Between 2001 and 2023, the carbon emissions from wildfires increased by 60% globally. Fires in extratropical forests, located outside the tropics in temperate and boreal climates, such as Canada’s coniferous forests, had a greater impact on the increase in emissions than fires in tropical forests. This is the conclusion made by Brazilian, European, and American researchers following a study published in October in Science journal. Vegetation burning is one of the processes that releases greenhouse gases such as carbon dioxide (CO₂) into the atmosphere, causing an increase in global warming, the driving force behind climate change.
The team analyzed and grouped the planet’s forests into 12 areas called “pyromes,” a combination of the words fire—pyros, in Greek—and biome. The researchers sought to understand how forest fires in these regions respond to environmental, climatic, and human settlement pressures. Ranging from the taiga areas (coniferous forests) near the Arctic to the pine forests of southern Australia, the pyromes include all major forest zones on the planet, not just tropical ones like the Amazon.
According to the study, the overall increase in emissions from biomass burning in forested areas is due to changes in the extent of fires, which are covering larger and larger areas. The increase in fire severity also had a significant impact. In 2023, carbon emissions per unit of burned area were 50% higher than in 2001.
The researchers were surprised to find a significant increase in CO₂ emissions from fires in the boreal forests of Eurasia and North America. The volume of carbon released into the atmosphere nearly tripled in these regions between 2001 and 2023.
“We did expect an increase, especially as these areas have been suffering more and more heatwaves and drought conditions, but not of this magnitude,” says Brazilian geographer and environmental scientist Thais Rosan, a postdoctoral fellow at the University of Exeter in the UK and coauthor of this study.
Among the causes of increased fire activity in forests at higher latitudes, the article highlights the frequent occurrence of dry weather as a result of climate change, low soil moisture, and higher vegetation growth rates. Under these conditions, plants begin to produce more biomass in their leaves and stems, providing material that can be burned.
The increase in emissions in boreal forests does not mean that tropical forests are in a comfortable position. Although carbon emissions from forest fires have decreased in regions such as the Amazon and Congo Basin in Africa over the period studied, fires also pose a threat to forests in warm climates. In the tropics, according to the study, the main factors driving fires are increasing population density, the development of roads and changes in land use to create new agricultural areas, and of course, climate change. It should be noted that the study does not include data from this year, which saw a sharp increase in fires in South American biomes such as the Amazon and the Pantanal.
To arrive at the findings published in the new article, the research team first used an algorithm to analyze remote sensing data from 414 of the planet’s forest ecoregions. “Within these ecoregions, we considered a series of variables, such as road and population density, burned area, and climate data,” explains another coauthor of the article, remote sensing expert Guilherme Mataveli, a postdoctoral researcher at the National Institute for Space Research (INPE) with a grant from FAPESP.
The next step was to use an artificial intelligence tool to identify patterns in the variables in order to group ecoregions with similar characteristics and fire behavior. This is how the team found the 12 pyromes, says Mataveli, who worked on the study while at the University of East Anglia in the United Kingdom. There, he worked with climate scientist Matthew Jones, who led the study.
“The research is important because we talk a lot about emissions from deforestation, but little about those from fire,” says Celso H. L. Silva-Junior, a carbon cycle expert at the Amazon Environmental Research Institute (IPAM) who did not participate in the study. “We thought that extratropical forests did not contribute that much to greenhouse gas emissions. These new findings are a real surprise.”
According to Silva-Junior, the findings add more evidence to what science has been warning about for decades: human-induced climate change is making forests more vulnerable to fire. One problem feeds and is fed by the other. Climate change is fueling wildfires, and emissions from burning vegetation are adding to global warming. “The vast amount of carbon stored in forest biomass is released into the atmosphere when an area burns. Given the interconnectedness of the Earth’s systems, this can have a snowball effect,” warns the IPAM researcher.
The story above was published with the title “More fuel for global warming” in issue 345 of November/2024.
Project
The influence of land use and land cover on fine particulate matter (PM2.5µm) emissions from fire in Amazonia and Cerrado biomes integrating modelling and remote sensing (nº 19/25701-8); Grant Mechanism Postdoctoral Fellowship; Supervisor Luiz Eduardo Oliveira e Cruz de Aragão (Inpe); Beneficiary Guilherme Mataveli; Investment R$854.824,59.
Scientific article
JONES, M.W. et al. Global rise in forest fire emissions linked to climate change in the extratropics. Science. October 14, 2024.
