As another wildfire season looms over California, the U.S. Forest Service is running short of the most experienced and elite firefighters in the country — the forestry crews known as hotshots, who travel the nation putting out wildfires, according to interviews with union officials and agency employees.

A combination of low pay, competition from state and local fire departments and exhaustion from fire seasons that are longer and more devastating than in the past has eroded the federal government’s ability to hire new firefighters and retain the most skilled. Nowhere is this more true than in California, where entry-level Forest Service firefighters in certain parts of the state earn less than the minimum wage of $14 an hour, and staffing levels have plummeted ahead of a fire season that scientists say could be especially active.

Roughly 30% of the federal hotshot crews that work on the front lines of wildfires in California are understaffed, according to the union that represents most Forest Service employees. Some of these typically 20-person crews have lost so many veteran firefighters that the remaining workers have been assigned to lower-ranking Type 2 crews, which don’t require as much experience, union officials said.