About Wildfires

What is a Wildfire?

A wildfire is an uncontrolled fire originating in rural areas that spreads quickly through vegetation and any available fuel.  Their behavior can vary drastically through conditions such as dry vegetation, humidity, topography, and wind.

On August 16th, 2020, a thunderstorm composed largely of dry lightning ignited 24 small fires in San Mateo and Santa Cruz counties.  These fires, combined with intense wind conditions, formed the CZU Lightning Complex fires.  At maximum, the CZU fires spread as far South as Bonny Doon, only a few miles away from the UC Santa Cruz Main Campus.  On August 20th, the decision was made to fully evacuate the campus.  After a few days of careful monitoring alongside California Department of Forestry and Prevention (CalFire), the risk to campus was deemed low and people were brought back to campus in phases beginning August 25th.  

On August 18th, 2020, that same thunderstorm ignited what would become the SCU Lightning Complex fires.  Although much further away from the main campus, the fires did affect the UC-managed Lick Observatory in the mountains near San Jose, CA.

Also on August 18th, 2020, a suspected arsonist ignited the Dolan Fire, affecting UC Santa Cruz’s Big Creek Reserve in Monterey County.  

In combination, these three fires accounted for over 600,000 acres burned and thousands of buildings damaged or destroyed.  They represent only a portion of the increasing proliferation of wildfires in the Western United States.  The CZU Lightning Complex fires marked the first time in UC Santa Cruz history that the campus was evacuated.  

Santa Cruz County is no stranger to wildfires, but they have certainly increased in intensity and spread in recent years.  Below is a table that illustrates wildfires affecting the county since 1954.  Prior to the 1950s, historical records of wildfires become sparse for Santa Cruz County.  

The Wildfire Lifecycle

Wildfires follow a basic life cycle that includes ignition, growth, management, and extinguishment.  Each stage is described below.  It is important to note that the recipe for a fire is relatively simple, all that is needed is fuel, oxygen, and heat.  Every other variable or condition can make a wildfire more likely or more dangerous, but the wildfire itself follows a simple structure.

1. Ignition - Since oxygen is present all around us, the primary needs for a wildfire are fuel and heat.  This can include embers from burning debris, cigarette butts, unattended campfires, arson, and lightning strikes.  If dry vegetation surrounds this ignition source, it can quickly catch fire and move to the next stage.
2. Growth - The chief component of a wildfire’s danger is its growth.  A wildfire will quickly consume dry vegetation and spread to anything nearby that will burn.  This could be more dead vegetation, trees, debris, or flammable structures like homes. A wildfire’s growth is one of the most challenging aspects to predict, monitor, and combat.
3. Management - This refers to everything that firefighters do to combat the spread of the wildfire.  It includes using water and flame retardant to make it harder for the fire to find oxygen and fuel to continue growth.  It also includes using resources like fire breaks and control lines to create areas where there is no fuel for the wildfire to expand to.  
4. Extinguishment - A wildfire is considered fully contained when the entire perimeter of the fire is surrounded by a control line where the fire cannot spread to nearby fuel.  At the same time, any unburnt fuel within the control line is removed and remaining flames are subdued until there are no detected flames within the control lines.  

Wildland Fires and Prescribed Burns

To put it succinctly, all wildfires are wildland fires but not all wildland fires are wildfires.  ‘Wildland fires’ is a broader term that includes purposeful, controlled fires such as prescribed burns.  When fire officials can safely control environmental variables and minimize the danger of a fire getting out of control, they will initiate a prescribed burn to accomplish one or more of the following goals:

• Creating diverse habitats for plants and animals.
• Assist in the recovery of endangered species.
• Vegetation management and wildfire prevention.

Forests have evolved to include wildfires as a part of their lifecycle.  Numerous species can only thrive when a fire occurs by clearing out dead organic matter and increasing soil fertility.  Additionally, the controlled nature of prescribed burns allows for the risk of larger fires to be minimized by restricting their fuels.  

Further Reading:

• National Geographic, The Ecological Benefits of Fire
• National Park Service, What is a Prescribed Fire

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