Thousands of federal firefighters could face substantial pay cuts in the coming weeks, potentially hampering the country’s ability to respond to wildfires as they have grown more severe.

Federal wild-land firefighters received a temporary boost to their paychecks last year, which was meant to help strained agencies offer more competitive wages to recruit and retain workers. But funding for the pay raises is set to run dry next month, and federal officials have warned that more firefighters will leave for higher-paying jobs if their salaries are slashed.

In 2021, President Biden raised the minimum wage for wild-land firefighters to $15 an hour from $13. Congress then agreed to increase firefighter pay by either 50 percent of a worker’s base salary or $20,000 a year, whichever was lower.

The typical base salary for an entry-level wild-land firefighter is about $34,000 without the supplement, according to Agriculture Department data. Many also rely on overtime pay to boost their incomes.

The National Federation of Federal Employees, which represents about 10,000 wild-land firefighters, has estimated that 30 to 50 percent of the work force could resign if salary increases end.

Mike Alba, 43, an assistant engine captain residing in Santa Clarita, Calif., said he would have to go back to “living paycheck to paycheck” if his annual base pay dropped to about $52,000 from $72,000. He said the pay increase has allowed him to spend more time with his two children because he has felt less pressure to work extra hours, but he would probably quit if his salary was reduced.

“I would have to work twice as hard just to make ends meet,” said Mr. Alba, who has worked for the Forest Service for more than a decade.

Mr. Alba said his station was already struggling to fill three open positions and two firefighters recently left to take jobs at state and municipal fire departments.

“If we can’t staff, that means we can’t go to fires,” Mr. Alba said. “That means loss of property. It could mean loss of life.”

A temporary spending measure to keep the government funded allows federal officials to tap into other funding sources to continue paying the salary supplement through mid-November, but officials said that fell short of a permanent solution.

“Without a permanent pay fix that creates certainty for our federal firefighters at both the Forest Service and the Department of the Interior, we will continue to see wild-land firefighters leave their jobs for other, higher-paying jobs,” a representative for the Agriculture Department, which oversees the U.S. Forest Service, said in a statement.

The Forest Service, which employs roughly 11,000 seasonal and permanent wild-land firefighters, previously estimated that funding would run out around the beginning of November. Officials at the Interior Department, which employs about 5,000 wild-land fire personnel, also said the funding was set to run out around then.

Representative Joe Neguse, a Colorado Democrat and co-chairman of the Bipartisan Wildfire Caucus, has introduced bipartisan legislation that would permanently increase federal firefighter pay, but the measure has so far stalled in the House.

“I’m deeply concerned about the inability of Congress to muster the political will to get this done,” Mr. Neguse said. “The reality is that our wild-land firefighters are woefully undercompensated.”

Randy Erwin, the president of the National Federation of Federal Employees, said he felt “reasonably confident” that pay increases would be made permanent, but the Republican push for spending cuts made that outcome more uncertain and many firefighters were already departing or crafting contingency plans.

“They’re going to be leaving in droves,” Mr. Erwin said. “It’s a really scary thing to think that we won’t have the necessary personnel to contain wildfire in this country.”

Chris Hensley, 36, a federal firefighter in southwest Colorado, said he was able to save up to buy a house last month because his annual base pay rose to $60,000. He said he worried about affording his mortgage payments if his base pay dropped to $40,000, but he planned to stay at his position for now.

“Taking care of the forest health is something that we all take a lot of pride in, so it keeps us here,” he said.

Still, Mr. Hensley said he would consider leaving because he could easily earn more or a similar amount elsewhere. “If they can’t figure it out and keep paying us what they’re paying us now,” he said, “I could go work at the local pizza shop.”