Burning Issues

Clearcutting in western forests has depleted the stock of old-growth and mature trees and altered the distribution of species. Fire suppression has allowed dense buildups of downed trees and woody undergrowth on forest floors, and eliminated the natural process by which young trees are thinned out and the survivors made healthy.

Enter the new fires of today. Kaboom.

The fires of recent years, like the forests, bear little resemblance to their predecessors of 100 years ago. A wildfire in New Mexico this summer burned 17,000 acres in one day. Several fires in Montana have consumed 9 to 13,000 acres or more over the same period. The catastrophic Foothills fire of 1992 in Idaho traveled 18 miles in 10 hours and decimated 250,000 acres—including the oldest standing ponderosa pine in the state, a tree that had withstood centuries of more natural fires.

These are not low- to moderate-intensity ground fires. Fires today are far more likely to reach catastrophic levels, generating temperatures that may reach 2,000 degrees Fahrenheit—enough heat to melt glass or a steel tool.

When the Fires Are Out
In the wake of such blazes, little or nothing survives. Mature trees are turned to ash. Ecological processes suffer setbacks that may not be corrected for hundreds of years. The Foothills fire in Idaho burned so hot that lichens on rocks were incinerated and the soil itself altered. Nothing grew in some areas for two years; the soils here took on a strange aspect called “hydrophobia,” in which rainfall or snow could not penetrate a waxy layer that developed about two inches below the surface. Hydrophobia isn't well understood, though it is linked to the extreme heat of today's fires. A powerful thunderstorm later dumped a large amount of rain on this dead zone, and in a period of hours an astonishing 3.5 inches of topsoil washed away—soil that had taken 1,600 years to create. The tidal wave of soil traveled downslope and buried a stream, wiping out much of the aquatic life.