Costs mount as fast-moving fires hit northern Calif.

Josh Edelson | AFP | Getty Images

A firefighter douses flames from a backfire while battling the Butte fire near San Andreas, California on September 12, 2015. Wildfires have spread rapidly through northern California, destroying hundreds of homes, forcing thousands of people to flee and injuring four firefighters.

Thousands of acres were burned across northern California over the weekend by a number of fast-moving wildfires that destroyed homes and businesses and forced thousands to flee the inferno.

The Valley fire in Lake County, which is northwest of Sacramento, has burned more than 50,000 acres, according to NBC News. The blaze spread quickly since it started on Saturday from 50 acres to 400 around 4 p.m., and to its current size Sunday afternoon.

Whole towns were ordered to evacuate in the face of the oncoming blaze that had already burned more than 400 homes along 35-mile stretch of highway. "In some cases residents only had minutes to evacuate," said a spokesman for the California Department of Forestry and Fire Protection (Cal Fire).

The Valley fire is just one of seven currently raging across California, according to the USDA Forest Service. More land has burned year-to-date in 2015 than at anytime in the past decade and this year is on track to be the most-burned in 30 years.

Fighting fires isn't cheap. Suppressing wildfires requires hotshot crews, tankers and helicopters to drop chemicals and water to battle the flames.

This year, the Forest Service, which is in charge of much of the nation's fire-fighting efforts, has a budget of $708 million for fire suppression and another $303 million in a special account created in 2009 for fire fighting. The overall fire-management budget is up about 60 percent from a decade ago, for $2.5 billion.

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Even with escalated funding, it probably won't be enough. As of mid-August, about $830 million had gone to suppression.

Costs have overshot the budget in 10 of the last 13 years, according Forest Service spokesperson Jennifer Jones. And this has been a problem for a while: From 1990 to 2003, fire suppression costs exceeded appropriations for all government agencies nearly every year, according to a U.S. General Accounting Office report.

Part of the problem is the way the Forest Service budget is calculated—the service requests a percentage of the 10-year rolling average of previous years' costs, and fires have grown faster than that rolling average has allowed.

"We're using a backwards-looking budget to address unprecedented challenges," said Jones. "We're facing such more difficult fire seasons now—we're facing droughts and record high temperatures. It just takes more suppression assets to get a hold of those fires."

If the administration has its way, future costs for the largest fires could come from FEMA, the way other natural disasters like hurricanes and floods are handled.

Johs Edelson | AFP | Getty Images

Burned out vehicles are surrounded by smoldering rubble while firefighters continue to battle the Valley fire in Middletown, California on September 13, 2015. The governor of California declared a state of emergency Sunday as raging wildfires spread in the northern part of the drought-ridden US state, forcing thousands to flee the flames.

"I don't think anybody doubts that the cost of fighting fires has gone up," said Debbie Miley, executive director of the National Wildfire Suppression Association (NWSA), a trade group for private wildfire fighters. "We believe that they should apply for that funding after it's spent versus having it up front."

In fiscal year 2014, the Forest Service spent about $1.2 billion on fire suppression, and more than 40 percent of that—$502 million—went to private contractors, according to Jones. That includes the ground crews and other service providers represented by the NWSA, as well as more than $300 million for contract air tankers and helicopters. (it doesn't include contracts with other agencies or states). Contractors are relied upon to fill in when government staff and resources have been stretched thin.

Another part of the increase in costs is more homes in the line of danger.

According to a study by Headwaters Economics, 60 percent of homes that have been built since 1990 have been in the "wildland-urban interface," the areas where America's wild areas and residential areas meet, converting areas that could have safely burned into areas that need to be fiercely protected at a rate of about 4,000 acres a day.

Keeping those homes from burning accounts for between 30 percent and 95 percent of firefighting costs—depending on who you ask. And it's only going to get worse as we expand our living space into the backcountry.

By Sunday afternoon, the Butte fire, another Northern California blaze, had destroyed more than 100 buildings and threatened about 6,400 more, according to NBC News.

Sacramento police tweet.

According to a 2015 report by CoreLogic, in the western U.S. alone there are now more than 897,000 residential properties in areas that are at high or very high risk for wildfires. If destroyed, those homes would cost $237 billion to rebuild.

The agencies laboring to protect more and more private homes from bigger and more severe fires are being consumed themselves by the costs. For the first time this year, more than half of the Forest Service's budget is for wildfires, far up from 16 percent in 1995, according a report released by the department in August. Non-fire employees have been cut by 39 percent over that time.

Not only have non-fire-related programs like watershed management, road improvement and other responsibilities tied to the National Forest System been pillaged for fire suppression funds, but in years when the fire suppression budget is inadequate, the Forest Service must transfer money from other programs to cover the costs. In some years, that shortfall has approached another $1 billion.

Sometimes that money comes from preventative efforts like clearing vegetation and proscriptive fires, which are designed to help control future fires. That's only going to make things worse in the future.

"The current method isn't working, and it's very disruptive," said Jones. "When we start depleting our firefighting funds, we have to go out to the field units and say stop spending—we take money away from wildlife projects and road projects and it hurts long-term efforts to reduce fire risks on the front end."