As devastating as it may appear, fire is a natural process, and Joshua Tree National Park has endured centuries of lightning-caused fires. Historically, fires in this area of the Mojave desert were limited in extent because shrubs and trees are widely spaced in deserts and grasses are not abundant. However, human activities may be contributing to increased frequency and severity of fires.
The park maintains records of fires dating back to 1945. Most of these fires occurred between May 18 and September 20 when desert vegetation was very dry. Seventy-four percent of the fires were ignited by lightning. The remaining 26 percent were human caused.
The number and intensity of lightning fires has increased over the past 50 years. Before 1965 most lightning fires burned less than one-quarter acre. After 1965 more large fires and more frequent fires have been recorded. In 1979 the Quail Mountain fire burned 6,000 acres; in 1995 the Covington fire burned 5,158 acres. And in 1999, the largest fire in Joshua Tree’s history, the Juniper Complex fire burned 13,894 acres of slow-growing California junipers, pinyon pines, and Joshua trees.
Though most fires in the park are started by natural causes, fires now spread faster and burn more intensely because of the introduction of non-native plant species. Many of these invasive plants are fast-growing annuals that fill in the areas between shrubs. When they dry out in the heat of summer, these non-natives serve as a fuel source that allow fires to spread.
Desert plants do not need fire to reproduce and many are highly susceptible to fire. The desert does grow back but recovery after a fire is slow. Joshua trees frequently resprout after a fire, but because they are more susceptible to drought and rodents eating their bark, they often die. Even small shrubs like blackbrush may require 50 years to return to pre-fire densities. Also, non-native grasses are quick to invade burned areas and usurp the habitat of native vegetation.
The key to managing fire in Joshua Tree is in understanding how wildfires affect vegetation and wildlife in a desert environment. Biologists are monitoring the long-term consequences of fire in desert ecosystems, as well as the effectiveness of treatments designed to hasten recovery.
To help preserve and protect wildlife, scenery, and natural processes, each park develops its own Fire Management Plan. At Joshua Tree, our current plan provides for full suppression of all fires, including those naturally caused, until we have a better understanding of fire behavior and fire effects in the park and across the Mojave Desert.