accessible areas -- often for firewood.
Forest officials are employing loggers to thin out crowded ponderosa pine plantations on the east side of the Cascades to make them less vulnerable to beetles and fires. There is good evidence that thinning can discourage the spread of beetles in ponderosas, though not so much in lodgepoles, Hostetler said.
Ponderosa pines can withstand occasional fires, not burning up as lodgepoles often do.
Trees in more natural stands have a better chance of fending off beetles, because trees are stronger and other species that prey on beetles also find a home, Black said.
"There's a lot of them out there trying to do their job," he said.The Oregonian
