DENVER -- As Colorado's wildfires continue to grow in size, so do the costs of fighting them.
The running tab to suppress the state's forest fires has now topped $40 million this summer. More than $33 million of that has been spent on just two fires.
The 416 fire burning near Durango has cost $27.8 million so far. The state's largest fire, the Spring Fire in Southern Colorado, has cost $6.5 million so far, but the number is expected to skyrocket before the fire is extinguished.
The Spring Fire has already destroyed more than 100 homes and is nowhere close to being contained.
"It's close to homes. It's close to infrastructure, and that's what drives the costs up quite a bit," said Larry Helmrick, with the Rocky Mountain Fire Coordination Center.
Nationwide, more than $2 billion was spent fighting wildfires in 2017. It's a number that rises almost every year.
In 1991, just 13 percent of the U.S. Forest Service's budget was spent on wildfire suppression. It topped 50 percent for the first time ever in 2015. The agency estimates that number will increase to 67 percent by 2025.
"It is what it is. When we go out there we`re facing all kinds of things," said Helmrick.
There are several reasons fires cost so much more than they used to. First, there's more of them. The fire season in Colorado is 60 to 80 days longer than it was three decades ago.
"It`s 12 months a year. That's the way we look at it now," said Helmrick.
More resources are also now used to fight fires. That includes helicopter and planes. Nationally, the aerial support devoted to firefighting is three times the amount used three decades ago.
"With those amount of aircraft it's going to drive the costs up, but it's needed," said Helmrick.
Helmrick says there are currently 70 to 80 aircraft being used on the fires in Colorado.