A new study says the decline in global burned area from wildfires during the 20th century due to land-use change was almost completely offset by an increase caused by global warming.
The paper, published in the journal Nature Native local weather Change, is the first attribution study to assess the impacts of climate change and land-use change on “the global burned area.”
It found that changes in population distribution and land use during the 20th century – including forest fragmentation and land conversion for urban development and agriculture – suppressed wildfires, reducing the area burned globally by 19%.
However, this decline has been hampered by human-caused warming, which has increased the area burned by 16% due to increasingly hot and dry conditions around the world.
As a result, global burned area has decreased by only 5% over the past 100 years.
Despite the overall decline worldwide, the study found that climate change has caused the number of areas burned to increase by 29% in southeastern South America, 22% in northern Australia, 18% in western Siberia and 15% in western North America.
The study is “a crucial missing piece in the puzzle of tracking human-made emissions,” said Dr Matthew Jones, an independent researcher not involved in the study.
Jones, who works on the annual Global Carbon Budget (GCB), told Carbon Momentary that the study is a “major step forward in modeling the extent of additional human-caused fires.” He noted that to date, projects like the GCB “have been forced to assume that all emissions from wildfires are natural, thus underestimating the human impact on the global carbon cycle.”
Fire zone paradox
Australia’s 2020-21 “black summer” bushfires were one of the most intense and costly fire seasons on record on the continent. The fires burned nearly 25 million hectares of land, killed more than 30 people and released more CO2 than the annual emissions of more than 100 countries combined.
Researchers from the World Native Climate Attribution (WWA) service have released a “rapid attribution” study of Australian bushfires, finding that the likelihood of Australia experiencing weather conditions similar to those that led to the 2020-21 bushfires has increased by at least 30% since 1900 due to climate change.
Similarly, WWA found that climate change more than doubled the likelihood of extreme weather conditions leading to unprecedented wildfires in eastern Canada in 2023. And the hot, dry, and windy conditions that fueled devastating wildfires in the Pantanal in 2024 were 40% more intense due to climate change.
Attribution studies clearly show that climate change is making individual wildfires more intense and more frequent. However, the data show that, overall, the area burned by fires globally is decreasing.
Dr Matthew Jones is an independent researcher with the Natural Environment Research Council and the Global Carbon Project. He was the lead author of a study published last week that found carbon emissions from wildfires had increased by 60% globally between 2001 and 2023.
Climate change doesn’t provide the whole picture when it comes to global fire areas, he told Carbon Momentary, noting that human activity can impact wildfires in a number of ways:
“Wildfires are a natural phenomenon, but they are becoming increasingly likely due to human-caused climate change, and they are also influenced by humans, who manage much of the land area on Earth and also change the rate at which fires catch.
“Fire scientists have long struggled with the tricky task of separating out the additional fires that humans are causing, beyond those that would otherwise occur naturally.”
Burned area allocation
Seppe Lampe is a PhD student in the water and climate department at Vrije Universiteit Brussels and co-lead author of the study. He told Carbon Momentary that “this is the first study to really identify and quantify how climate change has affected burned areas around the world.”
The authors used seven “fire vegetation models” from the Intercomparison Impact Modeling Project to conduct an attribution study, comparing wildfires in today’s climate with wildfires in a counterfactual world without human-caused climate change.
To assess the impact of climate change on global burned areas, the authors ran current-day climate models (2003-2019) both with and without climate change impacts. They then compared the results to isolate the impact of climate change on global burned areas.
To study the impact of “direct human forcing”—defined as changes in land use, land management, and population density—they compared simulations of the world in the early industrial era (1901–17) and the world today (2003–19) without climate change. In these simulations, the authors did not include any long-term changes in climate, so the only differences were in land use and population changes.
The maps below show the percentage change in burned area due to climate change (top), direct human forcing (middle), and both (bottom). Red indicates an increase in the percentage of burned area, and blue indicates a decrease. White indicates that there has been little change in the percentage of burned area. The map divides the world into hexagonal regions, which are used by the Intergovernmental Panel on Climate Change (IPCC).
Climate change and land use
The study found that climate change has increased burned area in most IPCC regions, with only eight of the 42 regions experiencing a decrease in burned area due to climate change.
Lamp explained that climate-related reductions in burned area in regions like Southeast Asia could be due to factors like changes in rainfall patterns.
Many regions have seen more than a 10% increase in burned area due to climate change alone, the study added, including all IPCC regions in Australia and parts of South America, Siberia and North America.
The authors found that on average, climate change has increased global burned area by 16% and increased the likelihood of experiencing months with above-average global burned area by 22%.
The authors add that the area of land that would burn during the two most intense wildfire months of the year in a world without climate change is now expected to burn for four months each year.
The authors also found that the impact of climate change on fire-affected areas is increasing over time, with the fastest increase after the 1970s. Central Australia has seen the largest increase.
In contrast, the authors found that changes in direct human forcing factors since the early industrial period have resulted in a 19.1% reduction in burned area.
This is due to landscape fragmentation, reduced fire fuels — often seen when landscapes are converted from natural areas to urban areas or cropland — and intentional fire suppression and management techniques, the study found.
The decrease in burned area is mainly seen in savannas, grasslands and croplands – particularly in equatorial Asia and tropical North Africa – Lamp told Carbon Momentary. He added:
“The global signal of burned area is actually 70% determined by what’s happening in the African savannas. And there we’re seeing more and more savannas being converted to cropland, which is reducing the area that’s burned.”
Overall, the study found that global burned area has decreased by 5% since the beginning of the 20th century.
‘Big step forward’
The study found that without the “mitigating effects” of land-use change, the global burned area today would be even higher.
Jones told Carbon Momentary that the work was a “major step forward in modelling the extent of human-induced fires”. He added:
“To date, projects such as the Global Carbon Budget have struggled to estimate the extent to which humans are influencing climate through wildfire emissions. We are forced to assume that all wildfire emissions are natural, thus underestimating the human impact on the global carbon cycle.”
The study is “a crucial missing piece in the puzzle of tracking human-made emissions,” he explained.
Professor David Bowman, an Australian Research Council Laureate Fellow and director of the Interdisciplinary Fire Centre at the University of Tasmania, told Carbon Momentary that the approach used in the study appeared “valid”, but added that bushfire modelling was “extremely difficult”.
He points out some important assumptions and caveats in the “useful” study — for example, the authors did not consider the intensity of the fires.
Bowman also warned that the decline in global wildfire area “has been used for political purposes to deflect attention from the escalating wildfire crisis”.
Dr Maria Barbosa – a researcher at the Universidade Federal de São Carlos who was not involved in the study – told Carbon Momentary that the study “provides valuable insights into how fire regimes may change”.
Barbosa warned that “we are currently unprepared for the upcoming bushfire season” and said governments need to invest in early warning systems, improve land-use planning to reduce fire risk and strengthen forest management and restoration policies.
Lamp told Carbon Momentary that the study’s findings could help inform regional policymakers and could have “important implications for loss and damage.”