We’ve all seen dramatic footage of lightning striking a mighty tree, its branches going up in flames. But how often does this actually happen? Researchers didn’t know how much lightning impacted forests—until now.
Researchers at the Technical University of Munich (TUM) have developed a computer model to provide what they claim to be the first estimate of lightning’s impact on forest ecosystems around the world. According to their study, lightning affects forests more than previously thought. Specifically, they suggest that around 320 million trees die each year from lightning strikes, not including the trees that die in lightning-induced wildfires.
“Lightning is an important yet often overlooked disturbance agent in forest ecosystems,” the researchers explained in the study, published last month in the journal Global Change Biology.
To make their estimate, they integrated observational data and global lightning patterns into a well-known global vegetation simulation. The computer model indicates that trees killed by lightning represent 2.1% to 2.9% of all plant biomass loss annually. While plants and trees absorb CO2 through photosynthesis during their lifetimes, they release a significant amount of it back into the atmosphere when they die and decay. As such, these figures are crucial to better understanding Earth’s carbon cycling.
With the combined model, “we’re now able not only to estimate how many trees die from lightning strikes annually, but also to identify the regions most affected and assess the implications for global carbon storage and forest structure,” Andreas Krause, lead author of the study and researcher at the Chair of Land Surface-Atmosphere Interactions, explained in a TUM statement.
The biomass decay caused by the lightning-killed trees is estimated to emit between 770 million and 1.09 billion tons of carbon dioxide annually. According to the researchers, this is surprisingly high. For comparison, living plants burned in wildfires release around 1.26 billion tons of CO2 every year. Both of these figures, however, are dwarfed by the total wildfires CO2 emissions (including the combustion of deadwood and soil material), which is approximately 5.85 billion tons per year.
“Most climate models project an increase in lightning frequency in the coming decades, so it’s worth paying closer attention to this largely overlooked disturbance,” said Krause. “Currently, lightning-induced tree mortality is highest in tropical regions. However, models suggest that lightning frequency will increase primarily in middle- and high-latitude regions, meaning that lightning mortality could also become more relevant in temperate and boreal forests.”
The researchers argue that ecosystem models need to account for lightning mortality in order to better predict vegetation dynamics. Interestingly, though, not all trees die after getting struck by lightning—in fact, some kinda like it.