Why are some vegetation fires allowed to burn? - A fire burns at Ranges 108 and 109 on Marine Corps Base Camp Pendleton, California, June 12, 2019. The Camp Pendleton Fire Department encounters several wildfires each year, some of which they will let burn in order to prevent larger fires in the future. The firefighters will also avoid fighting a fire if there's a potential for unexploded ordnance to be in the area, and will instead monitor the blaze until it goes out. (U.S. Marine Corps photo by Lance Cpl. Drake Nickels)

U.S. Marines with 1st Law Enforcement Battalion, I Marine Information Group, inspect an M2 Browning .50 caliber machine gun during a training exercise on Camp Pendleton, Calif., Oct. 24, 2017.The importance of this exercise was to prepare the Marines for their upcoming deployment with the 13th Marine Expeditionary Unit. - U.S. Marines with 1st Law Enforcement Battalion, I Marine Information Group, fire a M240B machine gun during a night live fire training exercise on Camp Pendleton, Calif., Oct. 24, 2017.The importance of this exercise was to prepare the Marines for their upcoming deployment with the 13th Marine Expeditionary Unit. (U.S. Marine Corps photo by LCpl Anabel Abreu Rodriguez)

Construction Battalion Maintenance Unit 303, San Diego is working to reconstruct the San Mateo Live-Fire Training Convoy Course on Marine Corps Base Camp Pendleton, May 17. One and a half mile of this five-mile long training course has a six percent grade, making it one of the steepest roads on base. Extreme erosion due to heavy rain and excessive use made this road increasingly perilous to navigate. - Construction Battalion Maintenance Unit 303, San Diego is working to reconstruct the San Mateo Live-Fire Training Convoy Course on Marine Corps Base Camp Pendleton, May 17. One and a half mile of this five-mile long training course has a six percent grade, making it one of the steepest roads on base. Extreme erosion due to heavy rain and excessive use made this road increasingly perilous to navigate.