Why some plants can withstand wildfires better than others
The devastating Camp fire became a massive blaze that engulfed more than 153,000 acres, killing at least 85 people and destroying nearly 14,000 homes in northern California. The fire is now 100 percent contained, fire officials said on Novem. The New York Times notes that containment doesnt mean the fire has been completely extinguished, just that firefighters have created a line around it.
One of the key components to the development of wildfires across the western United States is the amount of fuels that are readily available to cause fires to spread more rapidly.
In California, the abundant vegetation that has grown following wet winters the past several years has dried out during the spring and summer seasons. This combined with weather factors such as low humidity and strong winds provides optimal conditions for fire development.
While there is no such thing as a fireproof plant, some burn less easily than others and that comes down to a plant's chemical composition.
Plants that are flammable are often that way because of their chemistry, according to Peter Fulé, a professor in Northern Arizona University’s School of Forestry.
A firefighter battles the Holy Fire burning in the Cleveland National Forest along a hillside at Temescal Valley in Corona, Calif., Thursday, Aug. 9, 2018. (AP Photo/Ringo H.W. Chiu)
“They often contain chemicals that have a lot of substances like waxes and resins that burn very easily,” Fulé said.
These waxy substances are useful for plants that grow in drier climates because it helps cover their leaves and protects them from losing water.
The shape of plants also comes into play when it determines how flammable they can become.
“A lot of shrubs in particular are relatively low to the ground and often provide fuel that is kind of nicely spaced so the wind can get in there very well and make it burn quite well,” Fulé said.
On the opposite end, more fire-resistant plants are typically those that lack that waxy characteristic and do not readily ignite from a flame or embers, according to Firefree.org.
Other characteristics of fire-resistant plants, according to Firefree, are:
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Leaves that are moist and supple
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Plants have little dead wood and tend not to accumulate dry, dead material within the plant
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Low sap or resin materials
Larger plants, such as trees, are able to withstand wildfires, but that pertains more to the type of wildfire than the natural material of the tree.
In the U.S., the two main types of wildfires are crown fires and surface fires.
Surface fires spread quickly along the ground and are one of the primary fire regimes that occur in forests.
“Typically, in a surface fire, the larger trees do survive. The fire passes underneath them. It may damage them, but it doesn’t kill all of them,” Fulé said.
Trees have natural adaptations to fire, such as developing a thick bark which insulates the base of the tree to the ground level.
They carry their limbs pretty high up in the tree so the flames pass by but don’t scorch too many of the leaves because the leaves that are actively growing are higher in the tree, according to Fulé.
A crown fire is a more destructive fire, which moves from one crown of the tree to the other. Whole mature trees become giant torches and flames pass from tree to tree in the forest canopy.
“Pretty much every kind of tree dies when the crown of the tree catches on fire,” Fulé said.
A big part of wildfire prevention strategies has involved finding more fire-resistant plants for homeowners to grow around their residences. In some instances, the concept of introduced vegetation has become an issue.
People plant attractive species like eucalyptus, which is native to Australia, and junipers because their easy to take care of. However, they burn very easily, according to Fulé.
Cal Fire provides a list of tips and certain species of plants that are drought tolerant help make landscapes around homes more resistant to blazes.
