Driven by climate change, lightning storms spark more fires in boreal forests, new study says

A new NASA-funded study led by Sander Veraverbeke, professor at Vrije Universiteit Amsterdam, finds that extreme lightning storms linked to climate change were the main driver of recent massive fire years in Alaska and northern Canada, with the fires creeping farther North, potentially altering Northern landscapes.

06/27/2017 | 11:34 AM

A team led by Sander Veraverbeke analyzed satellite images and data from ground-based lightning networks to study the cause of the fires, whose numbers have been increasing in recent years. Record numbers of fires occurred in the Canadian Northwest Territories in 2014 and in Alaska in 2015. They found increases between two and five percent a year in the number of lightning-ignited fires since 1975. Results of the study are published in Nature Climate Change.

Veraverbeke said that while the drivers of large fire years in the high North are still poorly understood, climate change is clearly playing a role. “We found that it is not just a matter of more burning with higher temperatures. The reality is more complex: higher temperatures also spur more thunderstorms. Lightning from these thunderstorms is what has been igniting many more fires in these recent extreme events,” Veraverbeke said. “These trends are likely to continue,” said study co-author Brendan Rogers at Woods Hole Research Center in Falmouth, Massachusetts. “We expect an increasing number of thunderstorms, and hence fires, across the high latitudes in the coming decades as a result of climate change.” This is confirmed in the study by different climate model outputs. Study co-author Charles Miller of NASA’s Jet Propulsion Laboratory in Pasadena, California, said while data from the lightning networks were critical to this study, it is challenging to use these data for trend detection because of continuing network upgrades. “A spaceborne sensor that provides lightning data at high latitudes that can be linked with fire dynamics would be a major step forward,” he said.

The researchers found that the fires are creeping farther North, near the transition from boreal forests to Arctic tundra. “In these high-latitude ecosystems, permafrost soils store large amounts of carbon that become vulnerable after fires pass through,” said co-author James Randerson, professor at the University of California, Irvine. “Exposed minerals in soils after tundra fires also provide favorable seedbeds for trees migrating North under a warmer climate.” “Taken together we discovered a complex feedback loop between climate, lightning, fires, carbon and forests that may quickly alter northern landscapes,” Veraverbeke concluded. “A better understanding of these relationships is critical to better predict future influences from climate on fires, and from fires on climate.”

The Alaska Fire Science Consortium at the University of Alaska, Fairbanks, also participated in the study.

Photo:

A wildfire burns in an Alaskan boreal forest as convective clouds tower overhead (credit BLM Alaska Fire Service)