Lightning kills 320 million trees each year

Most people don’t often witness the dramatic results of trees struck by lightning  firsthand—a fact that may lead you to believe thunderstorms don’t present too large a threat to our shade-providing friends. But according to the designers of a new statistical modelling program, the optimistic assumption is dead wrong. If anything, lightning is an even bigger tree-killer than previously believed.

According to calculations published in the journal Global Change Biology by a research team at Germany’s Technical University of Munich (TUM), lightning is liable to destroy around 320 million trees every year. These don’t include losses from lightning-ignited wildfires, either; the number strictly pertains to individual tree deaths.

Most lightning never actually makes it to Earth. Instead, the electrical discharges more often crackle within the clouds themselves. But as any thunderstorm watcher knows, quite a few lightning bolts still form when negative atmospheric charges merge with positively charged air columns rising up from the ground. Often, those air columns ascend from tall objects like buildings, radio towers—and, of course, trees.

Previous studies of lightning’s relationship with trees are largely limited to field observations from individual forests, so TUM’s atmospheric scientists opted to approach it from a different angle. The team combined a popular global vegetation model with datasets of global lightning patterns and observational data. They then ran mathematical calculations to get a sense of the annual tally of lightning tree strikes.

Based on their novel climate model, lightning manages to fatally injure 320 million trees per year—somewhere between 2.1 and 2.9 percent of annual plant biomass loss. But that’s not all they assessed.

“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, study lead author and TUM atmospheric scientist said in a statement.

Krause’s team believes the biomass decay from lightning-struck trees emits 0.77–1.09 billion tons of carbon dioxide every year, a much higher range than past figures. In ecology, biomass generally refers to the total amount of organic matter in an ecosystem. The number even approaches the roughly 1.26 billion tons of carbon dioxide annually released by plantlife during wildfires. That said, wildfires still eclipse the lightning statistic by a wide margin—around 5.85 billion tons every year, including deadwood and organic soil material.

The researchers believe their conclusions highlight the importance of factoring tree deaths from lightning into climatology studies. Unfortunately, it’s all the more pressing given that the sum will likely increase in the near-future.

“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.

 

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