The Sierra Nevada, with their rugged terrain and majestic forests create wonderful views and peaceful living environment. But with the characteristic dry summers they also create extremely severe wildfire conditions. The native trees and shrubs found in the forest are fire-adapted plants. Fire played a major role in their development and in the evolution of our forest ecosystems. Prior to the 1900’s, fires set by lightning and by California’s indigenous people periodically burned the forest. This practice was continued through the early 1900’s by livestock producers. Low intensity fires were useful in clearing out small trees, shrubs and dead or dying plants. Frequently this gave the forests a “park-like” appearance, with widely spaced large trees, a scattering of brush and some large expanses of grassy areas.
In the early 1900’s came a policy of preventing fires and quickly suppressing those that started. Over the decades this has resulted in an extreme buildup of fuel in the forest and the occurrence of more devastating wildfires. Trees now grow closer together with intertwined canopies and the density of shrubs is much greater. This increase in vegetation, or fuel, makes it extremely difficult, and in some situations impossible, to control forest fires once they start. The intermingling of tree canopies provides a highway for fire to spread through the forest.
Agencies with responsibilities for managing wildland and forest resource and for fire management, such as the US Forest Service and the California Department of Forestry and Fire Protection realize that these forests must be managed to reduce fuel loads, which reduces the potential for catastrophic wildfires. Experience and research have shown that strategically removing trees to create spaces between the crowns of remaining trees reduces the amount of fuel present and is an effective means for reducing the wildfire threat. Thinning also reduces the moisture stress on the remaining trees making them less likely to carry a fire. Also, removal of some of the dead or dying tress reduces a highly flammable fuel from the forest. While these trees will eventually fall and lay on the forest floor, where they can provide some wildlife habitat, they can intermingle with brush creating a significant wildfire hazard. Brush control is also essential in certain areas for reducing the wildfire potential. Large patches of brush, or brush directly below the canopy of trees, can lead to catastrophic wildfire.
Whether in the forest or around homes, fuel reduction is often needed to protect natural and personal resources, including homes. The goal is to eliminate unnaturally large amounts of fuel and the “fuel ladder.” Selective removal of shrubs will reduce the total amount of fuel present, thus reducing the frequency and intensity of wildfires. Vegetation management of this sort can also eliminate the “fuel ladder,” where grass grows beneath brush, which grows beneath trees providing fire with an easy route from the ground to tree canopies.