Some of the biggest areas of concern are the Amazon rainforest and other tropical forests, as well as northern hemisphere temperate and boreal forests.
A new study led by Australian researchers has found that greater atmospheric demand for water is associated with a rising risk of major fires in global forests, calling for more urgent and effective action to combat climate change.
Published in the Nature Communications journal, the study examined satellite records of fire activity and a global climate dataset to find the maximum daily vapor pressure deficit (VPD) for every fire detection -- over 30 million records in the last 20 years.
As a measure of the atmosphere's thirst, VPD describes the difference between how much moisture is in the air, and how much moisture the air can hold when it's saturated. The greater this difference, the greater the air's drying power on fuels.
A forest fire is much more likely above a certain threshold in VPD, while the thresholds differ between forest types, being lower in boreal and temperate forests and higher in Mediterranean, subtropical and tropical forests.
Using VPD as a parameter, the research team predicted that climate change can lead to widespread increases in forest risk, with at least 30 additional days above critical thresholds for fire activity in forest biomes on every continent by 2100.
Hamish Clarke, research lead from the University of Melbourne, said that all around the world, there are more conditions under which forests dry out and become flammable.
"Some of the biggest areas of concern are the Amazon rainforest and other tropical forests, as well as northern hemisphere temperate and boreal forests. Without strong climate action, there will be many more days each year - at least 30 - when Earth's forests cross over into this critical flammability zone. This means we're likely to see more major fires, with all the risks that come with them," Clarke said.
The study also warned that escalating forest fire risk threatens major population centers in Africa and Asia, as increased wildfire smoke has substantial impacts on human health.
"It is currently estimated that over 330,000 annual deaths globally are attributable to smoke inhalation, a number that could increase notably by the turn of the century, particularly in the most populated areas of east Asia," Clarke added.