Wildfire seasons all over the planet are lasting longer than they have in the past and burning wider swaths of land, and Earth's changing climate is to blame, according to a new report.
Ecologist and fire scientist Matt Jolly and his colleagues say the average duration of annual wildfire seasons lengthened almost 20 percent between 1979 and 2013, and the amount of land vulnerable to burning almost doubled. (Tweet This). The team published its results in the journal Nature Communications this week.
The phenomenon isn't just happening in areas such as the Western United States. Wildfires are burning for a longer period of time on every continent except Australia and Antarctica, the report said. Forests and grasslands in Africa are burning more, and the fire season in South American tropical forests is more than a month longer than it used to be.
Fires are also getting worse across the Eastern U.S. coastal plain, and they increased the most in the Northern Rocky Mountain region.
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The study also shows that the length of the wildfire season correlates closely with changes in temperature, humidity, rainfall, and other climate indicators.
Wildfire seasons tend to fall in hotter and drier times of the year, when vegetation is vulnerable to burning. Causes vary: Lightning is a frequent cause of wildfires in remote wilderness areas, but the National Parks Service says that up to 90 percent of wildfires in the United States are caused by people.
When they occur naturally, wildfires are not necessarily a problem; occasionally scorching a section of land allows new plants to grow, which can provide fresh food sources for wildlife.
But wildland fires are increasingly destructive and costly in terms of lives and property, requiring substantial investments in wildfire suppression.
"Recently, there has been a surge of extremely destructive fires with corresponding social disruptions and substantial economic costs," the researchers wrote in their paper.
Fighting wildfires on federal land costs the United States $1.7 billion a year, according to figures cited in the paper. Canada spends about $1 billion annually suppressing fires on its public land. But those numbers likely do not account for all of the ancillary costs around fighting wildfires, according to the study's authors.
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"When all components are considered, including preparedness/suppression costs and economic losses, these total costs are substantially higher," the researchers wrote.
For example, Australia spent nearly $10 billion—1.3 percent of its total GDP—suppressing dangerous wildfires in 2005, according to the report.
The report also notes that wildfires may be be pumping even more carbon into the atmosphere, furthering the very changes in climate that are producing more wildfires.