Tree signalling and solar eclipses

‘A living collective’: study shows trees synchronise electrical signals during a solar eclipse

Zenit Arti Audiovisive

Monica Gagliano, Southern Cross University and Prudence Gibson, UNSW Sydney

Earth’s cycles of light and dark profoundly affect billions of organisms. Events such as solar eclipses are known to bring about marked shifts in animals, but do they have the same effect on plants?

During a solar eclipse in a forest in Italy’s Dolomites region, scientists seized the chance to explore that fascinating question.

The researchers were monitoring the bioelectrical impulses of spruce trees, when a solar eclipse passed over. They left their sensors running to record the trees’ response to the eclipse – and what they observed was astonishing.

The spruce trees not only responded to the solar eclipse – they actively anticipated it, by synchronising their bioelectrical signals hours in advance.

This forest-wide phenomenon, detailed today in the journal Royal Society Open Science, reveals a new layer of complexity in plant behaviour. It adds to emerging evidence that plants actively participate in their ecosystems.

Lead author Monica Gagliano discusses the research findings.

Do trees respond collectively?

The research was led by Professor Alessandro Chiolerio of the Italian Institute of Technology, and Professor Monica Gagliano from Australia’s Southern Cross University, who is the lead author on this article. It also involved a team of international scientists.

A solar eclipse occurs when the Moon passes between the Sun and Earth, fully or partially blocking the Sun’s light.

An eclipse can inspire awe and even social cohesion in humans. Other animals have been shown to gather and synchronise their movements during such an event.

But scientists know very little about how plants respond to solar eclipses. Some research suggests the rapid transitions from darkness to light during an eclipse can change plant behaviour. But this research focuses on the responses of individual plants.

The latest study set out to discover if trees respond to a solar eclipse together, as a living collective.

Alessandro Chiolerio and Monica Gagliano at the site of the study. Simone Cargnoni

What the research involved

Charged molecules travel through the cells of all living organisms, transmitting electrical signals as they go. Collectively, this electrical activity is known as the organism’s “electrome”.

The electrical activity is primarily driven by the movement of ions across cell membranes. It creates tiny currents that allow organisms, including humans, to coordinate their body and communicate.

The researchers wanted to investigate the electrical signals of spruce trees (Picea abies) during a partial solar eclipse on October 25, 2022. It took place in the Costa Bocche forest near Paneveggio in the Dolomites area, Italy.

The study took place in the Dolomites in northeast Italy. Monica Gagliano

The scientists set out to understand the trees’ electrical activity during the hour-long eclipse. They used custom-built sensors and wired them to three trees. Two were healthy trees about 70 years old, one in full sun and one in full shade. The third was a healthy tree about 20 years old, in full shade.

They also attached the sensors to five tree stumps – the remnants old trees, originally part of a pristine forest, but which were devastated by a storm several years earlier.

For each tree and stump, the researchers used five pairs of electrodes, placed in both the inner and outer layers of the tree, including on exposed roots, branches and trunks. The electrodes were connected to the sensors.

This set-up allowed the scientists to monitor the bioelectrical activity from multiple trees and stumps across four sites during the solar eclipse. They examined both individual tree responses, and bioelectrical signals between trees.

In particular, the scientists measured changes in the trees’ “bioelectrical potentials”. This term refers to the differences in voltage across cell membranes.

The scientists attached electrodes and sensors to the trees to monitor their electrical activity. Zenit Arti Audiovisive

What did they find?

The electrical activity of all three trees became significantly more synchronised around the eclipse - both before and during the one-hour event. These changes occur at a microscopic level, such as inside water and lymph molecules in the tree.

The two older trees in the study had a much more pronounced early response to the impending eclipse than the young tree. This suggests older trees may have developed mechanisms to anticipate and respond to such events, similar to their responses to seasonal changes.

Solar eclipses may seem rare from a human perspective, but they follow cycles which can occur well within the lifespan of long-lived trees. The scientists also detected bioelectrical waves travelling between the trees. This suggests older trees may transmit their ecological knowledge to younger trees.

Such a dynamic is consistent with studies showing long-distance signalling between plants can help them coordinate various physiological functions in response to environmental changes.

The two older spruce trees in the study had a much more pronounced early response to the impending eclipse than the young tree. Zenith Audiovisual Arts

The researchers also detected changes in the bioelectrical responses of the stumps during the eclipse, albeit less pronounced than in the standing trees. This suggests the stumps were still alive.

The research team then used computer modelling, and advanced analytical methods including quantum field theory, to test the findings of the physical experiment.

The results reinforced the experimental results. That is, not only did the eclipse influence the bioelectrical responses of individual trees, the activity was correlated. This suggests a cohesive, organism-like reaction at the forest scale.

The researchers also detected changes in the bioelectrical responses of the stumps during the eclipse. Zenit Arti Audiovisive

Understanding forest connections

These findings align with extensive prior research by others, highlighting the extent to which trees in forest ecosystems are connected.

