What the wildfires are costing us

It's not your imagination—forest fires really are getting worse.

As of this week, more than seven million acres of American land have been scorched by wildfires this year. That's about the size of Massachusetts, and more than any other year at this point of the season, in at least the last decade. This week, active duty military personnel were mobilized to help fight fires for the first time since 2006.

Vast swaths of America are on fire—there are currently about 95 large fires active across 10 states—but this year is no anomaly. The number of wildfires touching more than 50,000 acres has been increasing over the last 30 years, and the total acreage burned this decade is more than double the area burned in the 1990s.

And fighting fires isn't cheap. Suppressing wildfires requires hotshot teams, hand crews and tankers and helicopters to dump chemicals to keep the flames at bay.

This year, the Forest Service, which is responsible for most of the country'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 of $2.5 billion is up about 60 percent from a decade ago.

Even with escalated funding, it probably won't be enough. Already this year, about $830 million has 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.

Read MoreWildfires across 6 states

"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.

But why are fires getting so much worse in the first place? Within our lifetimes, fire seasons have grown much longer (not just in the U.S., but across the globe). The size and severity of those fires has increased with climate change as drought and hazardous fuel buildups have turned whole states into tinderboxes.

A decade of wildfires -- percentage acres burned by state

It's the biggest fires that cost the most. About 2 percent of all fires consume more than 90 percent of the overall wildfire suppression budget. But it's not just size that matters—the average cost of fighting fires per acre burned is also much higher than it was a few decades ago.

"One reason [costs] have gone up is inflation, and we have had more fires that tend to burn longer," said Jessica Gardetto, spokesperson for the National Interagency Fire Center. "Some fires will burn for months for a time, so the suppression budgets need to be larger."

Part of that increase is also the cost of protecting our homes, which we are building in areas that are at risk for wildfire damage. 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.

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 this month. 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."