When we get a whiff of a bad smell or detect the presence of toxic substances, one of our first reflexes is to cover our nose and mouth. Now, US researchers suggest that forest trees adopt more or less the same survival instincts.
Scientists Delphine Farmer and MJ Riches were able to observe in real time the reaction of living pine leaves to smoke from forest fires, following a fire in 2020 at their research site in the Rocky Mountains of Colorado.
Their initial study was to investigate how pine trees emit volatile organic compounds; but when they carried out their usual sampling at leaf level, they found that the tree’s pores were completely closed and that photosynthesis was almost nonexistent – which, in practical terms, meant the plants weren’t breathing.
“Plants have pores on the surface of their leaves called stomata. These pores are much like our mouths, except where we inhale oxygen and exhale carbon dioxide, plants inhale carbon dioxide and exhale oxygen,” the authors explained in the journal The Conversation.
“What our months of data have taught us is that some plants react to heavy bouts of wildfire smoke by shutting down their exchange with outside air. They are effectively ‘holding their breath’, but not before they have been exposed to the smoke,” the scientists continued.
These plants were able to enhance photosynthesis and release volatile organic compounds from the leaves when temperature and humidity were restored.
“Most modern findings on the effects of wildfire smoke on crops have been conflicting,” the experts noted. “This lack of research is driven by the fact that studying smoke effects on the leaves of living plants in the wild is difficult: wildfires are hard to predict, and it can be unsafe to be in smoky conditions.”
They added that further research is required to better understand the risks and impacts of forest fires on tree health.
The frequency and intensity of forest fires has almost doubled in the space of 20 years, largely owing to climate change. A study published in 2022 by researchers from the University of Maryland showed that 26-29% of global forest loss between 2001 and 2019 would be due to such fires.
Indeed, hot seasons have been leading to more and more devastating fires in different parts of the world, such as those raging on the outskirts of Athens. Since Aug 11, the area around the Greek capital has been hit by some 40 fires of considerable intensity, spread over some 30km.
According to local experts, these forest fires are probably owing to the region’s prolonged drought, very high temperatures of up to 39°C, and powerful winds of over 90 km/h.