Lightning identified as the leading cause of wildfires in boreal forests, threatening carbon storage
Peer-Reviewed Publication
Lightning is the dominant cause of wildfire ignition in boreal forests – areas of global importance for carbon storage – and will increase in frequency with climate change, according to new research.
Dr Matthew Jones of the University of East Anglia’s (UEA) Tyndall Centre for Climate Change Research, is senior author of the paper, ‘Extratropical forests increasingly at risk of lightning fires’, which is published today in Nature Geoscience. The study was led by Vrije Universiteit (VU) Amsterdam in collaboration with researchers from the University of Leeds, Jiangsu Academy of Agricultural Sciences (China), and BeZero Carbon Ltd. (London).
The study used machine learning to predict the dominant source of wildfire ignitions – human or ‘natural’ lightning ignitions – in all world regions. Reference data from seven world regions were used to optimise the predictions from the algorithm. The researchers say it’s the first study to attribute fire ignition sources globally.
The study shows 77 per cent of the burned areas in intact extratropical forests are related to lightning ignitions, in stark contrast to fires in the tropics, which are mostly ignited by people. Intact extratropical forests are those in an almost pristine state, with small human populations and low levels of land use, and they are primarily found in the remote boreal forests of the northern hemisphere.
Climate models were also used to investigate how lightning frequency will change as the planet warms. Lightning frequency was found to increase by 11 to 31 per cent per degree of global warming over intact extratropical forests, meaning that climate change brings a risk of more wildfire ignitions.
Lightning fires are on average larger, more intense and more strictly constrained to remote areas and periods of extreme fuel dryness than anthropogenic fires.
The team’s earlier work has shown that episodes of fire-prone weather are also becoming more frequent and intense as the climate warms, meaning that forests are also becoming more flammable, more regularly. Synchronous increases in the flammability of forests and the frequency of lightning strikes are a worrying sign that intact extratropical forests will face an increasing threat of wildfire in future.
Extratropical forests are globally significant because they store vast quantities of carbon in vegetation and permafrost soils. Approximately 91 per cent of these forests in the northern hemisphere are underlain by permafrost. When fires occur in these regions, they emit large amounts of carbon dioxide (CO2) and other greenhouse gases compared to other regions.
Despite occupying only around 1 per cent of Earth’s land surface, fires in intact extratropical forests emit more than 8 per cent of the total CO2 emissions from fires globally.
It’s estimated that fires may amplify emissions of greenhouse gases from permafrost thaw by 30 per cent by the end of the century, following a moderate emissions scenario.
Dr Jones, a Research Fellow whose work focuses on the carbon cycle and climate change, said: “Extratropical forests are globally important because they lock up dense stores of carbon in vegetation and soils, helping to keep CO2 out of the atmosphere and moderate global warming.
“However, when fires occur in these regions, they emit more CO2 per unit area than virtually anywhere else on Earth.
“Our research highlights that extratropical forests are vulnerable to the combined effects of a warmer, drier climate and a heightened likelihood of ignitions by lightning strikes.
“Future increases in lightning ignitions threaten to destabilise vast carbon stores in extratropical forests, particularly as weather conditions become warmer, drier, and overall more fire-prone in these regions.”
The research is particularly timely given Canada’s record-breaking fire season in 2023, when fire emissions were more than four times greater than the 2003-2022 average. Preliminary reports have indicated widespread lightning ignitions in Canada this year.
VU’s Dr Thomas Janssen, lead author of the study, said: “While our research did not focus specifically on this year’s extreme fire season in Canada, it does help us to understand this year’s events. Extreme fire seasons in boreal forests, like the one we saw in Canada this year, will be more likely in warmer climates due to hotter, drier weather and more lighting strikes.
“The fires in Canada this year closely follow record-breaking fire seasons in the Siberian boreal forests in 2020 and 2021.”
The authors 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 future.
