Climate change contributes to longer fire seasons worldwide

In late June, smoke from wildfires in Canada streamed down over North Dakota, South Dakota, Minnesota, and Iowa. Photo courtesy NASA Earth Observatory.
In late June, smoke from wildfires in Canada streamed down over North Dakota, South Dakota, Minnesota, and Iowa. Photo courtesy NASA Earth Observatory.

New study tracks regional nuances, global trends

Staff Report

FRISCO — U.S. Forest Service scientists and other researchers say there has been a significant increase in the length of wildfire seasons on nearly every continent, with the exception of Australia. Fire weather seasons around the globe have increased by nearly 20 percent and the global burnable area doubled over the past 35 years.

Most vegetation types, except boreal forests, showed significant increases in the fire weather season length, the new study found. Some areas, such as the Western and Southeastern United States, Alaska, tropical and sub-tropical South America and Eastern Africa and large parts of Eurasia show a steady lengthening of the fire season from 1979-2013.

The research team included scientists from South Dakota State University, the Desert Research Institute and the University of Tasmania, Australia. The findings have been published in the  journal Nature Communications.

“If these fire weather changes are coupled with ignition sources and available fuel, they could markedly impact global ecosystems, societies, economies and climate,” the scientists wrote, explaining that wildfires “play a pivotal, dynamic role in terrestrial and atmospheric systems, including greenhouse gas emissions.” In big fire years, annual CO2 emissions can exceed 50 percent of fossil fuel combustion emissions.

Wildfire activity is driven by three key factors; fuels, sources of ignition, and the weather, which includes temperature, relative humidity, precipitation, and wind speed. Of the three factors, weather is the most variable and largest driver of regional burned area.

To try and pinpoint how climate change is affecting wildfire potential, the researchers separated weather from the other factors, said lead scientist Matt Jolly, with the USFS Rocky Mountain Research Station’s Fire Science Lab.

The findings showed some regional variability, but the global trend was clear cut.

“Although Australia and boreal forests showed no significant fire season length trends, we identified regional increases in the frequency of unusually long fire seasons in those regions since the mid-1990s,” Jolly said.

“Essentially, while fire seasons aren’t getting consistently longer everywhere, unusually long fire seasons have been more frequent across much of the globe, even in areas such as Australia and the global boreal forests where significant long-term trends were absent,” he said.

The methodology used in this study to explore and explain complex observed variations in fire activity can be applied to any given geographic area whether it is local, regional, national or international. Understanding what is driving the trends can help managers mitigate increased wildfire potential.

NASA Headquarters under the Terrestrial Ecology Program of the NASA Science Mission Directorate’s Earth Science division supported this work. NASA provided additional funding through an applied wildland fire sciences award.

To download a copy of Climate-induced variations in global wildfire danger from 1979 to 2013 go to http://dx.doi.org/10.1038/ncomms8537.

To find out more about the RMRS go to www.fs.fed.us/rmrs. You can also follow on Twitter at www.twitter.com/usfs_rmrs.

 

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