Researchers are testing whether increasing UV radiation is altering chemistry of tree leaves, increasing the likelihood and severity of wildfires
By Madeleine Cuff
12 August 2025
A flammability test on a western juniper tree
Rebecca Koll
Tucked away in a laboratory at the University of Exeter in the UK, Rebecca Koll is setting conifer trees alight in the hope of answering burning questions about the future of forest fires.
Wildfires are increasing in severity around the world as the climate warms. This is largely driven by increasing heat, drought and wind speeds making trees more likely to burn when sparks fly.
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But Koll is among a group of researchers who suspect it isn’t just drought and other direct effects that are boosting the risk of fires. “Is climate change actually changing the plants themselves? We’re pretty sure it is,” she says.
She believes the leaf chemistry of trees is being altered by climate stressors such as increasing ultraviolet radiation, which makes plants produce more airborne chemicals – known as volatiles – in a type of stress response.
Studies have shown that exposing some food and medicinal crops to higher levels of UVB triggers an increase in volatile compounds in their leaves. Separate analysis indicates that high levels of volatiles in conifers, such as pine trees, increase their flammability.