WASHINGTON - In the worst wildfire season on record, the U.S. Department of Agriculture Forest Service ran out of money to pay for firefighters, firetrucks and aircraft that dump retardant on monstrous flames.

So officials did about the only thing they could: take money from other forest-management programs. But many of the programs were aimed at preventing giant fires in the first place, and raiding their budgets meant putting off the removal of dried brush and dead wood over vast stretches of land -- the things that fuel eye-popping blazes, threatening property and lives.

Recently, Congress stepped in and reimbursed the Forest Service and the Interior Department, which plays a far lesser role in fighting fires, with $400 million from the 2013 continuing resolution, allowing fire-prevention work to continue. Forestry experts at state agencies and environmental groups greeted it as good news.

But they also faulted Congress for providing at the start of the fiscal year only about half of the $1 billion it actually cost to fight this year's fires. They argued that the traditional method that members of an appropriations conference committee use to fund wildfire suppression -- averaging the cost of fighting wildfires over the previous 10 years -- is inadequate at a time when climate change is causing longer periods of dryness and drought, giving fires more fuel to burn and resulting in longer wildfire seasons.

Once running from June to September, the season has expanded over the past 10 years to include May and October. It was once rare to see 5 million cumulative acres burn, agriculture officials said. But some recent seasons have recorded millions more than that.

This year's wildfire burn was nearly 8 million acres at the end of August, about the time that the budget allocated to fight them ran dry.

"They knew they were running out of money early on, in May," said Chris Topik, director of North American Forest Restoration for the Nature Conservancy. "They were telling people in May, 'Be careful, don't spend too much [on prevention].'"

Over seven years starting in 2002, $2.2 billion was transferred from other accounts for fire suppression when the budget came up short, according to records provided by the Forest Service. Congress at times reimbursed a fraction of those funds.

"We did have to transfer the money," said Jim Hubbard, deputy chief of state and private forestry for the Forest Service. "It disrupts work during the field season. It was not a major impact this season, but would have been if Congress didn't restore it."

A spokeswoman for the House Appropriations Committee said its chairman, Rep. Harold Rogers, R-Ky., and members "believe that providing adequate funding for wildfire suppression is of the utmost importance. This is why they fought for hundreds of millions in funding in recent ... legislation," as well as in appropriations bills.

Staff members on the committee acknowledged that using the 10-year average cost of wildfire suppression to determine the budget is not ideal. The spokeswoman, Jennifer Hing, said the committee will continue to operate as it has.

Each year that money was removed from brush-disposal and timber-salvage programs, the Forest Service's efforts to prevent fire fell "further and further behind," said Jake Donnay, senior director of forestry for National Association of State Foresters.