Good night, sweet trees

Sudden Aspen Decline is like a Shakespearean tragedy

  • Dead aspen stand near Fairplay, Colorado and Highway 285.

    William R. L. Anderegg
  • Reasearchrer, Alex Nees begins his ascent of an aspen tree to take canopy measurements.

    William R. L. Anderegg
  • Alex Nees in the canopy measuring aspen photosynthesis.

    William R. L. Anderegg
  • Trees afflicted by Sudden Aspen Decline in the San Juan National Forest, Colorado.

    William R. L. Anderegg

June 25, 2009
In the pale predawn light, the branches of the aspens clawed at the sky as if trying to drag any moisture they could from the dry, cold air. The slow call of a mourning dove sounded in the distance as the first sun touched the uppermost branches. It was time to start my measurements. I grew up camping and hunting with my family across southwest Colorado, often in the dappled and dancing shade of aspen trees. Now I had returned to work on my doctoral dissertation. And one of my first research sites was here, in the very aspen stand that I had spent so much time exploring as a kid.

No one's childhood memories of a place survive returning to that place as an adult. Things seem to grow smaller, or dingier, with age, even if they haven't changed in reality.  But here, the trees I remembered so clearly had changed. They were dead, all of them, their once leafy branches bare and skeletal. I had known they would be, of course. I had returned to Colorado after six years to study the mysterious, widespread aspen die-off, but I didn't foresee how visceral, how shocking it would be.

Sudden Aspen Decline, as researchers call it, has hit this part of the Rocky Mountains hard. Nearly 20 percent of the aspen trees have died over a four-year period. Along with several other researchers from Stanford University, I spent the summer camping in the forests I grew up in, trying to figure out why. I did my work with cold detachment, with a jumble of scientific instruments, but I mourned inside.

August 5, 2009
I straightened my tie with trembling hands and glanced out at the crowd assembled at my hometown's Cultural Center. Abruptly, I understood the trepidation that most scientists feel giving public lectures. Worse yet, I had put climate change in the talk's title and, though confident about the science, I was nervous about discussing it here. Cortez is a mid-sized farming town in a rural, deeply conservative county.

I should have served wine beforehand, I thought to myself as I welcomed everyone and put up the first slides. Better yet, whiskey. But I launched into my talk anyway: How many people had noticed the dead aspens on their land or near the road in the mountains? All hands went up. Who remembered the mass death of the pinon pine forests across the Four Corners states several years ago? All hands went up again. Across the Southwest, hundreds of thousands of acres of pinon pine had rapidly succumbed to a beetle in just a few years. Scientists found that the severe 2002 and 2003 droughts lasted no longer than those of the Dust Bowl or in the 1950s, but they differed in one very important respect: They were hotter, most likely due to manmade climate change. Our current scientific picture of the recent half-million-acre aspen die-off paints an incomplete picture, but all lines of evidence to date point towards a similar one-two punch of drought and global warming as the primary cause. When I said this, I expected grumbling, if not a roar of disagreement.

But the protests never came. These people had seen the dead forests all around them. The pinon pine die-off had left huge swaths of the landscape a sickly brownish-red. Then the massive lodgepole pine scourge swept across Colorado's high-altitude forests, and continues to wreak havoc today. Faced with mounting evidence on a very concrete level, the locals have come to understand that Western forests are already in trouble, and climate change is the most likely culprit. This audience asked the same question locals had asked all summer -- What can we do about it?

Restoring Aspen With Wolves
Nicole Rodriguez
Nicole Rodriguez
Mar 02, 2010 01:09 PM
I understand there is a correlation to the aspen growth and come back in Yellowstone with the introduction of wolves. Maybe there is a correlation with the aspen in Colorado and lack of animal predation.[…]20aspen%20with%20wolves.pdf
I don't know enough about the growth cycle of aspen's to understand if the die off is of the natural cycle of old growth dying and possibly no new growth replacing it.

