Good night, sweet trees

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?

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