Two years ago, Forest Service incident commander Wettstein did some "back-of-the-envelope math" in an effort to determine "where we are in the temporal continuum of the epidemic." Calculating from aerial survey data for northern Colorado and southern Wyoming that indicated 3.6 million acres had been affected at that time, and using a mortality rate of 100 trees per acre, he came up with a ballpark figure of 360,000,000 dead trees.

Wettstein estimated that the trees would begin to fall three to five years after the beetles were done with them, and that 90 percent would be on the ground after fourteen years. Since Colorado was already a decade into the epidemic, that meant trees were probably falling over the place. Dividing 360,000,000 trees over ten years (3,650 days), he worked out an average fall rate of almost 100,000 trees per day.

Wettstein never intended his rough estimate to be used in shaping management decisions. But the figure has acquired a life of its own.

CU researchers Jeff Mitton (left) and Scott Ferrenberg observed the beetles achieving two generations a summer. Slide show: Meet the beetles: How Colorado's forests are bugging out
Mark Manger
CU researchers Jeff Mitton (left) and Scott Ferrenberg observed the beetles achieving two generations a summer. Slide show: Meet the beetles: How Colorado's forests are bugging out
Larvae and adult beetles at work. Slide show: Meet the beetles: How Colorado's forests are bugging out
Jeff Mitton
Larvae and adult beetles at work. Slide show: Meet the beetles: How Colorado's forests are bugging out

Details

"That thing will never die," he says. "I came up with that number, and I've regretted it ever since. The regional forester picked up on it, and it started making its own weather."

Indeed. Western Bark Beetle Strategy, a Forest Service report released last year, declares that "up to 100,000 dead trees killed by beetles fall to the ground every day in southern Wyoming and northern Colorado.... In the Interior West alone, there are approximately 14,000 miles of roads, trails and right-of-ways that could be adversely affected by falling trees, as well as approximately 1,400 recreation sites." The 100,000-trees-a-day mantra has also shown up in wide-eyed news reports and has been repeatedly cited in congressional testimony, most recently during field hearings in Montrose last month on the beetle infestation sought by Colorado representatives Scott Tipton and Mike Coffman.

Many scientists tracking the current epidemic have a hard time digesting that number. They say it's based on several debatable assumptions, starting with the size of the affected acreage. Stating that four million acres have been "affected" by beetles doesn't translate into four million acres of dead trees, as is sometimes reported. An affected acre may have only a few trees hit by beetles in a given year, enough to be observed by the aerial surveys.

State forest service entomologist Stephens, who flies frequently over the kill sites, says the survey data is complex and intended to track trends, not provide precise figures. "It's a lot of speculation rolled into some basic algebra," she explains. "We have to make assumptions about how many trees per acre there are in parts of the forest, then account for what percentage the host species represents on those acres.... The biggest problem with all of this is that we don't have good figures for trees per acre for most of our forests, so to get to a figure like the number of trees impacted in 2011, we're likely to end up with the kind of number that is so far stretched with assumptions that it loses value."

Although in some areas beetle mortality could approach 100 percent, the more likely scenario is quite different. The Forest Service's own National Insect and Disease Risk Map, which uses sophisticated computer modeling to predict how tree species react to various threats, projects no more than a 25 percent mortality rate from western bark beetles over 20 million acres of forests at risk across the region. To fit the NIDRM model, Wettstein's estimate would require a density of 400 trees per acre, with a fourth of them killed. CU's Mitton points out that means trees spaced about ten feet apart — a figure that seems too high for the large lodgepole trees targeted by the beetles. If the lodgepole are intermixed with aspen or spruce trees, he notes, the actual average per acre could be far less.

There's also the matter of how quickly a dead tree falls. "They're assuming that all the trees that are killed will fall within ten years, and that's in direct contradiction to numerous studies that have been done on the longevity of snags," says Chad Hanson, director and staff ecologist of the California-based John Muir Project. "Most trees stand for considerably longer. They can stand for fifty or a hundred years."

Wettstein insists the 100,000-trees-a-day figure is a conservative one, since it doesn't take into account the green trees that, once surrounding trees are killed and fall, end up being exposed to the wind and could also be toppled. Hanson says he isn't surprised that such an off-the-cuff estimate has been so widely disseminated by the Forest Service, which he believes has a vested interest in exaggerating the scope of the problem.

"The Forest Service is very good at pointing out the portions of the landscape where the beetle mortality is highest, but it's actually a relatively small portion of the landscape," he says. "What they're saying is wildly inaccurate."

Whether the actual daily death rate is slightly higher or much lower than the hundred-thousand mark, falling trees have become a top priority for the Forest Service, which has embarked on an ambitious program to protect infrastructure and increase public safety by removing thousands of dead trees in high-use areas. Crews are thinning stands around campgrounds, clear-cutting trees that threaten power lines and roads, laboring to remove tons of dry, red-needled fire hazards in areas close to mountain subdivisions and municipal watersheds. In 2011 the agency spent close to $85 million on such efforts to "treat" 187,800 acres, including kill zones sprawled across three national forests in Colorado.