I enjoyed the article.
Aspen and wolves
Mar 04, 2010 10:42 AM
Most likely, it is a combination of no wolves, and climate change.
Silly emotional mush
Kenna Sue Shirley
Kenna Sue Shirley
Mar 04, 2010 04:36 PM
This is a perfect example of why Global Warming theory has taken such a bashing the last few months. Where is the SCIENTIFIC basis for saying that aspens are dying because of a warming climate? "Incomplete pictures" and "lines of evidence which point toward" are simply no basis for any kind of scientific conclusion. And may I point out that we have aspens in Ohio which live in a warmer climate than your Rockey Mountain situation, so I doubt highly that miniscule amounts of warming have decimated their ranks in the Rockies.
Aspens, CO vs. OH
Stephanie Rohdy
Stephanie Rohdy
Mar 05, 2010 10:45 AM
Ecology is about the context of an area as well. There may be aspens in Ohio, but they live in very different environmental conditions then aspens do in Colorado. Elevation plays a critical role on the ability of species to thrive in different areas.
CO vs. OH
Kenna Sue Shirley
Kenna Sue Shirley
Mar 10, 2010 12:24 PM
I think you just said what I said, that there is more going on than climate warming.
Causes of SAD?
Jodi Peterson
Jodi Peterson
Mar 12, 2010 01:53 PM
Posted on behalf of John Dalmas: In 1967, at age 41, I earned a PhD in forest ecology from Colorado State in 1967. For 17 years, beginning in 1960, I was a research ecologist at The Rocky Mtn Forest & Range Expt Station in charge of aspen research and mixed conifer research. Earlier (1956-58) I sold timber, mostly aspen, for the USFS in Wisconsin. Prior to college I worked seasonally logging mostly aspen pulpwood in northern Minnesota and Upper Michigan. And as Dr. John R. Jones, I was the lead author of "Aspen: Ecology and Management in the Western United States," a good source for information on aspen. My boss, Assistant Director Lloyd Hayes, introduced me around as the country's "leading expert on aspen." Maybe I was, but when I left in 1977, there remained a lot I didn't know.

I was saddened to read about the aspen die-off. I don't KNOW the cause, but I'd like to share some speculations with you. Food for thought.

Aspen clones in Colorado and Utah have been defined and mapped that cover in excess of 100 acres. I'm willing to accept that. A clone originates from a single seedling, from buds on the roots. I occasionally saw new aspen seedlings in the west, and when I did, I staked it so I could find it again. It was never there at summer's end. It's been speculated that most aspen clones in Utah and Colorado date back to the Pluvial; we're talking the last ice age. (I haven't seen a climatic reconstruction for the warm wet period period that followed the Two Creeks resurgence.)

It seems very likely that the extensive aspen forests in Colorado and Utah (and Wyoming and New Mexico) are very old clones. On favorable sites in the west, aspen trees (the above ground parts) can live upwards of 200 years, and can grow to heights of over 100 ft., large handsome trees, sometimes still gaining in height. But those are moist and fertile sites, often with an understory of Engelmann spruce and other shade tolerant conifers. I rather suspect that the die-off missed such sites, unless the trees are very old.

On the other hand, aspen stands on the warmest sites were open and scrubby, I suspect from multiple factors: inadequate moisture for example, and livestock. Such stands were commonly disintegrating even then, their roots sending up new shoots which ruminants domestic and wild were eating. I envisioned the degenerating aspens becoming so sparse and weak that the root network starved out and sent up very few suckers, which livestock or deer and elk ate. I thought then they'd be gone in the not distant future.

Historically, stands of large, mature or older aspens (and some not so large) had followed fires that burned through heavy herbaceous growth or coniferous understory. Aspen trees are readily killed bv fire, but the extensive clonal root network survived and suckered profusely. Sometimes recapturing the site promptly, and sometimes over a period of several years. But when the pre-fire aspens were sparse, the new stand filled in more slowly. In any event, fire tended strongly to rejuvenate the clone or clones.

Were it not for human intervention, I feel confident many of the stands of the early 20th century would have burned, and there'd be a lot more dense young stands.

Climatic warming may shift the zone of aspen die-off to higher elevations, but still higher up, I suspect die-off is absent or not as severe. Eventually aspen will die out, high or low, if there is no fire.

Unless clearcutting does the job. In 1995 I drove past extensive new aspen clearcuttings, I believe on the Gunnison NF, on the way to Paonia. (I'd like to have stopped but it wasn't my call.) Those had to have been good stands on good sites, or they wouldn't have been logged, and I expect they suckered prodigiously. If they're not flourishing, then my speculations above are invalid. Give 'em a look.

And keep up your good work.

John Jones AKA John Dalmas
Dying Aspens
Kathleen Ulrich
Kathleen Ulrich
Oct 19, 2010 03:29 PM
The aspen outside of Flagstaff, AZ have been dying off in greater numbers every year for the past several years. The lovely stands are now blackened toothpicks. But also, there are growing groves of dead Ponderosa pines, beginning the minute one gains the high plateau country. Every day the public drives by and seems not to notice. Montana has mountains of dead trees, thanks to the bark beetles. Perhaps we feel the losses are greater than our capacities to prevent the losses. Thanks for the excellent article.
Jim Jones
Jim Jones
Sep 30, 2012 06:01 PM
I can tell you the phenomenon what's killing the aspen trees. It's human-made and it is called: CHEMTRAILS. Do your own research, Google and Youtube "chemtrails" spend days watching videos etc.