Lightning leading cause of wildfires, threatening carbon storage

New research reveals that lightning is the primary cause of wildfires in boreal forests, a crucial carbon storage area. The frequency of these lightning strikes is expected to increase with climate change.

Machine learning predicts wildfires

Dr. Matthew Jones from the University of East Anglia's Tyndall Centre for Climate Change Research led the study which used machine learning to predict global wildfire ignitions and identify their causes. This marks the first time sources of fire ignition have been attributed on a global scale.

The study discovered that lightning caused 77% of burned areas in intact extratropical forests, in contrast to tropical regions where humans predominantly cause fires.

Scientists used climate models to predict changes in lightning frequency with global warming. The study found an 11 to 31% increase in lightning frequency per degree of global warming over these forests, indicating a heightened risk of wildfires due to climate change.

The research also revealed that lightning fires tend to be larger, more intense, and more confined to remote areas during periods of extreme fuel dryness compared to human-caused fires. These fires can have profound effects on the carbon stores in extratropical forests, which contribute over 8% of global CO2 emissions from fires despite covering only about 1% of Earth’s land surface.

Dr. Jones emphasized the global importance of extratropical forests in moderating global warming by storing dense amounts of carbon in vegetation and soils. However, when fires occur in these regions, they emit more CO2 per unit area than virtually anywhere else on Earth.

The research gains relevance in the context of Canada’s record-breaking fire season in 2023, where emissions were over four times the average of the past two decades.

The researchers warn that greenhouse gas emissions from fires can contribute to rising concentrations of carbon in the atmosphere and drive additional warming, further exaggerating the likelihood of fires and other adverse impacts of climate change in the future.

Extratropical forests hold immense carbon

A new study led by Dr. Matthew Jones from the University of East Anglia’s Tyndall Centre for Climate Change Research has found that lightning is the main cause of wildfires in boreal forests, key areas for carbon storage. The frequency of these lightning strikes is predicted to increase with climate change.

The research team used machine learning to predict wildfire ignitions worldwide and to determine their causes, whether human or natural lightning. This signifies the first time attributions of fire ignition sources have occurred on a global scale.

The study revealed that lightning caused 77% of burned areas in intact extratropical forests, a stark contrast to tropical regions where humans predominantly cause fires.

Researchers used climate models to predict changes in lightning frequency with global warming. The study indicated an 11 to 31% increase in lightning frequency per degree of global warming over these forests, suggesting a heightened risk of wildfires due to climate change.

Dr. Jones highlights the global importance of extratropical forests in moderating global warming by storing dense amounts of carbon in vegetation and soils. However, when fires occur in these regions, they emit more CO2 per unit area than virtually anywhere else on Earth.

Record-breaking fire season 

Given Canada's record-breaking fire season in 2023, when fire emissions were more than four times greater than the 2003-2022 average, the research assumes particular timeliness. The researchers warn that greenhouse gas emissions from fires can contribute to rising concentrations of carbon in the atmosphere and drive additional warming, further exaggerating the likelihood of fires and other adverse impacts of climate change in the future.

"Professor Sander Veraverbeke of VU stated that wildfires increase greenhouse gas emissions, which reinforces the problem of climate change. He explained that the climate warming results in more fires, which in turn emit more greenhouse gases."

"Most boreal forests, which underlie carbon-rich permafrost soils that would take many thousands of years to reform if lost to fire, particularly emphasize this 'reinforcing feedback'."

Dr. Finney stated, "We base our thoughts on the research conducted here, along with other recent studies, which steers our focus away from only considering the tropics as the primary regions affected by lightning. We find that an examination of areas closer to the poles raises concerns regarding the potential existence of overlooked climate feedback processes. Making accurate predictions on how lightning will react to climate change remains a high uncertainty. However, we must take the results found here seriously since available evidence has consistently indicated an increase in lightning occurrences in boreal and more polar regions."

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