A report by the Cooperative Institute for Research in Environmental Sciences (CIRES) Earth Lab has illustrated how wildfires have increased in size, frequency and coverage across the USA since 2000. Not only have these fires become more common but they have also spread into new areas, affecting land that previously did not burn.
Virginia Iglesias, a research scientist with the CIRES Earth Lab and lead author of the paper, said, “Projected changes in climate, fuel and ignitions suggest that we’ll see more and larger fires in the future. Our analyses show that those changes are already happening.”
To evaluate how the size, frequency and extent of fires have changed in the USA, Iglesias and her colleagues analyzed data from more than 28,000 fires that occurred between 1984 and 2018 from the Monitoring Trends in Burn Severity (MTBS) dataset, which combines satellite imagery with the best available state and federal fire history records.
The team found that there were more fires across all regions in the contiguous United States from 2005 to 2018 compared with the previous two decades. In the West and East, fire frequency doubled; in the Great Plains, fire frequency quadrupled. As a result, the amount of land burned each year increased from a median of 4,019 to 14,249km2 in the West and from 1,204 to 3,354km2 in the Great Plains.
The researchers also took a closer look at the most extreme fire events in each region. They found that in the West and Great Plains, the largest wildfires grew bigger and ignited more often in the 2000s. Throughout the record, large fires were more likely to occur around the same time as other large fires.
“More and larger co-occurring fires are already altering vegetation composition and structure, snowpack and water supply to our communities,” Iglesias explained. “This trend is challenging fire-suppression efforts and threatening the lives, health and homes of millions of Americans.”
Finally, the team discovered that the size of fire-prone areas increased in all regions of the contiguous United States in the 2000s, meaning that not only is the distance between individual fires getting smaller than it was in the previous decades, but also that fires are spreading into areas that did not burn in the past.
These results confirm a palpable change in fire dynamics that has been suspected by the media, public and fire-fighting officials. Unfortunately, the results also align with other troubling risk trends, such as the fact that the development of natural hazard zones is also increasing wildfire risk. “These convergent trends, more large fires plus intensifying development, mean that the worst fire disasters are still to come,” said co-author and Earth Lab deputy director, William Travis.
The study authors suggest that to adapt and build resilience to wildfire impacts, planners and stakeholders must account for how fire is changing and how it is affecting vulnerable ecosystems and communities.
To read the full report published in the journal Science Advances, click here.