The researchers said that climate change was likely a “major driver” in increased fire activity, with extreme heat waves that render forests tinder dry already five times more likely today than a century and a half ago.
These drier conditions lead to higher emissions from fires, further exacerbating climate change as part of a “fire-climate feedback loop”, they said.
The vast majority – about 70 per cent – of fire-related tree cover loss over the last two decades occurred in boreal regions, likely because high-latitude regions are warming at a faster rate than the rest of the planet.
Last year, Russia lost 5.4 million hectares of tree cover due to fires, the highest on record at an increase of 31 per cent over 2020.
“This record-breaking loss was due in part to prolonged heatwaves that would have been practically impossible without human-induced climate change,” said the study.
The team warned that increased changes to climate and fire activity could eventually turn boreal forests from a carbon sink into a source for carbon emissions.
“In these boreal regions carbon has accumulated in the soil over hundreds of years and has been protected by a moist layer on top,” said McCarthy.
“These more frequent and serious fires are burning off this top layer and it’s exposing that carbon in the soil.”
This century, fire-related tree cover loss in the tropics has increased around 5 per cent – about 36,000 hectares – a year, the study showed.
Fire is not the principal cause of forest loss in these regions, with deforestation and forest degradation the main drivers.
But the researchers said that forest loss from deforestation was making it more likely that forests would be lost to fire, as the practice leads to higher regional temperatures and drier vegetation.
They called on governments to improve forest resilience by ending deforestation and limiting local forest management practices that include controlled burning, which can easily burn out of control particularly during dry spells.
“Forests are one of the best defences we have against climate change,” said McCarthy.