Boreal forests, known for their crucial role in carbon storage, are facing an alarming increase in the frequency of wildfire ignitions caused by lightning strikes. A research paper published in Nature Geoscience titled “Extratropical forests increasingly at risk of lightning fires” sheds light on this pressing issue. Led by Vrije Universiteit (VU) Amsterdam, in collaboration with the University of Leeds, Jiangsu Academy of Agricultural Sciences, and BeZero Carbon Ltd., the study utilized machine learning techniques to predict global wildfire ignition sources. What sets this study apart is its attribution of fire ignition sources globally. The findings revealed that approximately 77% of burned areas in intact extratropical forests are due to lightning ignitions, a stark contrast to the tropics where human activity plays a more significant role.
Climate change has a direct impact on the frequency of lightning strikes in boreal forests. Climate models were employed to investigate this relationship, highlighting a concerning trend. For every degree of global warming, intact extratropical forests experience an increase of 11 to 31% in lightning frequency. This rise in lightning strikes brings with it a higher risk of more frequent wildfire ignitions. Compared to anthropogenic fires, lightning fires tend to be larger, more intense, and primarily restricted to remote areas and periods of extreme fuel dryness. Disturbingly, both the flammability of forests and the frequency of lightning strikes are synchronously increasing, amplifying the threat of wildfires to intact extratropical forests.
Extratropical forests play a vital role on a global scale as they serve as repositories of substantial carbon reserves within their vegetation and permafrost soils. The permafrost underlying 91% of these forests in the northern hemisphere makes them particularly significant. During forest fires in these regions, significant amounts of carbon dioxide (CO2) and other greenhouse gases are released, surpassing emissions from fires occurring elsewhere. Astonishingly, although these forests occupy only about 1% of the Earth’s land surface, they contribute over 8% of the total global CO2 emissions from fires. The implications are immense, with fires projected to increase greenhouse gas emissions from permafrost thaw by 30% by the end of this century. It is clear that the vulnerability of extratropical forests to climate change and lightning-induced wildfires places their carbon stores at great risk.
The timely importance of this research is evident in Canada’s recent devastating fire season in 2023, where fire emissions were more than four times higher than the previous average from 2003 to 2022. Preliminary reports indicate that widespread lightning ignitions were responsible for a significant portion of this year’s fires. Dr. Thomas Janssen from VU emphasizes that extreme fire seasons like Canada’s will become increasingly common in warmer climates due to hotter, drier weather and a higher prevalence of lightning strikes. The severity of recent fire seasons in the Siberian boreal forests in 2020 and 2021 further highlights the urgent need to address the escalating risks associated with climate change.
The emissions of greenhouse gases from wildfires exacerbate the issue of climate change, contributing to higher concentrations of carbon dioxide in the atmosphere. This, in turn, amplifies the likelihood of fires and other adverse impacts of climate change. Prof. Sander Veraverbeke of VU warns that this reinforcing feedback loop plays a crucial role in boreal forests, many of which are underlain by carbon-rich permafrost soils. Once lost to fire, these soils take centuries to form. Therefore, the impact of wildfires on greenhouse gas emissions has far-reaching consequences, making it imperative to tackle this issue urgently.
The research conducted by Dr. Matthew Jones and his team underscores the critical need for action to mitigate the risk of lightning-induced wildfires in boreal forests. As the planet continues to warm, each incremental increase in temperature translates directly into a higher risk of wildfires. Therefore, every effort to limit global warming by even a tenth of a degree significantly reduces this risk. Implementing sustainable land management practices, investing in fire prevention strategies, and reducing greenhouse gas emissions are paramount in safeguarding intact extratropical forests and the crucial carbon reserves they hold.
The escalating threat of lightning-induced wildfires in boreal forests presents a significant challenge. The dominance of lightning ignitions in these forests, coupled with the increasing frequency of lightning strikes and the vulnerability of carbon-rich ecosystems, necessitate immediate action. By understanding the critical role of climate change in exacerbating this issue, we can work towards effective strategies to protect our forests, mitigate greenhouse gas emissions, and ensure a sustainable future for our planet.