For the first time, scientists managed to observe and measure weak electrical discharges, known as coronas, in trees during thunderstorms. The discovery was recorded on the east coast of the United States during the summer of 2024.
These discharges generate almost imperceptible flashes, similar to a faint blue glow that manifests at the tips of the leaves. Although the human eye cannot detect them in natural conditions, instruments confirmed their repeated presence in different species.
The study was published in Geophysical Research Letters, a journal of the American Geophysical Union dedicated to relevant advances in geosciences. Thus, a hypothesis proposed for almost a century obtained empirical support in open field.
How are coronas produced in the treetops?
The phenomenon occurs when the electric charge of a storm induces an opposite charge in the ground. Consequently, that energy rises to the highest available points, such as the leaves in the treetops.
Concentrating at the tips, the electricity is released in the form of small discharges that emit ultraviolet radiation. In the laboratory, these coronas are perceived as a faint bluish glow when external light sources are removed.
Additionally, previous experiments showed that the UV radiation emitted is proportionally related to the electric current passing through the tree. Therefore, these emissions could serve as an indirect indicator of electrical stress in the forest canopy.
A minivan converted into a mobile laboratory
To document the phenomenon in real conditions, the team adapted a 2013 Toyota Sienna with scientific instruments. The vehicle incorporated a weather station, electric field detectors, and a camera sensitive to ultraviolet radiation.
The observations included records in Pembroke, North Carolina, and storm tracking between Florida and Pennsylvania. During 90 minutes under a storm, 41 coronas on sweetgum branches were detected, with flashes lasting up to three seconds.
The behavior was similar in a nearby loblolly pine and other observed species. Therefore, researchers estimate that dozens or even hundreds of leaves per tree could emit flashes simultaneously during intense storms.
Ecological impacts and possible consequences in the canopy
Coronas not only emit ultraviolet light but can also burn the tips of the leaves in a matter of seconds. Previous studies suggest that the electric current can damage cell membranes and chloroplasts, affecting photosynthesis.
Furthermore, there is the possibility that the repetition of the phenomenon deteriorates the cuticle, the waxy layer that protects leaves from radiation and dehydration. Although a single discharge seems to cause limited damage, recurrence over multiple storms could generate cumulative effects.
Consequently, scientists suggest that this process could have influenced the evolution of certain characteristics of the forest canopy. Understanding these interactions will allow for the evaluation of how forests respond to electrical events in the context of potentially more intense storms due to climate change.
