Humans were responsible for igniting 97% of wildfires that threatened homes between 1992 and 2015, according to a University of Colorado Boulder-led study published Monday.

The fires were caused by activities including debris burning, equipment use and arson.

The study also found that between 1992 and 2015, 32 million homes were built in the wildland-urban interface, the site of one-third of all wildfire ignitions. One million homes sat within the boundaries of wildfires in the last 24 years, five times the previous estimates.

“We have vastly underestimated the wildfire risk to our homes,” said lead author Nathan Mietkiewicz in a statement. “We’ve been living with wildfire risk that we haven’t fully understood.”

This wildfire season has been particularly devastating for Colorado as two of the top five largest wildfires in the state’s history, Cameron Peak and Pine Gulch, are currently burning.

At least two of Colorado’s top five largest wildfires were human-caused, as reported by the Denver Post.

The study also found that humans caused 85% of all wildfires in very low-density housing areas and 59% of all wildfires in wildlands from 1992 to 2015. Human-started wildfires accounted for approximately one-third of all firefighting costs in those years.

“Our fire problem is not going away anytime soon,” said co-author Jennifer Balch in a statement.

Balch also pointed to warmer, drier conditions caused by climate change.

The Colorado Department of Agriculture announced Thursday that drought conditions cover 99% of the state.

“(The study) provides greater justification that prescribed burns, where safe, can mitigate the risk and threat of future wildfires,” Balch said. “We essentially need to build better and burn better.”

The full study was published in the journal “Fire,” available at mdpi.com.