Sierra Nevada Fire Ecosystem

The biggest resource change from the past is both the gravest threat, and the hardest to see. That is fire, and how it has been managed, or mismanaged, over the past 150 years.

Fire, and its frequent return, is a natural part of the Sierra foothill and mountain ecosystems. The Nisenan thought so highly of the effects of fire they shortened the fire return cycle to every two to three years. But since the Gold Rush, few have allowed fire to burn naturally in the forests. And the logging, fuel wood cutting, grazing and clearing for various reasons have left an unnatural legacy of vegetation. Fire suppression and putting out forest fires has even been a priority.

The result is a forest overgrown to hazardous degrees. The forest canopy is thick with trees touching shoulder-to-shoulder. The understory of brush and built-up dead materials is excessive, making any small fire quickly flare into a raging inferno. Our introduced plant species contribute to the problem — tall European annual grasses like rye, oats, and foxtail have taken over from the native perennial bunch grasses, increasing summer fire dangers. Fuel loaded forests and fire danger at present levels is a condition that has never before existed in the millions of years of Sierra Nevada forest evolution.

This is a nasty dilemma, and arguably, a most serious challenge. Will we ever be able to re-introduce fire into the natural fire ecosystem? Will we have to mimic fire's results by hand to restore our forests to a safe, natural condition? Will we do nothing and wait for an inevitable catastrophic fire? One of the first steps is to train our eyes to see the problem. Then learn small steps that can be taken. (See Colfax Community Watershed and Fire Safe Ecosystem Project for steps you can take.)

Fire Treatment Demonstration



A fire treatment demonstration site was created to show people how to begin to return to more safe, more natural, conditions. At top right is the site before treatment, with young fir trees so thick the forest experts refer to it as "dog hair". This condition will burn extremely hot, and flames will immediately shoot into the canopy of larger trees. The fire will be completely destructive to the forest.

At bottom right is the same spot after what is called "shaded fuel break" treatment. A fire can burn through the area under the trees, as the understory is kept open of shrubs and dense "dog hair". The canopy is not crowded (note shadows), so the fire will not move from tree to tree. This condition, while accomplished by hand and machine, mimics the natural fire ecosystem of the Sierra Nevada. The early settlers told in their journals of running their horses at full gallop under the open forest of giant firs and pines. Such was the condition of the forest before 1849.

Forest Structure

The structure of the forest is very different in these comparative historical photos. The original forest had wider spacing, a mosaic pattern, and more clear understory. The modern forest is even-age, over-crowded, and far more prone to catastrophic fire. (Historic picture from George Gruell's great book, Fire in Sierra Nevada Forests: A Photographic Interpretation of Ecological Change Since 1849.)