Prof Sander Veraverbeke of VU said: “Increased greenhouse gas emissions from wildfires reinforces the problem of climate change, with more fires occurring as the climate warms and more greenhouse gases being emitted by fires.
“This ‘reinforcing feedback’ is particularly important in boreal forests, most of which are underlain by carbon-rich permafrost soils that take many hundreds of years to form if they are lost to fire.”
Dr Jones said: “Our work has shown that the risk of lightning ignitions increases substantially as the planet warms, meaning that every tenth of a degree of warming that we can avoid will translate directly into a reduced risk of wildfire.
“Curbing emissions of greenhouse gases from fossil fuel use and land use change is critical to avoiding the worst additional risks of wildfire in many regions, but especially in the boreal forests where fires are so sensitive to warming.”
‘Extratropical forests increasingly at risk of lightning fires’ is published 9 November 2023 in Nature Geoscience.
Lightning is the dominant cause of wildfire ignition in boreal forests – areas of global importance for carbon storage – and will increase in frequency with climate change, according to new research.
Dr Matthew Jones of the University of East Anglia’s (UEA) Tyndall Centre for Climate Change Research, is senior author of the paper, ‘Extratropical forests increasingly at risk of lightning fires’, which is published today in Nature Geoscience. The study was led by Vrije Universiteit (VU) Amsterdam in collaboration with researchers from the University of Leeds, Jiangsu Academy of Agricultural Sciences (China), and BeZero Carbon Ltd. (London).
The study used machine learning to predict the dominant source of wildfire ignitions – human or ‘natural’ lightning ignitions – in all world regions. Reference data from seven world regions were used to optimise the predictions from the algorithm. The researchers say it’s the first study to attribute fire ignition sources globally.
The study shows 77 per cent of the burned areas in intact extratropical forests are related to lightning ignitions, in stark contrast to fires in the tropics, which are mostly ignited by people. Intact extratropical forests are those in an almost pristine state, with small human populations and low levels of land use, and they are primarily found in the remote boreal forests of the northern hemisphere.
Climate models were also used to investigate how lightning frequency will change as the planet warms. Lightning frequency was found to increase by 11 to 31 per cent per degree of global warming over intact extratropical forests, meaning that climate change brings a risk of more wildfire ignitions.
Lightning fires are on average larger, more intense and more strictly constrained to remote areas and periods of extreme fuel dryness than anthropogenic fires.
The team’s earlier work has shown that episodes of fire-prone weather are also becoming more frequent and intense as the climate warms, meaning that forests are also becoming more flammable, more regularly. Synchronous increases in the flammability of forests and the frequency of lightning strikes are a worrying sign that intact extratropical forests will face an increasing threat of wildfire in future.
Extratropical forests are globally significant because they store vast quantities of carbon in vegetation and permafrost soils. Approximately 91 per cent of these forests in the northern hemisphere are underlain by permafrost. When fires occur in these regions, they emit large amounts of carbon dioxide (CO2) and other greenhouse gases compared to other regions.
Despite occupying only around 1 per cent of Earth’s land surface, fires in intact extratropical forests emit more than 8 per cent of the total CO2 emissions from fires globally.
It’s estimated that fires may amplify emissions of greenhouse gases from permafrost thaw by 30 per cent by the end of the century, following a moderate emissions scenario.
Dr Jones, a Research Fellow whose work focuses on the carbon cycle and climate change, said: “Extratropical forests are globally important because they lock up dense stores of carbon in vegetation and soils, helping to keep CO2 out of the atmosphere and moderate global warming.
“However, when fires occur in these regions, they emit more CO2 per unit area than virtually anywhere else on Earth.
“Our research highlights that extratropical forests are vulnerable to the combined effects of a warmer, drier climate and a heightened likelihood of ignitions by lightning strikes.
“Future increases in lightning ignitions threaten to destabilise vast carbon stores in extratropical forests, particularly as weather conditions become warmer, drier, and overall more fire-prone in these regions.”
