Lightning Threatens Boreal Forests: Climate Change Elevates Wildfire Risks, Imperiling Carbon Reserves

A recent study accentuates the escalating peril of wildfires ignited by lightning in boreal forests, a consequence of climate change. This collaborative global research, leveraging machine learning, pinpoints lightning as the predominant initiator of fires in untouched extratropical forests. This contrasts with the human-induced fires in tropical areas. Predictions from climate models suggest a notable rise in lightning occurrences with increasing global temperatures, thereby heightening the likelihood of severe wildfires.

The findings signal a heightened risk of such wildfires in boreal forests, which could further intensify global warming by destabilizing the substantial carbon deposits in these areas.

The study, spearheaded by Dr. Declan Finney from the School of Earth and Environment, involved collaboration with experts from Vrije Universiteit Amsterdam, Jiangsu Academy of Agricultural Sciences, the University of East Anglia, and BeZero Carbon Ltd.

Published on November 9 in Nature Geoscience, the article titled “Extratropical forests increasingly at risk of lightning fires” sheds new light on this subject.

Leveraging Machine Learning to Analyze Wildfires

The researchers employed machine learning to ascertain the primary causes of wildfire ignitions – whether human or natural (lightning) – across various global regions. The algorithm was refined using data from seven distinct regions to enhance its predictive accuracy.

This study is groundbreaking in its global attribution of fire ignition sources.

It reveals that 77% of the burn areas in pristine extratropical forests are due to lightning, in stark contrast to the predominantly human-caused fires in tropical forests.

Intact extratropical forests, characterized by minimal human activity and small populations, are largely found in remote boreal areas.

Examining Climate Change’s Influence on Lightning Incidence

The researchers also utilized climate models to explore the potential changes in lightning frequency as global temperatures rise.

Findings indicate an 11 to 31 percent increase in lightning frequency per degree of global warming over these untouched extratropical forests, implying more wildfire ignitions due to climate change.

Wildfires caused by lightning are typically larger, more intense, and confined to remote areas during times of extreme fuel dryness, compared to those caused by humans.

Previous studies by the team have demonstrated increasing frequency and intensity of fire-prone weather conditions as the climate warms, leading to more flammable forests.

This increased flammability, coupled with the rising incidence of lightning, signals an escalating wildfire threat for intact extratropical forests in the future.

Dr. Finney, an authority on lightning and climate change, remarked:

“This research underscores lightning’s crucial role in ecosystems and global carbon storage. Often, we consider lightning’s impact on humans, but it’s also a key wildfire ignition source in remote, human-scarce regions, especially in boreal forests, where it can spark wildfires and trigger additional greenhouse gas emissions.”

Carbon Storage and Emissions in Extratropical Forests

These forests are globally significant for their extensive carbon storage in vegetation and permafrost soils.

Approximately 91 percent of these northern hemisphere forests are underlain by permafrost.

Wildfires in these areas release substantial amounts of carbon dioxide and other greenhouse gases, more so than in other regions.

Despite covering only about 1 percent of the Earth’s land surface, fires in these pristine extratropical forests account for over 8 percent of global CO2 emissions from fires.

Projections suggest that by the century’s end, under a moderate emissions scenario, fires could increase greenhouse gas emissions from permafrost thaw by 30 percent.

Dr. Matthew Jones, a Research Fellow at the University of East Anglia specializing in the carbon cycle and climate change, stated: “Extratropical forests play a vital role globally by storing dense carbon reserves in vegetation and soils, aiding in the reduction of atmospheric CO2 and moderating global warming.

“However, wildfires in these regions emit more CO2 per area than almost any other place on Earth.

“Our research emphasizes the vulnerability of extratropical forests to the combined effects of a warmer, drier climate and an increased likelihood of lightning-strike ignitions.

“Rising lightning ignitions pose a risk to the vast carbon stores in extratropical forests, especially as these regions become warmer, drier, and more susceptible to fires.”

A Record-Breaking Fire Season

This research gains relevance in light of Canada’s unprecedented fire season in 2023, where fire emissions were over four times higher than the average from 2003-2022. Initial reports indicate numerous lightning ignitions in Canada this year.

Dr. Thomas Janssen from VU, the study’s lead author, commented: “While our research didn’t directly address Canada’s extreme fire season this year, it aids in comprehending these events.

“Boreal forests are likely to experience more extreme fire seasons in warmer climates due to hotter, drier conditions and increased lightning strikes.”

The authors caution that greenhouse gas emissions from fires can exacerbate atmospheric carbon levels,

Frequently Asked Questions (FAQs) about lightning-induced wildfires

More about lightning-induced wildfires

• Nature Geoscience Article on Boreal Forests
• Dr. Declan Finney’s Research Profile
• University of East Anglia Climate Research
• Vrije Universiteit Amsterdam Environmental Studies
• Jiangsu Academy of Agricultural Sciences
• BeZero Carbon Ltd. Climate Initiatives
• Canadian 2023 Wildfire Season Report
• Machine Learning in Environmental Research
• Climate Change and Lightning Frequency Study
• Permafrost and Carbon Emissions Research