Fire in nature plays an important role in ecosystems, helping to maintain biodiversity and nutrient cycling. However, human activities cause wildfires, which devastate lives and property, exacerbate climate change, and are often a symptom of over-crowded forests.
A wildfire needs two things to start and spread – an ignition source, and fuel. “Fuel” is anything that can burn, including grass, trees, mounds of twigs and pine needles, and houses and other structures. Fuel availability and aridity determine how easily a fire ignites, burns, and spreads. Fuel aridity is related to weather, especially temperature and humidity. High temperatures, droughts, and lower humidity dries out fuel sources making them more easily combustible. Topographical features, such as slope, elevation, and aspect, also influence how quickly and how far a fire progresses. When fire ignites at the bottom of a steep hill, hot air rises and preheats fuels further uphill, enabling them to burn more easily.
The combination of these factors contributes to wildfires that are larger, more intense, and more widespread than they used to be. These conditions are a result of global climate changes that are increasing the frequency and intensity of wildfires, with corresponding impacts on people, wildlife, and ecosystems.
To reduce the risk of wildfires, we need to create more resilient landscapes. CDFW works with partners to address new challenges from extreme wildfires and to create landscapes that can support natural wildfires while promoting California ecosystems and biodiversity. One key to this effort is creating defensible space, a land management practice that involves clearing or modifying vegetation near homes and other buildings in the wildland-urban interface. Defensible space reduces fuel continuity by removing brush, piles of wood or other combustible debris, and flammable decorative arrangements from around structures. It also includes implementing forest management practices such as pruning and thinning that can remove closely-spaced branches and twigs, which act as ladder fuels and allow fire to spread quickly from the ground up into the canopy.