The research is particularly timely given Canada’s record-breaking fire season in 2023, when fire emissions were more than four times greater than the 2003-2022 average. Preliminary reports have indicated widespread lightning ignitions in Canada this year.
VU’s Dr Thomas Janssen, lead author of the study, said: “While our research did not focus specifically on this year’s extreme fire season in Canada, it does help us to understand this year’s events. Extreme fire seasons in boreal forests, like the one we saw in Canada this year, will be more likely in warmer climates due to hotter, drier weather and more lighting strikes.
“The fires in Canada this year closely follow record-breaking fire seasons in the Siberian boreal forests in 2020 and 2021.”
The authors 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 future.
Prof Sander Veraverbeke of VU said: “Increased greenhouse gas emissions from wildfires reinforces the problem of climate change, with more fires occurring as the climate warms and more greenhouse gases being emitted by fires.
“This ‘reinforcing feedback’ is particularly important in boreal forests, most of which are underlain by carbon-rich permafrost soils that take many hundreds of years to form if they are lost to fire.”
Dr Jones said: “Our work has shown that the risk of lightning ignitions increases substantially as the planet warms, meaning that every tenth of a degree of warming that we can avoid will translate directly into a reduced risk of wildfire.
“Curbing emissions of greenhouse gases from fossil fuel use and land use change is critical to avoiding the worst additional risks of wildfire in many regions, but especially in the boreal forests where fires are so sensitive to warming.”
‘Extratropical forests increasingly at risk of lightning fires’ is published 9 November 2023 in Nature Geoscience.
JOURNAL
Nature Geoscience
Nature Geoscience
METHOD OF RESEARCH
Computational simulation/modeling
Computational simulation/modeling
SUBJECT OF RESEARCH
Not applicable
Not applicable
ARTICLE TITLE
Extratropical forests increasingly at risk of lightning fires
Extratropical forests increasingly at risk of lightning fires
ARTICLE PUBLICATION DATE
9-Nov-2023
9-Nov-2023
Wildfire risk to US homes is rising, especially in western grasslands and shrublands
Drawing on 30 years of data, researchers show that the number of homes within wildfire perimeters in the U.S. has doubled since the 1990s. This increasing risk is driven by both an increase in wildfires and the expansion of new homes into wildfire-prone areas, especially in the wildland-urban interface. Wildfire risks to homes are increasing, particularly in the wildland-urban interface (WUI), where houses and wildland vegetation are in close proximity. Over the last 12 years, more than 55,000 homes in the U.S. have been lost to wildfires due to rapid increases in both the total area of land burned and the number of houses in the WUI. However, despite widespread concerns about wildfire risk, how wildfire extent and housing expansion in different types of vegetation and WUI contribute to increasing wildfire risk and home losses in the U.S. remain unknown. Volker Radeloff and colleagues evaluated 30 years of data on wildfire occurrence and WUI growth in the U.S., from 1990 to 2020. The authors found that the number of houses within wildfire perimeters has more than doubled since the 1990s due to both housing expansion (47%) and an increase in wildfire occurrence (57%). Most houses exposed to wildfires were located in the WUI. The number of homes in the WUI has grown substantially since the 1990s, increasing by 46%, from 30 million to 44 million. Moreover, the WUI at-large has also grown, increasing by 31% over the last three decades. Radeloff et al. note that even though their findings show that any growth in WUI also increases wildfire risk to houses, the continued growth of new construction in these areas suggests that wildfire occurrence is not discouraging development. “This 30-year time series of wildfire-prone development based on a consistent methodology is valuable for research and policy design,” writes Jason Boomhower in a related Policy Forum. “Understanding how and where the WUI is growing or shrinking is crucial for designing and evaluating policies. It also allows researchers to unpack topics such as the effects of a broader housing market slowdown on WUI growth, as Radeloff et al. do.”
JOURNAL
Science
ARTICLE TITLE
Increasing wildfire risk to houses in the United States, especially in grasslands and shrublands
ARTICLE PUBLICATION DATE
10-Nov-2023
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