Trees sync up their communication signals before a solar eclipse

High in the Dolomites of northern Italy, a quiet forest of spruce trees witnessed a cosmic event. As the moon began its slow passage across the face of the sun, these trees did something extraordinary. They didn’t just react to the solar eclipse – they prepared for it.

Hours before the eclipse unfolded, the inner signals of the trees began to shift in synchrony, echoing across the forest like an invisible wave.

What if forests could think? What if they didn’t just survive but sensed, remembered, and collectively adapted? These questions are no longer the domain of poetic speculation. A new international study has brought scientific weight to these ideas, revealing a forest’s capacity for anticipation and communication.

Led by Professor Alessandro Chiolerio of the Italian Institute of Technology (IIT) and the University of the West of England (UWE), and Professor Monica Gagliano of Southern Cross University, the research shows how spruce trees behave not just as individuals but as members of a responsive, interconnected ecosystem.

The trees began altering their bioelectrical rhythms well before the eclipse. This wasn’t passive reaction – it was a coordinated prelude.

Older trees sense eclipse first

The researchers placed specialized sensors on trees ranging from decades-old elders to young saplings. The trees’ bioelectrical signals – minute voltage changes across their tissues – began shifting as early as 14 hours before the solar eclipse occurred.

Remarkably, older trees were the first to display these changes. They exhibited increased entropy and bioelectrical complexity long before the event, suggesting deep memory rooted in past experiences.

These ancient trees acted as environmental archives, holding clues from previous eclipses and perhaps other rare events that have repeated over their long lives.

“The fact that older trees respond first – potentially guiding the collective response of the forest – speaks volumes about their role as memory banks of past environmental events,” said Professor Gagliano.

This age-based hierarchy of response shows that trees are not just passive organisms. Instead, they may actively use memory to shape real-time responses to future events. The old trees don’t simply endure – they teach.

Tree signals sync before an eclipse

Custom-built CyberTree sensors recorded data from trees at four distinct forest sites. Trees of different ages and light exposure were included. Some trees were healthy and tall, others young and shaded, and several were even stumps from felled trees.

In one 20-year-old tree, researchers noticed sharp, square-wave-like bioelectrical spikes hours before the eclipse. These signals vanished immediately after the event, creating a clear boundary in the data.

Older trees showed broader but more persistent fluctuations. During the eclipse itself, bioelectrical activity became less chaotic and more ordered.

“This study illustrates the anticipatory and synchronized responses we observed are key to understanding how forests communicate and adapt, revealing a new layer of complexity in plant behavior,” explained Professor Gagliano.

This coordination wasn’t superficial. It ran deep through the trees’ vascular systems – through xylem and phloem – recorded using electrodes both within trunks and around their circumference. The result was a living, electrical map of the forest’s inner state.

Whole forest acts as one system

The synchrony wasn’t limited to isolated trees. Researchers applied cross-correlation analysis to examine relationships among signals from different trees. What they found was striking. As the eclipse approached, trees didn’t just change individually. They aligned with each other.

Compared to normal days, during the eclipse the trees exhibited larger deviations in signal symmetry. This meant the forest wasn’t operating randomly. Each tree’s electrical behavior influenced – and was influenced by – others. These shifts showed signs of communication and responsiveness beyond traditional ecological models.

“We now see the forest not as a mere collection of individuals, but as an orchestra of phase correlated plants,” said Professor Chiolerio.

Especially strong synchrony occurred between the oldest trees, suggesting that longevity also brings a central role in networked behaviors. Their signals moved together like synchronized swimmers, responding as one to the cosmic shift overhead.

How trees align their behavior

To make sense of this synchrony, the team turned to an unlikely ally – quantum field theory (QFT). Trees, they argued, are open, dissipative systems. They constantly exchange energy with their environment, and classical physics falls short in describing their complex coordination.

By using thermal QFT models, the researchers could describe the trees’ behavior at both molecular and systemic levels. They showed how microscopic structures like ion channels and water molecules aligned their activity, giving rise to coherent macroscopic behavior.

In this framework, the forest’s response becomes a form of spontaneous symmetry breaking. That is, a small environmental trigger – in this case, the eclipse – produces a large-scale shift in system organization.

During the eclipse, the system’s entropy dropped, coherence increased, and the forest appeared to enter a new state – like an orchestra locking into tempo after tuning their instruments. The forest was not only alive. It was aware.

Gravity may cue the response

A mystery remained: how could trees begin responding before the eclipse even started? The usual suspects – light, temperature, and humidity – couldn’t explain it. Trees began shifting their signals when it was still daylight and warm, and the Moon was far from their sky.

The authors propose another trigger: gravimetric tides. These are subtle shifts in Earth’s gravitational field caused by the alignment of the Moon and Sun. During a solar eclipse, especially one aligned with a Saros cycle, these tides peak.

Such gravimetric cues are hard for humans to detect, but not for trees. Their deep-rooted structure and fluid dynamics make them excellent sensors. Older trees, which have lived through several Saros cycles, may recognize this pattern and respond early.

“This discovery underscores the critical importance of protecting older forests, which serve as pillars of ecosystem resilience by preserving and transmitting invaluable ecological knowledge,” said Professor Gagliano.

Implications for conservation science

This research expands our understanding of what a forest is. No longer can we see it as a collection of competing individuals. The trees synchronize their internal processes, align responses to stimuli, and likely share information across time and space.

This makes old-growth forests irreplaceable. Logging them erases not just biomass, but knowledge – decades or centuries of stored information that newer trees have not yet acquired.

From the lens of ecological stability, these forests act like community elders. They modulate, anticipate, and respond, ensuring the forest survives sudden changes. Protecting them becomes not only an act of conservation, but an act of safeguarding planetary memory.

The hidden intelligence of forests

To share this finding with a wider audience, the research team collaborated on a documentary. Il Codice del Bosco (The Forest Code) is scheduled for release in Italy in May 2025. It brings the forest’s hidden world to life, showing trees as responsive and intelligent beings.

“Basically, we are watching the famous ‘wood wide web’ in action!” said Professor Gagliano.

The documentary will visualize the forest’s electrical signals, offering viewers a glimpse into a world usually invisible. It represents a step toward redefining how we relate to nature – not as masters, but as fellow participants.

Trees remember eclipses and adapt

The study of spruce trees during a solar eclipse has revealed something profound. Trees do not simply endure. They anticipate, adapt, and align with each other through non-verbal, bioelectrical communication. They exhibit behaviors long thought reserved for animals – coordination, memory, and possibly a form of decision-making.

As we understand this hidden intelligence, our approach to ecology must evolve. Forests are not just lungs of the planet. They are its silent minds – thinking slowly, speaking in signals, and remembering events we cannot see.

The study is published in the journal Royal Society Open Science.

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