New critique debunks claim that trees can sense a solar eclipse

Last year, a group of scientists shared evidence suggesting that spruce trees in Italy's Dolomite mountains synchronized their electrical activity before a partial solar eclipse. This discovery seemed to offer a new look into how plants communicate and understand the world around them. The findings quickly caught the attention of news organizations and even led to the creation of a documentary. However, many other researchers in the field reacted with sharp criticism. Some questioned whether the original study should have been published at all. Now, a new report published in the journal Trends in Plant Science outlines these concerns in great detail.

For the original study, Alessandro Chiolerio, a physicist, worked with plant ecologist Monica Gagliano and others. They set up an experiment in the Costa Bocche forest located in the Dolomites. The team essentially created an electrocardiogram, or EKG, for trees. They attached electrodes to three spruce trees, which were between 20 and 70 years old, and to five tree stumps. These sensors recorded a significant increase in bioelectrical activity during a partial solar eclipse on October 22, 2022. The activity reached its highest point during the middle of the eclipse and then faded away afterward. The authors interpreted this spike as a coordinated response from the trees to the darkened sky.

The electrical activity of the older trees spiked earlier and more strongly than the activity of younger trees. The researchers felt this suggested that trees have a kind of memory regarding such events. They believed older trees might even transmit this knowledge to younger trees. This idea was based on their detection of bioelectrical waves traveling between the trees. Soon, other plant scientists weighed in with strong skepticism. They cited the study's small sample size and the large number of variables that could not be controlled.

Justine Karst, a forest ecologist at the University of Alberta in Canada, compared the findings to a controversial 2019 study about the "wood-wide web." This concept suggests that trees share resources and communicate through underground fungal networks. Karst co-authored a 2023 study that showed there was not enough evidence to support the wood-wide web theory.

Ariel Novoplansky, an evolutionary ecologist at Ben-Gurion University in Israel, was one of the first to object to the study's publication. He later co-authored the new critique with his colleague Hezi Yizhaq. Novoplansky believes the spikes in electrical activity were much more likely caused by temperature shifts or nearby lightning strikes. He told the news outlet Ars that his doubts arose from the basic premise of the study. The entire argument relied on the idea that trees would be functionally affected by the minor effects of a partial eclipse. This eclipse only reduced sunlight by 10.5 percent for two hours. Novoplansky noted that thunderstorms might be involved in the heightened electrical activity.

According to Novoplansky, forest trees experience far greater fluctuations in cloud cover and light quality every day than they did during the partial eclipse. He also objected to the idea that older trees could share "knowledge" of an eclipse with younger ones. He pointed out that every solar eclipse follows a unique path across the sky. Even if older trees remembered a past eclipse, they could not use that memory to anticipate a future one. The gravitational changes associated with a partial eclipse are minor. They are on par with the gravity of a new moon. For these reasons, Novoplansky stated that the 2025 paper represents the encroachment of pseudoscience into the heart of biological research.