Wildfires across the United States have gotten four times larger, occur three times more frequently since 2000 and affect areas not traditionally at risk from disaster, according to a new paper from researchers at the University of Colorado Boulder.

Published on Wednesday in Science Advances, the paper indicates that larger fires have become more common but are also affecting communities that were previously not at risk for wildfires. Researchers said this confirmed climate change has affected fire activity and could worsen in the coming years. 

“Projected changes in climate, fuel and ignitions suggest that we’ll see more and larger fires in the future,” said Virgina Iglesias, a researcher with the university’s Earth Lab and lead author of the paper. “Our analyses show that those changes are already happening.”

Iglesias and her fellow researchers examined data from over 28,000 wildfire that occurred between 1984 and 2018. The data used is from the Monitoring Trends in Burn Severity dataset, which combines satellite imagery with the best available state and federal fire history records, according to the university.

The research team found that more fires happened in the United States between 2005 and 2018 when compared to the previous two decades. In the west specifically, the frequency of fires doubled, according to the report.

Due to the increase in frequency of fires, the amount of land burned each year in the west grew 255%, with the square miles burned skyrocketing from 1,552-square-miles to 5,502-square-miles during the 13-year period, the report said. 

In Colorado alone, the state’s 20 largest wildfires have ignited since 2002, according to the Colorado Division of Fire Prevention & Control.

Additionally, the state’s five most destructive fires on record have all occurred since 2013, the most recent of which is the Marshall Fire, which ignited on Dec. 31 and destroyed nearly 1,100 homes.

But the western United States isn’t the only region affected. Fire frequency quadrupled in the Great Plains region, resulting in a 178% increase in land burned each year.

Besides destroying businesses, homes and lives, the fires are also affecting the environment, Iglesias said.

“More and larger co-occurring fires are already altering vegetation composition and structure, snowpack, and water supply to our communities,” Iglesias said. “This trend is challenging fire-suppression efforts and threatening the lives, health and homes of millions of Americans.”

Researchers also discovered that the size of fire-prone areas is increasing, as there is less distance between individual fires, according to the report. 

This means more areas of the county — previously not at-risk of wildfire — are now potentially at risk. Researchers said the discovery is “troublesome,” as the trend aligns with other risk trends, such as the increase of urban development, which is also exposing more areas to the natural hazard zone.

William Travis, co-author of the study and Earth Lab’s deputy director, said more devastating fires could be on the horizon.  

“These convergent trends, more large fires plus intensifying development, mean that the worst fire disasters are still to come,” he said. 

Researchers said in order to combat larger fires, local municipalities, planners and stakeholders must take into consideration these changes when planning for disasters.

“Adaptation to these emerging regimes requires that we rethink our priorities for action, especially given large discrepancies in ecological and social vulnerability,” researchers wrote.