The only natural cause of a fire is lightning. Usually lightning doesn't cause a lot of the fires, but sometimes it will. Most of the time lightning fires will start when there are a lot of tall and large trees. Most people think that a fire in a city would cost way more than a fire in the desert but that is not always true. These fires can escalate into the millions of dollars.
The main cause of desert fires are careless smokers who throw their cigarette butts on the ground without making sure the butt is out. Other causes include unmonitored campfires, grills, and heated car undersides.
When fighting a desert fire you should always suppress the fire pretty quickly. You may want to consider letting it burn if they are not burning as important things. Pretty much they will let it burn to lessen flammability in other years, but they will suppress the fire when appropriate. A thing to note is that if there are livestock grazing nearby it may reduce the fuel for the fire.
River, R ('21) & Collin, C ('21)