Background

Due to a strong high pressure system to California's west, in mid-August temperatures were abnormally hot statewide, including in the High Desert. Relative humidity was low, and an abnormal lack of moisture from the monsoon that summer meant vegetation was even drier than usual.^[5] This meant that conditions were already conducive to wildfire growth when a plume of moist and unstable air brought north from the decaying Tropical Storm Fausto off the coast of Baja California interacted with the high pressure system in the desert southwest on August 15 and 16. This led to a dry thunderstorm outbreak across California.^[6] Nearly 11,000 cloud-to-ground lightning strikes were recorded, very few accompanied by significant precipitation. The frequent lightning and gusty outflow winds combined with the heat and dry vegetation ignited many quick-spreading fires throughout the state, creating an immediate draw on firefighting resources.

Fire progression

The fire began after one such lightning strike near Deer Spring, an old ranching qanat located on Cima Dome, at approximately 3:22 p.m. PDT on August 15.^[7][3] The Mojave National Preserve fire crew, composed of roughly a dozen personnel, was already at the preserve and arrived on the scene near 5:00 pm, when the blaze was around 70 acres. The fire, driven by erratic winds, was burning into inaccessible wilderness areas, and passing thunderstorms caused the head of the fire to switch directions rapidly, creating extreme and potentially unsafe conditions for firefighting.^[8] The combination of challenging firefighting conditions and the inability to get more firefighting resources meant that the crew was forced to pull back for the night.

The Dome Fire forming a small pyrocumulus cloud on August 15

By 11:00 a.m. the next morning (August 16), the Dome Fire was more than 16,000 acres.^[3] Winds gusted up to 20 miles per hour, and temperatures reached a reported 115 degrees.^[9] This made the fire difficult to stop, and it experienced its largest single day of growth, increasing to more than 40,000 acres. During this time it exhibited active fire behavior, including pyrocumulus clouds and fire whirls. More resources finally arrived on the 16th, a team of smokejumpers from Redding, California, a helitanker, and multiple fixed-wing aircraft.^[5] One of those included the Boeing 747-400 Global Supertanker.^[10] During these first two days, crews also lit backfires—or controlled burns—to stop the Dome Fire's progression to the east, which threatened habitat for the critically endangered desert tortoise.^[7]

A fire whirl forms in the smoke plume of the Dome Fire on August 16

Conditions made the going difficult. In addition to the wind, temperatures remained extremely high; in the Baker area 20 miles to the west of the fire, temperatures reached a high of 117 degrees on August 17.^[11] Another challenging factor was the lack of bulldozers, often used to create a firebreak clear of vegetation so as to stop a fire's spread. The ecologically sensitive nature of the preserve meant much of the firefighting had to be done by hand, with aircraft supporting when available.^[11]

In the afternoon of August 17, the fire's management was transferred to a Type 2 incident management team, which was able to requisition more personnel and resources.^[3] Eight aircraft continued to drop water and fire retardant to halt the fire's spread, which also slowed as it encountered rockier areas with sparser vegetation.^[11][7] During the peak of the suppression and mop-up effort, more than 180 firefighters were assigned to the Dome Fire.

On August 20, up to 0.5 inches of rain fell over the burn area, further helping the firefight, and on August 24, the Dome Fire was declared 100% contained.^[5] The fire's advance was stopped at Morning Star Mine Road to the east, Powerline Road to the south, near Aiken Mine Road to the west, and near the intersection of Cima Road and Zinc Mine Road south of Striped Mountain to the north.

Cultural

The fire burned in an unpopulated area, but destroyed multiple structures dating back to the Rock Springs Land and Cattle Company ranching operation in the late 19th century, then the second-largest in California. Historic structures that burned included Kessler Springs Historical Ranch House, bunkhouses at Kessler Springs Ranch and Valley View Ranch, and numerous water tanks, troughs, corrals, and other outbuildings. Historic mining operations, such as the Morning Star Mine and Evening Star Mine, were threatened but ultimately spared.^[3]

Ecological

Burned Joshua trees 8 months after the Dome Fire

After the Dome Fire 1.33 million Joshua trees were estimated burned, and of those, less than 200,000 were showing green leaves (meaning a possibility of survival).^[3][5] Scientists affiliated with the Mojave National Preserve attributed much of the intensity of the fire to an increased fuel load; the Cima Dome Joshua tree forest is one of the densest Joshua tree forests in the world.^[5] Preserve scientists suspect this was the result of cattle grazing until the establishment of the preserve in the 1990s. Cattle may have grazed on many other plants but let flammable blackbrush alone, which shielded many Joshua tree seedlings. The eventual combination of blackbrush, flammable invasive species like red brome, and dense Joshua tree stands led to a wildfire-receptive ecology.^[5]

The death of so many Joshua trees, which are native only to the southwestern United States, led to concern about the species' vulnerability to climate change and other pressures.^[12] Joshua trees are split into two varieties—an eastern and a western—and while the Cima Dome population was of the less-threatened eastern kind, the western species was, at the time, a candidate for threatened status under the California Endangered Species Act, though it did not ultimately become listed as such.^[13]

The Mojave National Preserve's lead wildlife biologist estimated that small animal mortality had been low, under 20% for small reptile and mammal species such as snakes, lizards, and rabbits. The Dome Fire also burned in areas considered habitat for the desert tortoise, a critically endangered species, but "no direct tortoise mortality" was found during or after the fire in surveys, and total mortality was estimated at "perhaps a dozen individuals."^[3]