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21 comments
Leola
Leola

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Henderson
Henderson

Please read the article in full. Your comment is off the mark

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Leola

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Now   Pow
Now Pow

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Leola
Leola

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Gielsj
Gielsj

This isn't the only study on these, and it has been shown that winters are not cold enough to kill off these bugs

Anthony Beretta
Anthony Beretta

Unless the tree is dead that it can freeze easily. I've seen DEAD wood freeze yearly in the mountains of northern new mexico. So that's why I don't think temperature has a lot to do with this problem.

Bobbert
Bobbert

Nice fixation, Ranger. Lack of forest diversity? Somewhat. Lack of water? Definitely. Longer warm season? Yes. That's what I took from the experts. And experts in Entomology/Forestry are going to be as excited about their subject going up in a mainstream paper as you suggest I am about it. So, I'm not sure which of the indifferent, "who cares" comments you see coming from an expert, or anyone with a degree in this stuff.

Swampfoxcws
Swampfoxcws

So....errr...I suppose the fact that we have not allowed a fire-dependent forest to burn for a hundred years had nothing to do with it? And this climate change thing - what is the climate supposed to be doing? Staying the same? Getting colder? What? We are generally coming out of an ice age, so it is not astounding to me that the climate is getting warmer. Al Gore is making a lot of money on this deal, with his carbon footprint of a thousand city people!

Bob
Bob

Holy long-winded crapology.

Bobbert
Bobbert

Grower: I am absolutely positive that there are other researchers looking for generations of the insects of their choice. I don't doubt that every insect is a major concern of yours as a grower. However, its BS suggesting there is no story (as Phd and others suggested) in the fact that pine beetles have been observed flying for the FIRST time in the Colorado high country in May during a drought which has weakened tree defenses, setting this whole situation up as a potential epidemic...that's a story I am glad is being reported. Regardless of what the other insects are up to. Westword runs gossip pieces and bullshit blogs constantly and no one comments. But here we get a long story that hasn't been regurgitated a billion times, and people are dissing the fact that it was even reported because a small part of the story doesn't jive with their opinion on the narrowest little subject that they know anything about. I stand by my fucking point.

JB
JB

I remember as a kid seeing all the beetle kill trees that were cut down, sprayed, and wrapped in plastic to control their spreading. You could see them on the way up the canyon to Central city on the mountainsides. If this has stopped, the question should be WHY??????

Oliver Philip
Oliver Philip

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Grower
Grower

Ask any farmer and they will agree warm winters increase the yearly chances for multi generations of insects. Are you on the peer review for this article? They plan for this. I agree this is common knowledge. Further, if I planted the same corp every year during an increase of annual multi generation, or single generation, of damaging insects I would be out of business. The lack of forest diversity is the cause and the effect. Climate fluctuations ehances lack of forethought in forest management - the real cause. Examing different type of insects and multi generations of seasonal hatching proves that pine beetles are not exclusive and climate fluctuation increases are in fact common knowledge. Defending someone's thesis, in this case, proves your lack of understanding the "whole fucking point."

James Reynolds
James Reynolds

Dead fuel accumulating for the past 15+ years. Fires take off like hot cakes. You do the science.

Bobbert
Bobbert

Phd: Early beetle flights resulting in 2 generations per year, instead of 1 is not common knowledge. In fact, it goes against everything we know and accept about the pine beetle. The fact that they can lure a pine beetle with pheromones in May is proof enough. Larvae cannot be lured through the air by pheromones, and pine beetle eggs will not spontaneously grow wings in "cold winter" to be drawn to a trap. The whole fucking point is that weather changes are now allowing 2 generations per year instead of 1. You want to see this test run during the egg stage? Do you see insects cruising around when the weather is cold? Do you really think that beetles trapped using pheromones in May are less developed than the one they happened upon on Niwot Ridge in May? And what would running the experiment with "other beetle types" look like and what would it have to do with proving or disproving the fact that pine beetles are squeezing out 2 generations where they used to make 1?

Nroush
Nroush

Good article about the pine beetle devestation, however the title is misleading. The subtitle additionally says why the forests ate burning up, like there is a correlation between the beetle and all of the current fires. There is only a few sentences that talk about the fires and it never mentions a correlation between the two problems. False advertisement!

Phd
Phd

The article is an example of lacking journalism filled with a lack of citations and filled with conjecture. Worse, the article is stale information. The beetle kill is common knowledge and the simple method of "They set up lures loaded with pheromones to invite beetles to establish broods in those trees." Then stating warm winter sampling represents the first peer-reviewed report of the insect achieving two generations in a single summer. Show this result without luring beetles with pheromones. Then try the same experiment with pine bettles during a cold winter. And finally try the experiment with other beetle types.

Edmund
Edmund

Yea, you're right. He should have written it as "The top ten things you didn't know about pine beetles!" Or maybe 5 in your case.

Ranger
Ranger

Single season multi generations during an upswing in warm winters gets you excited? Read closely, and I see your comment about jerking off - that polishes your stance. Plain, simple, concise and without argument - it’s lack of forest diversity. Now you can once again start your multi seasonal pseudo physical and biased masturbation and please stop writing comments where you have no expertise or degree. Grower, thank you.

 
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