Fires in boreal forests release carbon records – 03/03/2023 – Environment

Fires in the boreal forests that surround the northernmost latitudes of the globe are emitting ever-increasing amounts of carbon dioxide (CO₂), according to an international study using new satellite technology.

The burning of boreal forests in Eurasia and North America in 2021 released a record 1.76 billion tonnes of CO₂—representing 23% of all global CO₂ emissions from fires. Global energy-related CO₂ emissions reached a record high of nearly 37 billion tonnes in the same year.

“Boreal forests can be a carbon ticking time bomb, and the recent increases in emissions from wildfires make me worry that time is running out,” said Steven Davis of the University of California at Irvine and co-author of the study, released at the annual meeting. of the American Association for the Advancement of Science in Washington and published in the journal Science.

The researchers, led by scientists at Tsinghua University in China, said that while rainforest fires have attracted much attention as a result of deforestation, boreal forests have been relatively neglected.

This occurred despite the fact that it is one of the most extensive and important biomes on Earth and is threatened by the warming that is occurring much faster in the Arctic region than in the rest of the planet.

Measuring emissions from fires is essential for modeling climate change. But it’s difficult to pinpoint the contribution of new carbon sources directly when the atmosphere already contains so much long-lived CO₂. Instead, the researchers resorted to an indirect method.

As a substitute, they monitored the carbon monoxide generated by fires, which only lasts a few weeks in the atmosphere before being oxidized to CO₂.

The analysis used data from an instrument on NASA’s Earth observation satellite, Mopitt (troposphere pollution measurements), which has a continuous series of records since 2000.

The results corroborate other evidence that fires have expanded over the last two decades in boreal forests, which consist mainly of conifers with some birch and poplar trees. Emissions from these fires increased rapidly in 2021, a year of severe drought and heat waves that continued into 2022, although data for the last year is not yet available.

Over the past ten years, wildfires in boreal regions have increased faster than in tropical forests, in part reflecting the fact that average temperatures are rising faster in the north of the planet than near the equator, as the reflective layer of snow and ice melts with global warming.

The research also confirms the feedback between climate change and wildfires.

Rising CO₂ emissions from fires “pose an increasing threat to the climate, as part of the emissions may not return to vegetation and soils”, say the scientists, “because trees do not grow as well in warmer conditions and dry”.

While the new study used satellite data, “we also need measurements on the ground to monitor wildfires,” said Philippe Ciais, co-author at the University of Paris-Saclay.

But the rupture of scientific relations with Russia – owner of the largest boreal area in the world – after the invasion of Ukraine “is a real problem for our understanding”, said Ciais. “We are going to lose several years before we officially get the data we need for the boreal regions of Russia and Siberia.”

_{Translated by Luiz Roberto M. Gonçalves}