News ID: 254725
Published: 0512 GMT June 23, 2019

Wildfire can affect the environment in more ways than you might expect

Wildfire can affect the environment in more ways than you might expect

A fire needs three things to start and survive — oxygen, heat and fuel.

“Any organic materials, living or dead, in the ground or on the ground, or in the air like tree branches that will ignite and burn,” said Eric Chapman, the Bureau of Land Management fuel assistant fire management officer in Casper in Wyoming, the US, wrote.

Once a fire is burning, there are a number of factors that affect the damage, or good, the fire will do.


Topography and soil


Topography, the formation of the land, can influence how a fire will travel. The topography and fuels that come with a mountain landscape will influence a wildfire more than an open location, which leaves a fire more exposed to external climate factors such as wind, Chapman said.

Once a fire ignites, it can have catastrophic effects to the soil. An extremely hot fire that burns the ground can create a surface called the hydrophobic layer, said Dan Mattke, an area resource soil scientist for the Natural Resource Conservation Service in Riverton.

The hydrophobic layer is made up of a waxy material created from burned organic material that keeps water from being absorbed into the soil. This layer seeps under the top layer of soil as a gas then solidifies, Mattke said.

The repelled water will run off into nearby streams and creeks, causing water levels to rise. Erosion displaces fertile topsoil, carrying sediment that may clog streams and lower the water quality.

Water turbidity also rises when water is repelled from the hydrophobic layer. Turbidity is the process of sediment being in stream and creek water, creating a haze and lowering the water quality, said Ryan DeSantis, the forest health program manager for the Wyoming State Forestry Division.

If the hydrophobic layer isn’t properly dealt with, it can affect melting snow. Mattke said the burned black top will “absorb more heat, melting the snow faster.”

Tilling soil is the best way to diminish the hydrophobic layer, DeSantis explained. Breaking the soil apart brings the soil under the hydrophobic layer up and can help moisture be absorbed and help seeds to take root.

To reduce erosion, there are multiple options, such as water bars — channels created with soil and bedded logs to funnel water away from a burned area, said George Soehn, resource adviser for the BLM.

Reseeding, the process of planting native seeds to keep the soil in place, is another option. Dead trees can also be chopped down and placed at a contour perpendicular with a hill slope to act as water breaks and soil traps, Soehn explained.

If organic matter is still present when a burn happens, instead of the hydrophobic layer being created, the soil itself is damaged.

“If you have a fire that can get hot enough, you’re pretty much burning off organic matter and you’re basically sterilizing the soil,” DeSantis said.

Sterilized soil can reduce the chance of bigger vegetation like trees growing. The 2012 fire near Laramie Peak burned an estimated 98,115 acres before being contained. The area still looks pretty black with some regeneration like grasses, DeSantis said.




Precipitation can have a major impact on a fire’s severity.

More precipitation can lead to more vegetation during the growth season. That creates more fuel for a fire, according to Brett McDonald, a US National Weather Service science and operations officer.

Once a fire has started, rain for a long duration of time is preferable to a large amount of rain falling quickly. The longer rain falls, vegetation and the ability to burn is affected.

A lot of precipitation over a short period of time causes run-off and doesn’t have long-term effects on vegetation, said Flint Cheney, planning section chief of the Rocky Mountain Type 1 Incident Management Team.




Fires aren’t all bad, though. Fire is a healthy and natural change, said Soehn, the BLM resource adviser. The negative connotation is only applied when humans enter the situation.

Different species of trees, like the lodgepole pine are fire dependent. They require a stand-replacing fire — a fire big enough and intense enough to kill a large area of the trees. These fires help the tree reproduce, as it has two kinds of cones — ordinary cones that release seeds seasonally and serotinous cones that release seeds with extreme heat, like fire, or intense sunlight, DeSantis said.

Soehn explained the only reason for humans to step in is to eliminate nonnative invasive species of plants like cheatgrass or knapweeds. Herbicide chemicals are used to kill invasive species and reduce the regrowth.

The reseeding of native plants helps jump-start the area. Forests in a healthy condition before a fire can recover by themselves in a timely manner, even as soon as the following spring, Soehn said.

While wildfires can do a large amount of harm to human life, they can certainly help the environment.

“It’s probably best to let nature do what it’s been doing for thousands of years,” Soehn said.


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