I look out the car window from the back seat, the car is driving down Highway 15 from Las Vegas to Los Angeles at 80 miles per hour. 

“Mom, what are those spiky plants called?”
“They are Joshua Trees.” 
There is no way that these spiky and dead-looking plants can be called trees. They are definitely not trees because they don’t even have the tree crown: they are completely bare, just dry, crippled, and dark sticks standing throughout the desert landscape. Little did I know, the trees have gone through wildfires. The flame dulls their luscious crown, stains their skin, and depletes them of their life while the trees bravely endure the torture. 

Fire in the Desert
Unlike forest ecosystems, wildfire is not a natural part of the desert ecosystem. 

“Prior to 60 or 70 years ago, the deserts were not filled with invasive grasses because invasive grasses couldn’t live on the desert soils, there weren’t enough nutrients for them. So, if lightning struck a Joshua tree, it might burn that tree and a few feet around it, but there wouldn’t be enough fuel on the ground to carry the fire to the next plant. So, the fire would be limited to at most a couple of acres, rather than hundreds or thousands of acres, which happens now,” said Dr. Barrows, an environmental scientist and associate professor at the University of California, Riverside.

Joshua Tree National Park Fire 04.2022
In April of 2022, the Elk Fire burned through 431 acres of Mojave Desert landscape. According to the San Bernardino County Sheriff, this fire was sparked by two teenage campers on the southwest side of Yucca Vally in Joshua Tree National Park. 

The vegetation in Joshua Tree National Park was sparsely located in the past. This loose distribution of burnable fuel heavily limited the degree of wildfires in the park before. 

Now, environmental scientists identified a correlation between an increase in invasive plant species in the park with the larger scales of the recent wildfires in the Mojave Desert. 

A few different factors contribute to the increase in invasive grasses. One such contributor is the increased concentration of nutrients in the soil. One hypothesis is that as the smog from the Los Angeles air basin travels into the desert, it carries nitrogen with it. Nitrogen is an essential ingredient in commercial fertilizers used in farming. Thus, the increased deposition of nitrogen on the desert soil allowed a denser grass population to grow. 

Another factor to make the situation even worse is the prolonged periods of drought experienced in the Mojave Desert in comparison to years before. Now, the little spark from lightning or human activities can turn into a devastating desert wildfire with all the dry biomass to fuel its growth into something unimaginable. 

Dome Fire 08.2020
Another even more devastating fire in recent years is the dome fire — a 43,273-acre wildfire that burned through the Joshua Tree woodland of Cima Dome.  

The Dome Fire created a vast Joshua tree graveyard, burning everything that it touched. It is estimated that as many as 1.3 million Joshua trees were killed in the fire together with cactuses, bushes, shrubs, and grasses. According to the National Park Service, 25% of the contiguous Joshua tree forest was burned. 

On the afternoon of Saturday, August 15, the Dome Fire’s smoke plume was first reported. It was started by a lightning strike in the wilderness areas. The fire responders did not hesitate to rush to the scene. They quickly discovered that the fire had great potential and ordered aircraft for additional aid. However, these requests were denied due to the volume of wildfires burning in California at the time. 

On Sunday, August 16, the fire created its own weather. Firenadoes were created from downward fire whirls created by a collapsed convection column. Essentially, the fire in one area rose so high that the atmosphere stopped its vertical growth. The fire has nowhere to go, so it collapsed creating winds intertwined with fire, spreading the fire at an extreme rate to the peripheral areas. 

The resilient prosperities of desert plants will allow them to grow back quickly after the fire from their surviving root reserves. Most of these plants, however, are invasive grasses — such as red brome and cheatgrass — which will grow thickly low to the ground. This creates a fire-grass cycle, where the invasive grass will add continuous and more concentrated fuels for the wildfires by filling the space between shrubs. 

As for animals, lead wildlife biologists from National Park Service estimated no more than 20% fire-related mortality for snakes, lizards, squirrels, rabbits, and other small animals in the burn area. 

The desert tortoise is protected as a threatened species under the Endangered Species Act. The burn area is listed as a desert tortoise's critical habitat. Wildlife biologist estimates that tortoise mortality was perhaps a dozen individual. 

While this area is home to a large grove of Joshua Trees, other key desert plants also experienced the fire. The wildfire project at the University of Nevada, Las Vegas strives to understand the relation of Sagebrush with desert wildfires and the fire’s subsequent consequences on the plant. 

Sagebrush in Fire
Mountain big sagebrush (Artemisia tridentata subsp. vaseyana)lives primarily in thirteen western states, including the Great Basin area (bordered by the Mojave Desert). The leaves have a silvery blue color and produce a distinctive smell that helps them repel plant-eating animals. 

