Without strong climate action, forests on every continent will be highly flammable for at least 30 extra days per year by the end of the century, and this fire threat is much greater for some forests.
Our research in Nature Communications looked at 20 years of global satellite data to test the link between wildfires and vapor pressure deficit, a measure of the atmosphere's power to suck water out of plants. The air can be thought of as tacky.
The results show that forest fire is more likely to occur above a certain threshold. The threshold is dependent on the forest.
Climate change is increasing the number of days on the planet. We can reduce the number of extra wildfire days if we bring global emissions down.
The phenomenon of wildfire is very old. There are four important conditions for a fire.
Four processes are switches. All have to be in the right place at the right time for a fire to start.
The drying out of fuel is necessary to make a forest dangerous. There are links between fire activity and the Vapor Pressure Deficit.
VPD shows the difference between how much water is in the air and how much water is in the air when it's wet. Water condenses when air becomes saturated.
VPD is increased by warmer air holding more water. When the gap between full and empty air becomes bigger, there's a greater demand for the water to come out of living and dead plants.
Climate change will cause global temperatures to rise.
We looked at more than 30 million satellite records and a global climate dataset to find the maximum daily VPD.
The strength of the relationship between VPD and fire activity was measured. We showed for the first time that there is a strong correlation between fire activity and VPD in many forests.
We found VPD thresholds beyond which forest fire becomes more likely than not.
The threshold is a unit of pressure in the forest. The threshold in the Amazon is between 1.5 and 3.0 kilopascals. In the tropical forests of Borneo and Sumatra, the air must be a lot more thirsty to ignite fire.
If we don't curb emissions, the risks are much higher.
The planet is expected to warm by around 3.7 C by the end of the century if humanity continues to emit greenhouse gases. There are forests on every continent that will experience at least 30 extra days per year above critical flammability thresholds.
Each continent will see at least an extra 15 days per year crossing the threshold under a lower emissions scenario.
There will be at least 90 additional days in a low-emissions scenario and at least 150 additional days in a high-emissions scenario in parts of tropical South America.
There will be consequences if forest fires increase. Potentially destabilizing patterns of fire and regrowth are included. According to research done last year, the role of the Amazon rainforest as a carbon sink may be in decline.
Increasing harms to human health can be expected from the smoke. More than 300,000 people die every year from smoke inhalation. The most populated areas of South Asia and East Africa could see an increase in this number by the century's end.
The links between fire, VPD, and climate change will be explored in more detail in Australia. VPD doesn't seem to be the main driver of fire in Japan and other areas.
Better fire predictions can be made at both seasonal and near-term scales thanks to our discovery of reliable links between atmospheric dryness and forest fire risk. Those on the front lines of fighting, managing, and coexisting with wildfire could benefit from this.
The contributions of Shiva Khanal were acknowledged by the authors.
The University of Melbourne has a senior research fellow, a professor and a post-doc.
Under a Creative Commons license, this article is re-posted. The original article is worth a read.
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