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Forest Ecology

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Most of our homes reside on the western slopes of the Sierra Nevada, a Mediterranean climate, fire-evolved ecosystem.  Our climate consists of a rainy season followed by a dry (fire) season with the added bonus of periodic high winds.  Furthermore, our mostly very rich soils provide plants the ability to annually produce vast amounts of biomass (vegetation).  Since our winters stay too wet and cold and our summers remain too hot and dry for rapid fungal decay, this biomass accumulates creating an ever increasing fuel load and fire danger.  Historically, lightning, volcanic eruptions, Native Americans, and early Europeans started fires to keep the ever-increasing fuel load in check.  These repeated mostly low-to-moderate intensity fires maintained cleaner forest floors. All of Nevada County’s native plants and animals evolved under this pattern of periodic fire events.  Repeated fire left forests much more open with fewer trees spaced further apart and periodically consumed brush and small trees thickets. But most importantly, these fires cleansed the forest floor of accumulations of dead biomass (ground fuel). A wildfire cannot maintain itself or its intensity without sufficient continuous ground fuel.  

Today’s forests contain conditions far different than historic forests.  Through fire exclusion policies and poor land management practices, we humans have sent forests down a completely new and destructive evolutionary path.  Some native plants and animals prefer this new direction and thrive; however, most do not.  Our forest ecosystems exist as unhealthy fuel-loaded powder kegs prone to catastrophic fire.  Our forests are weak and sickly due to too many trees growing too closely together. The unnaturally dense brush and small trees provide a fuel ladder for fire to climb into the crowns of trees. The huge amounts of dead vegetation on forest floors provide the perfect medium to perpetuate high intensity fires.  

Humans created most of this fuel-loaded condition and humans must respond appropriately to correct this imbalance. Historically, this relatively new, heavy fuel-loaded vegetation type was never a large component of forests before fire exclusion.  Cleaning by cutting and removing decadent brush, thinning trees and pruning the branches of the remaining trees up eight or ten feet high helps greatly. However, most importantly, removing most of the accumulated dead ground fuel around your home will mimic a periodic fire regime and create a forest setting more similar to what originally existed, a setting where catastrophic wildfire was the rarity not the norm.  

Is a 30-foot clearance around your home adequate protection from a wildfire?  Absolutely not!  In fact, Public Resource Code 4291, the 30-foot clearance rule, was written to protect forestland from individual structure fires, not the other way around.  The law was designed to provide firefighters a 30-foot clearance around homes to help confine structure fires to just the building and not spread to the surrounding forest.  A wildfire racing towards a home presents much greater challenges and risks to firefighters than simply containing a structure fire.  Firefighters need more room to safely maneuver and fight an oncoming wildfire.  

All other wildfire protection and prevention measures mean little if homeowners do not create adequate fuel reduction perimeters. For most homes, a buffer of dramatically reduced burnable vegetation, 100 feet wide, vastly improves the probability that firefighters can save both your life and your home. The better landowners prepare for the inevitable fire event, the safer and more aggressive firefighters can push their protection and suppression efforts.  The faster firefighters gain control, the less loss of life, destruction of property, and damage to existing wildlife habitat.

There are biological realities and biological responsibilities required for all of us to live in and fit into our fire evolved ecosystem.  Ignore these biological realities and responsibilities and you risk becoming a member of a growing number of victims, injured by your own hand.

Written by Robert G. Ingram

Robert Ingram is a licensed professional forester, NCRCD board member, and has fought wildfires and conducted prescribed burns in Nevada County since 1969.

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