Sagebrush can easily be caught on fire when the surrounding grasses are dry. Fires allow sagebrush to dominate the landscape by effectively eliminating seeds from other major plant species such as juniper trees. Although fire is a natural part of the Sagebrush landscape, scientists are still trying to figure out the fire cycle for each sagebrush species. This lack of understanding made it hard to do conservation work for sagebrush in the desert. 

After the fire, while other surrounding plants can resprout from protected roots, sagebrush does not have a similar privilege. They easily die in fires, fueling the flames to reach over 30 feet high. It will most likely take more than a few years for sagebrush to dominate the landscape again.

Sagebrush areas host a variety of animal life including sage grouse and pronghorn. If sagebrush is lost, the area will no longer support these animals that depend on it for food and shelter. 

Surprisingly, prescribed fires are currently used to build fuel breaks and to keep a resilient balance of sagebrush ages on the landscape. Even though “the wildfires can release considerable amounts of carbon to the atmosphere and then can be carbon sources, rather than sinks, for decades after fires,” according to Dr. Abella, associate professor of restoration ecology in the Life Science Department at the University of Nevada, Las Vegas. 

Comparison of Fuel Potential: Sagebrush vs. Grasses 
Wherever sagebrush is growing, there will always be grasses growing in the gap between each sagebrush plant. So, if a fire was started, how much does sagebrush contribute to the fire and how much do grasses aid the process? There were two factors that are studied by Dr. James K. Brown from the United States Department of Agriculture, the rate of spread and the fire line intensity contribution. 

According to his research, if the sagebrush coverage is low, the rate of spread of the fire is almost totally dependent on the rate of spread of grass. However, if the coverage of sagebrush increases to 30 or 40 percent, the rate of spread of the fire is noticeably increased, especially if taller plants are the majority. 

Figure 2 — Rate of spread at 13km/h midflame-height wind-speed and grass and forb loadings of 170g/m², 100g/m², and 34 g/m². Grass and forbs are 57 percent alive and sagebrush foliage is entirely alive. 
Fireline intensity is the amount of energy released from a cross-section of unit width through the propagation portion of a fire front over a specified unit of time. Sagebrush contributes more to the intensity of the fire line in comparison to grasses as listed below. 

Figure 4.-Fireline intensity at 13-km/h (8-mi/h) midflame-height windspeed and 100 g/m² (900 lb/acre) of grass and forbs. Grass and forbs are 57 percent alive and sagebrush entirely alive.
As you can see, as the sagebrush coverage increases to more than 10 percent and the sagebrush height approach 120 centimeters, the fire line intensity approach 500 kw/m. This is a limit to where people are unable to work at the fire edges. In this case, direct attack with hand crews may become difficult. Just to help you better contextualize the fire line intensity shown on the graph above, here is a table estimating the correlation between the intensity of the fire line with the fire situation. 

Some confounding variables in the experiment include the fuel moisture content, wind, slope, and the amount of dead stem wood. Out of these variables, the fuel moisture content influences fire line intensity most profoundly. You can observe the effect of moisture content in sagebrush and grass on fire line intensity by comparing figure 4 with figure 5 below (assuming dead grass and sagebrush have lower fuel moisture content than 57 percent alive vegetations under the same circumstances). 

Figure 5.- Fireline intensity at 13-km/h (8-mi/h) midflame-height windspeed and 100 g/m² (900 lbs/acre) of grass and forbs. Grass and forbs are entirely dead and sagebrush foliage is one-third dead.
From the experiment, we can rightfully conclude that the sagebrush and the grass both contribute to the development of wildfires in different ways. Grass contributes more to the rate of spread of the fire while sagebrush contributes more to the fire line intensity. 

After the Fire
It is not hard to conclude that wildfires, which are not supposed to happen frequently in the desert, cause tremendous harm that can be observed in the burned landscape after the fire. 

“Desert tortoises and other wildlife can be negatively impacted by desert wildfires because of protective shrub cover (providing shade and other habitat values), and in some cases, food plants can be killed by wildfires and recover slowly. Humans can also be directly impacted by having infrastructure threats, air quality deterioration, soil erosion, dust generation, watershed contamination, and recreational values compromised for a long time period,” said Dr. Abella. 

Sage Grouse Habitat Destruction
Washington state is a major habitat for sagebrush and sage grouses who depend on the brush for food and shelter. As of early 2020, there are fewer than 1,000 sage grouse left in Washington State. In August 2020, a wildfire in Washington state burned through 413,000 acres of sagebrush landscape, destroying everything that stood in its path. 

