What Causes Wildfires In The West?

Wildfires are now more frequent and more intense in sagebrush country, largely due to the invasion of non-native annual grasses. Photo: Winnemucca BLM

April 23, 2018

Wildfires are now more frequent and more intense in sagebrush country, largely due to the invasion of non-native annual grasses. Photo: Winnemucca BLM

ASK AN EXPERT: Darcy McDaniel, Zone Fire Planner in Nevada, Bureau of Land Management

What causes wildfires in the West?

Western wildfires are started by either human or natural ignition sources. Lightning is the most common cause of naturally ignited fires.

For a quick comparison, in 2017 the Great Basin Coordination Center recorded 1,988 human-caused fires that burned 788,769 acres, and 1,139 lightning-caused fires that consumed 1,315,019 acres.

Though it’s hard to predict where lightening will start wildfires, we know that human-ignited fires occur most often along highways and interstates—especially in Central Nevada where I work. This knowledge helps us strategically plan projects that reduce wildfire susceptibility along transportation corridors, and target fire prevention and mitigation measures.

Have fire patterns changed over time in sagebrush country?

Definitely. We’re seeing larger and more frequent wildfires, namely due to the rise of invasive annual grasses like cheatgrass and medusahead-rye. These non-native grasses thrive on the disturbance created by a wildfire, outcompeting native vegetation and causing a vicious grass-fire cycle.

This cycle has resulted in dramatically altered fire regimes — especially in the Great Basin states. Before the spread of invasive annual grasses, you might see wildfire in the sagebrush-steppe every 60-100 years.

Unfortunately, we’re now regularly observing a 3- to 5-year fire cycle in cheatgrass-dominated areas.

Photo: Winnemucca BLM

Cheatgrass and other non-native grasses have dramatically altered historic fire patterns in the American West, outcompeting native plants that keep sagebrush range productive. Photo: Winnemucca BLM

How do we assess the risk of wildfires?

Not every ignition turns into a problematic wildfire. How the fire behaves depends on a number of factors, including the amount of available fuels in the area.

In preparatory planning for tackling wildfires, we often assess and monitor the area’s vegetation characteristics — fuel loads, composition, moisture content, and the extent of vegetation monoculture. This helps us predict fire behavior and also anticipate the progression of the fire.

Can we lower risks before fires occur?

Yes! Land managers like the BLM have a suite of treatment options designed to minimize and arrest the spread of wildfires.

Many of our fuels reduction projects are prioritized based on the proximity to resource values at risk, including infrastructure and critical habitat. We also prioritize projects along highways where ignition rates are high. In more remote areas, we may develop roadside fuel breaks to improve access for fire suppression resources while reducing the potential for fire occurrence and limiting fire spread.

Usually, we combine several treatments on a landscape and stagger them over time to provide the best results. Treatments can include:

Photo: Winnemucca BLM

Applying herbicides that target certain problem species, such as invasive annuals like cheatgrass.

– Disking or plowing techniques that expose mineral soil, which won’t burn and therefore creates a fuel break.

– Mowing vegetation to alter its height (just like cutting your lawn at home), which moderates fire behavior, intensity and flame length.

– Prescribed burning to lower the amount of available fuel.

– Seeding or hand-planting native vegetation to promote wildfire resistance and ecosystem resilience.

– Planting green strips or vegetation fuel breaks made of fire-resilient plants.


Do wildfires affect sage grouse and other wildlife?

Unfortunately, yes.

Wildfires with high burn severity often degrade habitat for sagebrush-dependent wildlife.

Animals that survive will need to migrate to another area in search of food and shelter. Since it often takes several years for the flora to recover post-fire, it can take even longer for birds and animals to come back — if they come back at all.

How do we minimize impacts to birds and animals?

We analyze a variety of data to target fuels treatment efforts in important wildlife habitat. For instance, we can overlay GIS data showing core sage grouse habitat to help prioritize treatments.

Since sage grouse require such expansive habitat, it’s really important to collaborate and communicate with neighboring districts and states when planning fuels treatments. The Tri-State Fuels Treatment program is a great example of a partnership between BLM agencies in Idaho, Oregon and Nevada that extends the effectiveness of our work across jurisdictions.

The BLM and our partners also work cooperatively on post-fire revegetation projects to create green strips. We focus on seeding or planting fire resilient plant species where cheatgrass is most concentrated to try to disrupt the grass-fire cycle in these areas.

By altering vegetation dynamics, we increase the landscape’s resistance to invasive species like cheatgrass and resilience to disturbance such as wildfire. This provides added benefits for wildlife, too.


What gives you hope when tackling wildfires?

I’ve been working in wildland firefighting since 2001 and can attest to seeing larger and more destructive wildfires over that time. But it’s always promising to go back to an area a few years after a fire incident and see native grasses, forbs, and shrubs starting to grow back.

This regeneration is a testament to landscape resiliency.

One positive thing that has really stood out to me is how well we’re integrating geospatial technology in fire planning. We can now track and share information, often instantaneously, with other individuals and agencies. These technological tools are essential for collaborating with other agencies, communities, and private landowners.


Darcy McDaniel is a zone fire planner with BLM in Nevada.

Darcy McDaniel has on-the-ground experience fighting wildfires, and is now a zone fire planner with BLM in Nevada.

Tell us about your experience with wildfires.

Prior to fire planning, I worked for the U.S. Forest Service for over 11 years as a hotshot firefighter. I have worked on six different crews and four regions traveling the United States on fire assignments.

I’ve been with the BLM for almost two years here in Nevada, where I provide fire planning and decision support. This includes GIS support for fire and fuels, technical assistance with mobile applications, and helping with fuels management projects including NEPA.

Since I wanted to diversify my professional experience, I recently completed a Master of Natural Resources degree with a specialization in Fire Ecology and Management from the University of Idaho last December.

What do you like to do in your free time?

Now that I’m not doing homework every night after work, I’ve been able to resume my favorite past-times again — hiking and trail running. I love being outdoors!

See a map of ecosystem resistance & resilience >

Learn more about the grass-fire cycle >

Read more Ask An Expert posts >


The Sage Grouse Initiative is a partnership-based, science-driven effort that uses voluntary incentives to proactively conserve America’s western rangelands, wildlife, and rural way of life. This initiative is part of Working Lands For Wildlife, which is led by USDA’s Natural Resources Conservation Service.