Last spring and fall, the Colorado mountains were plagued by wildfires. They raged all over the state, popping up and spreading like—well, like wildfire.
On Oct. 30, one fire in particular started less than half a mile from my family’s house on the outskirts of Boulder, Colo. Early in the morning, a tiny, unnoticed spark leapt from an illegal campfire and quickly proceeded to engulf the hillsides above it.
The fire climbed the hills and gained the ridge—just like I’ve done so many summer afternoons—where it increased in intensity and continued along the high points. In the grand scheme of things, it wasn’t all that big a fire, but under a long plume of smoke stretching across the sky, my father spent the day scattering his carefully cut and stacked firewood far and wide, and removing as much brush as possible from the surrounding land.
That evening, most of the danger averted, we could see embers glowing from a nearby ridgeline—and the next day, my father went out and collected all the firewood again.
About a month later, I ventured past the county warning sign and explored the burned area. In a matter of a few steps, I’d already proceeded into a different, almost stereotypically apocalyptic world. In a way, that’s exactly what it was.
During a particularly high-intensity fire, temperatures on the ground can exceed 900 degrees Celsius (or 1,652 degrees Fahrenheit), and everything that remains after a fire has sustained all 900 of those degrees.
For perspective, that’s 90 times the temperature of boiling water; yellow lava spewing from volcanoes is about 900 degrees C.
With temperatures like these, it’s not surprising that most of the organic matter on the floor (anything that was once alive, basically) instantly turns to carbon dioxide and water vapor. But more than that, even the minerals in the soil don’t come away unscathed.
Elements like nitrogen and phosphorus are volatilized: they spring from the ground into their gas phase and either mix into the atmosphere or re-condense onto other soil particles, forming a kind of waterproof crust. Other elements, like calcium or potassium, are converted to oxides and stay behind in a coating of ash on the ground.
In the midst of a wildfire, the natural world doesn’t adhere to the same rules we think it ought to, and in the aftermath, nothing is quite the same.
Beneath my feet, the ground was a mottled patchwork of black soot with great splotches of rust-colored fire retardant emanating from a single impact area. On the lower hillsides, many of the trees had only been burned on one side; the fire had climbed up the hillward side and then jumped up and over to the next one, leaving the outer branches clinging feebly to still-green pine needles.
At the top of the ridge, though, where the fire had converged upon itself from both sides, this was not the case. Tall pines were nothing more than shrunken, pitch-black monoliths, creaking ominously in the lightest breezes.
In the post-fire world, no colors existed except black, red, and a few shades of brown. The air was thick with an acidic tang that stayed in the back of your throat; not smoke, exactly, more like the smell of burning itself: like carbon liberated unexpectedly from its bonded solid form, like extreme heat and barbecued pine needles.
Most of all, the whole place was silent—except for those dead trees creaking in the wind.
The area seemed still and inert. But in reality, this will be a dynamically changing ecosystem for years, and the aftershocks of a fire take a long time to recede.
Wilderness trails along Missionary Ridge, outside Durango, which burned for a month in 2002, were just beginning to open up again a few years ago. Mudslides and falling trees had made it too dangerous before then. And every time I drive up Boulder Canyon, I’m struck by the still-barren slopes burned by the Black Tiger in 1989, one of the worst wildland fire losses in history.
All those blackened, dead trees will be useless to shade the ground below, and the black ash will greedily absorb every ray from the sun. Stream temperatures throughout the burn zone and below will increase noticeably.
Those volatilized elements on top of the soil will wash downstream with the first rain and dissolve into the water, changing stream chemistry as well as temperature. The weakened soil, stripped of the roots that hold it in place, will be more susceptible to erosion; dry gullies of eroded sediment will appear and landslides will be more common.
And because of all these things—less plant life, less permeable soils, and an eroded, unstable topography—floods will occur more often and with greater magnitude.
Modern fire retardants have a double role as fertilizers, but it will still take a few good years, or longer, for plant life to re-grow. Eventually it will, of course, in the cyclicality of natural processes, which includes fire as a necessary part.
Perhaps we should count ourselves lucky to be alive in a world where we can experience such intensity, and in an epoch where forests, and forest fires, happen at all.
But for now, and for me personally, I’m going to avoid owning mountain land. I’m perfectly happy to experience that intensity from a very safe distance away.
Author’s Note: I learned much of the foregoing in a hydrology class at the University of Colorado, and am indebted particularly to the article, “Effects of Wildfire on Soils and Watershed Processes,” by George G. Ice, Daniel G. Neary, and Paul W. Adams, published in the Journal of Forestry, September 2004.
Vivian Underhill writes the “Boulder Frugalista” column, which runs every Tuesday in the Colorado Daily. She grew up in Boulder, in a family of mountain climbers, and enjoys trail-running, rock climbing and all manner of winter adventures. She’s studying environmental sciences at CU Boulder.