Dr. Schroeder, who has studied sage grouse under the Washinton Department of Fish and Wildlife since 1981, estimated that more than half of the remaining population of sage grouse in Washington state, about 500 birds, may have been lost in the fire. While he used to walk up the Mary Jane Hill to count the number of sage grouse in the sage grouse lek (or mating ground) just below, now he can only observe the scorched earth for miles in every direction. 

Dr. Schroeder then points to every compass direction. “If it was just this, but it isn’t just this. It’s like you go over to that hill and it looks the same over there. It looks the same.” His voice breaks and trails off. “There’s no way.” 

Before the fire, Dr. Schroeder has been visiting the lek to do population counts for decades. He observed a significant decrease in the sage grouse population. The population estimates of sage grouse in 2020 determined an average decrease of 44 percent across 12 western states and provinces over the last three years (2017–2020). 

The Martin Fire of 2018, which was then the largest in Nevada State history, burned more than 400,000 acres and destroyed 35 known sage grouse leks. 

Not just the wildfires, oil and gas extraction, development projects, habitat loss, invasive species, and overgrazing are all contributing to the decline in sage grouse number in the past few years. 

With bigger and more prevalent wildfire encounters in the western United States, the sage grouse and other unique animal populations will continue to decrease in the coming years without any interventions. 

Sagebrush Recovery
“The recovery of big sagebrush habitat is one of the largest, if not the largest, ecosystem restoration challenges in the U.S. right now. Hundreds of thousands of acres burn each year, and millions of dollars are invested in trying to restore big sagebrush in these areas,” said USGS scientist Robert Shriver. There are more than 300 species of conservation concern that rely on the big sagebrush ecosystem. 

The USGS scientists studied 531 burned sites in the Great Basin. These sites were reseeded with big sagebrush by the Bureau of Land Management after the fire. They were able to reconstruct the rates of survival, growth, and reproduction of big sagebrush at each of the 531 sites since they were seeded. 

Scientists have discovered that the newly seeded areas have a relatively low possibility of recovery due to the fragile properties and the slower reproduction of the small, young sagebrush plants. 

Sagebrush has a unique biology that hinders recovery. Smaller plants (6 inches or shorter) had only an 8 percent chance of surviving while larger plants (greater than 30 inches tall) had nearly a 100 percent chance of surviving from year to year. The larger plants are also much more reproductively successful than the smaller plants. 

Elevation also plays a role in sagebrush recovery. High elevation often correlates with cooler and more humid conditions. Under such conditions restoring the sagebrush population through seeding is often successful before plants can grow faster. However, at warmer and drier lower elevation sites, it might be more effectively to plant nursery-raised seedlings to increase the reproductive success of the plants on the burn sites. 

What can you do to help?
Wildfires can be hard to imagine in urban cities. However, they are just around the corner. Some of the biggest wildfires might have happened within just 5 hours of driving distance from the urban center you currently live in. What can you do to help prevent wildfires and conserve the desert landscape?

1. Reduce Emission
To reduce nitrogen deposition in desert soils, reducing emissions from passenger cars can make a difference. Although the amount of nitrogen deposited in desert soil has decreased in recent years, the area where it is deposited has increased due to continued urban developments. 

Heavy-duty diesel trucks account for more than 50 percent of nitrogen oxide emissions from mobile sources in the United States. With the technology of electric trucks in the coming years, nitrogen deposition will decrease substantially in the desert. 

2. Avoid Introducing Weed Seeds
As mentioned before, invasive grasses account for the ability of wildfires to grow to an unpreceded scale. Hikers, equestrians, and drivers on backcountry roads often carry weed seeds into the landscape without even noticing it. 

Next time, before you started hiking or driving, check to make sure that your shoes and vehicles are free of mud and plant debris that could carry invasive plant seeds. Horse-riders should especially make sure to feed their horses weed-free seed in the days leading up to and during the visit. Horse dropping could spread invasive seeds to areas miles from any roads which will make it difficult to monitor weed outbreaks. 

3. Careful Not to Start Any Fires
Though most wildfires are started by lightning, there are occasions where human-related activities caused the start of a wildfire (such as the Joshua Tree National Park fire described previously). 

Please only make fires in the pre-existing fire rings, clear some defensible space, have lots of water on hand, immediately drown fires when finished, and do not have a fire at all if it is windy. 

4. Become a Conservationist Yourself!
There are nurseries where Joshua tree and sagebrush seedlings are being grown so that the national park services can re-plant portions of the burned areas every year. There are volunteering opportunities at the Joshua tree nursery at Lake Mead National Recreation Area and more.

If you are interested in joining the cause to rebuild the desert landscape, please click here to contact national park services.