Zombie Forest Fires and Climate Change
Zombie forest fires and climate chnage, Researchers report online May 19 in Nature that the first wide scientific examination of overwintering “zombie fires” finds that these rare occurrences can flare up the year after warmer-than-normal summers and account for up to 38 percent of total burn area in some places.
As climate change accelerates in boreal forests, the frequency of zombie fires may increase, causing more greenhouse gases to be released from the region’s soils, which may contain twice as much carbon as the atmosphere.
Zombie fires are hibernating underground. They smolder in the snow over the winter, thriving on the carbon-rich fuel of peat and boreal soil and moving slowly — only 100 to 500 meters over the course of the winter.
The fires resurface near the forest they previously scorched in the spring, burning new fuel even before the traditional fire season begins. These zombie fires have remained a mystery to science until recently, with most information coming from firefighter anecdotes.
Earth systems scientist Rebecca Scholten and her colleagues, on the other hand, were intrigued by strange coincidences in satellite photos. “My adviser noted that new flames were starting extremely close to the previous year’s fire in some years,” Scholten of Vrije University Amsterdam explains.
She claims that this is unique because boreal fires are usually ignited by lightning or human action. The researchers wondered how often fires overwinter when local fire officials confirmed that these were the same flames.
To find evidence of underground fires, the researchers combined firefighter reports with satellite images of Alaska and northern Canada captured from 2002 to 2018. They looked for blazes that started close to the scars left the previous year and that began before midsummer, when lightning-sparked fires usually occur.
The team found that zombie fires are rare, accounting for 0.8 percent of the total area burned by forest fires in these regions over those 16 years, but there was lots of variability. In 2008, one zombie fire burned approximately 13,700 hectares in Alaska, about 38 percent of all burned areas that year in that state.
Zombie fires were more likely to occur, and burn larger swaths of land, after warmer summers that allowed fires to reach deeper into the soil, the researchers found.
Boreal forests are warming faster that the global average and “we’re seeing more hot summers and more large fires and intense burning,” Scholten says. That might set the stage for zombie fires to play a bigger role.
“This is a really welcome advance which could help fire management,” says Jessica McCarty, a geographer at Miami University in Oxford, Ohio, who wasn’t involved in the study. Understanding when zombie fires are more likely to occur could help firefighters identify these areas early, she says, protecting fragile landscapes that house a lot of climate warming gases.
“Some of these soils are thousands of years old,” McCarty says. While “areas we thought were fire resistant are now fire prone” due to climate change, she says, better fire management can make a difference. “We’re not helpless
reference – science news