These behaviours may ultimately influence the forest ecosystem’s resilience, biodiversity and overall function, by helping it cope with rapid and unpredictable changes.

The findings also underscore the importance of protecting older forests, which serve as pillars of ecosystem resilience – potentially preserving and transmitting invaluable ecological knowledge.

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This research is featured in a documentary, Il Codice del Bosco (The Forest Code), premiering in Italy on May 1, 2025.

The findings underscore the importance of protecting older forests. Pictured: the Dolomites region. Zenith Audiovisual Arts

Monica Gagliano, Research Associate Professor in Evolutionary Biology, Southern Cross University and Prudence Gibson, Lecturer and Researcher in Plant Humanities, UNSW Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Activity from the Earth's sun and impact on satellites

Right now, the Sun is far more active than predicted – and small satellites are paying the price

Kyle McMullan, Curtin University

Last week, three tiny Australian satellites from Curtin University’s Binar Space Program burned up in Earth’s atmosphere. That was always going to happen. In fact, Binar means “fireball” in the Noongar language of the First Nations people of Perth.

When a satellite is in low Earth orbit (2,000km or less), it experiences orbital decay as it drags closer and closer to the surface, eventually burning up.

But these cube satellites (CubeSats), known as Binar-2, 3 and 4, entered the atmosphere much sooner than originally planned. They only lasted for two months – a third of what was expected. This significantly reduced valuable time for science and testing new systems.

The reason for their untimely demise? Our Sun has kicked into high gear, and the Binar satellites are far from the only casualty. Recent high solar activity has been causing an unexpected headache for satellite operators in the last few years, and it’s only increasing.

Why is the Sun so active?

Solar activity includes phenomena such as sunspots, solar flares and solar wind – the stream of charged particles that flows toward Earth.

This activity is a product of the Sun’s ever-changing magnetic field, and approximately every 11 years, it completely flips. At the midpoint of this cycle, solar activity is at its highest.

While this cycle is known, specific solar activity is challenging to predict – the dynamics are complex and solar forecasting is in its infancy.

In the last few months, indicators of solar activity were more than one and a half times higher than predictions for this point in the current cycle, labelled solar cycle 25.

The impact of space weather

Space weather refers to the environmental effects that originate from outside our atmosphere (mostly the Sun). It affects us on Earth in a variety of noticeable and unnoticeable ways.

The most obvious is the presence of auroras. In the past few months, auroras have been visible far more intensely and closer to the equator than in the last two decades. This is a direct result of the increased solar activity.

Space weather, and solar activity in particular, also creates additional challenges for satellites and satellite operators.

Higher solar activity means more solar flares and stronger solar wind – resulting in a higher flux of charged particles that can damage or disrupt electrical components on satellites.

It also means an increase in ionising radiation, resulting in a higher dose for astronauts and pilots, and potential disruptions to long-distance radio communications.

But for satellites in low Earth orbit, the most consistent effect of solar activity is that the extra energy gets absorbed into the outer atmosphere, causing it to balloon outward.

As a result, all satellites less than 1,000km from Earth experience a significant increase in atmospheric drag. This is a force that disrupts their orbit and causes them to fall towards the planet’s surface.

Notable satellites in this region include the International Space Station and the Starlink constellation. These satellites have thrusters to counteract this effect, but these corrections can be expensive.

Low Earth orbit also contains many university satellites, such as the Binar CubeSats. Cube satellites are rarely equipped with tools that can adjust their altitude, so they’re entirely at the mercy of space weather.

What happened to Binar?

The Binar Space Program is a satellite research program operating out of Curtin University. It aims to advance our understanding of the Solar System and lower the barrier for operating in space.

The program began operations with its first satellite, Binar-1, in September 2021. This was less than a year into solar cycle 25 when solar activity was relatively low.

In these conditions, the ten-centimetre cube satellite started at an altitude of 420km and survived a full 364 days in orbit.

The program’s follow-up mission – Binar-2, 3, and 4 – were three equally sized CubeSats. However, they were expected to last approximately six months owing to the extra surface area from new deployable solar arrays and a forecast increase in solar activity.

Instead, they only made it to two months before burning up. While cube satellite missions are relatively cheap, the premature ending of a mission will always be costly. This is even more true for commercial satellites, highlighting the need for more accurate space weather forecasting.

The good news is the Sun will calm down again. Despite the current unexpectedly high solar activity, it will likely slow down by 2026, and is expected to return to a solar minimum in 2030.

While this was not an explicit goal of the mission, the Binar Space Program has now poignantly demonstrated the dramatic effects of solar activity on space operations.

While the untimely loss of Binar-2, 3 and 4 was unfortunate, work has already begun on future missions. They are expected to launch into far more forgiving space weather.

Kyle McMullan, PhD Candidate in Aerospace Engineering, Curtin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.