Drought stress, rising carbon dioxide, global heating and wildfires are widely recognised as major causes of tree death in tropical forests. But a new study points to a lesser-known culprit: The growing frequency of thunderstorms, now emerging as a significant driver of forest mortality.
Based on historical trends, these convective storms may account for up to 50 per cent of the reported rise in biomass mortality across the Amazon, stated the study published in the journal Ecology Letters on July 1, 2025. Depending on the assumptions used, the impact could range anywhere from 12 per cent and go up to as high as 118 per cent.
Convective storms, which are small-scale weather events covering tens to hundreds of square kilometres, are characterised by vertical atmospheric instability, strong winds and lightning. Unlike hurricanes, typhoons or cyclones, they are short-lived and localised, but, as the study finds, disproportionately lethal for forests.
Despite their scale, these events contribute significantly to biomass loss. The paper noted that wind and lightning together are responsible for a substantial share of pantropical tree mortality.
The team was surprised to find that storms may be the largest single factor causing tree death in these forests, said lead author of the study Evan Gora in a statement released by Cary Institute of Ecosystem Studies. “They’re largely overlooked by research into carbon storage in the tropics. Our estimates suggest that storms are responsible for 30-60 per cent of tree mortality in the past, and that number must be increasing as storm activity increases by 5-25 per cent each decade,” he added.
Storms typically break or uproot trees, damaging not only the trees themselves but also others they fall upon. Forest inventory data from the Amazon suggest that 51 per cent of all trees die from being broken or uprooted, likely due in large part to high winds, the study noted.
Lightning also plays a deadly role. A single strike can damage around 24 trees and kill five, even without causing fire or explosions. The study estimated that 35-67 million lightning strikes hit tropical forests annually, killing billions of trees in the process.
Even conservative estimates suggested storms are responsible for 30-60 per cent of biomass mortality across tropical forests.
Yet, the authors argued, storms remain under-researched as a driver of tree death. Drawing on previous studies on carbon stocks, they concluded that storms are as destructive as droughts and heat stress in terms of mortality patterns and their impact on the forest carbon sink.
Moreover, with thunderstorm activity rising by 5-25 per cent per decade over the past 50 years, the researchers warned that climate change is likely to worsen the situation. More frequent storms in tropical forests may be a major reason for the rise in tree deaths, which is weakening the forests’ ability to absorb carbon, the researchers observed.