Climate Change Could Increase Tree Flammability

In a laboratory at the University of Exeter, UK, Rebecca Koll is examining conifer species to explore critical questions related to future forest fire dynamics.

Wildfire severity is on the rise globally as temperatures continue to increase. This is largely attributed to heightened heat, prolonged drought, and stronger winds, all of which elevate the risk of igniting timber when sparks occur.

Yet, Koll is among a team of researchers who believe that factors beyond drought are influencing fire risk. “Is climate change actually altering the properties of the plants? I’m quite certain it is,” she shares.

She posits that climate stress factors could be modifying leaf chemistry. With an increase in UV radiation, plants may produce more volatile compounds as a stress response.

Research indicates that some crops and medicinal plants experience heightened UVB exposure, which increases volatile compound levels on their foliage. Studies show elevated volatility in conifer species such as pines, thereby enhancing their flammability.

While global initiatives aimed at restoring the ozone layer may mitigate UV radiation risks, studies indicate that climate change, especially the uptick in hot, clear days in Northern and Eastern Europe, has resulted in rising ground-level UVB levels in recent years. Models predict that this may escalate later in the century.

Koll is currently engaged in a project examining changes in leaf chemistry and flammability by exposing 87 conifer species to elevated UVB levels. Using climate-controlled chambers with optimal temperature and moisture regimens, they simulate exposure levels tripled compared to current conditions. After 4 to 8 weeks, the trees undergo analysis and combustion tests to evaluate their flammability.

“It’s designed to be an ideal environment. These plants are in a very favorable climate, except we bombard them with radiation,” Koll explains. “We’re observing early signs of yellowing in areas that should remain green. Their biochemical reactions during various tests are altering the chemistry of their leaves,” she elaborates.

The pivotal question remains whether these biochemical shifts will lead to heightened flammability and if they elucidate the increasing intensity of forest fires. “We’re already elevating UV levels in our natural settings,” Koll notes. “This may imply that the risk extends beyond drought to include the direct impacts on plant biology.”

Uncovering these insights could provide scientists with a clearer understanding of wildfire risks in the predominantly coniferous regions of the Northern Hemisphere. “This is fundamentally what leads to severe home destruction,” Koll states. “The natural surroundings are becoming increasingly flammable.”

This project is among the initial experiments conducted at the University of Exeter’s Global Weather Simulator, a newly established facility dedicated to plant research that opened this year. The climate control chambers can recreate variations in wind, precipitation, heat, and atmospheric variables to analyze how plants and insects respond to rapid climatic shifts.

Matthew Robson of the University of Cumbria emphasizes that this research may confirm the significance of leaf compound changes in determining certain tree species’ flammability. “The relative impact of these climatic factors on volatile and combustible carbon-rich compounds has not been thoroughly explored, which makes the current research at Exeter particularly intriguing,” he states.