Average acreage burned in wildfires doubled since 1991

The average acreage burned by wildfires more than doubled between 1991 and 2021, according to a report published Thursday by the Congressional Budget Office (CBO). 

During the period covered by the report, the number of annual wildfires is down slightly, but the acreage burned has soared.

Between 1991 and 2021, the total number fell from some 76,000 to about 59,000. However, about 7 million acres burned in 2021, compared to 3 million acres in 1991. The 2021 acreage was still lower than the previous year, which saw about 10 million acres burned. 

The report also found that between 2016 and 2020, federal spending on wildfire suppression came to $2.5 billion in 2020 dollars. 

During the 30-year period covered by the report, the majority of acreage burned was federal land for all but five years, between 50 and 70 percent in most cases, although more individual fires were on nonfederal lands. Fires on federal lands are typically bigger than those on privately owned land or land owned by state or local governments.  

The CBO attributed much of this disparity to the fact that fires on public lands are often in remote, sparsely populated areas that are considered less of a priority to extinguish.

Of the 495,000 fires on federal lands between 1991 and 2021, the average size was 225 acres, compared to an average of 45 acres for the 1.8 million fires on other lands during the same period. Both categories of fire grew in size on average during those three decades, with those on federal lands nearly quadrupling in acreage, compared to a smaller growth of about two times for other lands. 

The majority of fires bigger than 40,000 acres were in the western United States., according to the CBO. Since 2010, the acreage burned has been smaller for plains and Rocky Mountain states than for those along the West Coast.

Meanwhile, while southern states are less likely to see bigger fires, those fires in southern states that exceeded 40,000 acres burned more than Pacific and Mountain West states combined in 2011. The CBO attributed this phenomenon to an unusually dry spring in the South that year, as well as a number of large fires in South Texas.  

Increasing temperatures have been a major factor in the overall upward trend, according to the CBO. Since 1990, temperatures have topped the historical average across the continent nearly every year, and the area west of the Rocky Mountains has seen atypically dry conditions for much of the year for most of the last two years.