As of September 15, 2021, 5.6 million acres — an area about the size of New Jersey — burned in wildfires, according to data compiled by the National Interagency Fire Center (NIFC). Wildfires from the last 10 years burned more than twice as many acres on average as fires in the 1980s.
How often do wildfires occur and how big do they get?
NIFC defines wildfires as any “unplanned and unwanted” fire that begins in an undeveloped location.
The number of wildfires nationwide varies widely each year. There were 74,126 recorded in 2011 and 58,950 in 2020. The amount of land burned also varies year to year, with about 4.6 million acres burned in 2019 and over 10 million acres — an area slightly larger than Massachusetts and Connecticut combined — in 2020.
While the number of fires and acreage burned can vary greatly from year to year, the data from 1983 to now reveals a few key trends.
The total number of acres burned in wildfires have increased in recent decades. The average for 2011–2020 was about 7.5 million acres, slightly larger than Hawaii. That’s more than twice as much as the 10-year average of 2.7 million acres from 1983–1992.
The average number of acres burned has been increasing since 1983.
With fires occurring less frequently but burning up more acres, the average wildfire is more destructive. Between 1983 and 1992, the average wildfire affected 47 acres of land, the size of 35 football fields. Between 2011 and 2020, the average fire affected 119 acres, around 90 football fields.
Wildfires are decreasing but average acres burned per fire has increased.
More than half of the nearly 75.3 million total acres burned in wildfires between 2011 and 2020 were in five states. Alaska and California had more than 10% of all acres burned, 15% and 14.6% respectively. Oregon (8.8%), Idaho (8%), and Texas (7%) were the other three.
Alaska leads in most acres burned during the last decade.
The NIFC classifies wildfires based on ignition sources, the two primary sources being lightning strikes and humans. A wildfire is human-caused if it begins via “debris burning, campfires, arson, discarded smoking products, sparks from equipment in operation, arced power lines, and other means,” according to NIFC.
Between 2011 and 2020, 87.4% of wildfires were classified as human-caused, while lightning strikes caused the rest. However, wildfires from lightning are more destructive than human sources. Over those 10 years, 54.5% of the acres burned in wildfires were caused by lightning.
Wildfires caused by humans are more common than fires caused by lightning.