Chaitén Volcano in southern Chile erupted on May 2, 2008, for the first time in 9,000 years. This unexpected event highlighted the urgent need for better eruption prediction tools. Today, thanks to advanced satellite technology, scientists are discovering that trees might offer a crucial clue — visible even from space.
Credit: Jeff Schmaltz, MODIS Rapid Response Team, NASA Goddard Space Flight Center

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A New Perspective from Above: Trees as Early Warning Signals

In a groundbreaking collaboration, scientists from NASA and the Smithsonian Institution have found that trees growing near volcanoes may signal volcanic unrest before an eruption occurs. The key lies in a subtle but significant change: surrounding vegetation becomes greener due to carbon dioxide (CO₂) released from rising magma.

Using satellite imagery and field research, scientists are now building a powerful early warning system that could one day help prevent widespread disaster. By detecting the effects of volcanic gases on trees, this system has the potential to warn communities weeks or even months before a volcano erupts.

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The Science: Carbon Dioxide Makes Trees Greener

When magma rises through the Earth’s crust, it releases gases — especially carbon dioxide. As this gas seeps into the surrounding soil and atmosphere, nearby trees absorb it through their roots and leaves. The added CO₂ acts like a fertilizer, triggering lush growth and greener foliage — a phenomenon visible through satellite sensors.

This increase in photosynthetic activity and canopy density can now be observed using Earth-monitoring tools such as NASA’s Landsat 8 satellite, as well as airborne instruments flown in missions like the Airborne Validation Unified Experiment: Land to Ocean (AVUELO).

The goal? To detect the earliest signs of volcanic unrest before other traditional indicators like tremors or ground deformation become apparent.

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Case Study: Bubbling Gases in Costa Rica

Near the Rincón de la Vieja volcano in Costa Rica, researchers observed carbon dioxide bubbling up through geothermal pools — a clear sign of rising magma activity. This same gas, when absorbed by surrounding forests, alters the ecosystem in measurable ways.

Credit: Alessandra Baltodano / Chapman University

These types of signals could serve as the earliest detectable warnings of volcanic behavior, particularly in remote or poorly monitored regions.

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The Importance of Early Detection

Around 10% of the global population lives in areas vulnerable to volcanic hazards. For these communities, early warnings can be the difference between life and death. Volcanic eruptions can unleash a cascade of threats — from flying debris and ashfall to pyroclastic flows and even tsunamis.

While we cannot prevent an eruption, detecting the subtle signals beforehand gives scientists and emergency agencies time to act. Timely evacuations and preparations can save thousands of lives and reduce economic loss.

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The CO₂ Challenge: An Elusive Signal

Although sulfur dioxide (SO₂) emissions from volcanoes are easier to detect with satellites, CO₂ — which often escapes earlier — is much harder to isolate. That’s because background atmospheric CO₂ levels are already high and variable, making it tricky to attribute small increases to volcanic sources.

“Volcanoes emit a lot of carbon dioxide,” says volcanologist Robert Bogue of McGill University. “But modest amounts of CO₂, the kind that could signal early volcanic activity, are often lost in the noise.”

That’s why scientists have taken a different approach: instead of measuring the gas directly, they measure how trees react to it.

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On the Ground: Sensors, Slingshots, and Science

In Costa Rica, researchers like Gregory Goldsmith of Chapman University are deploying CO₂ sensors in forest canopies — sometimes using slingshots to launch equipment into treetops.

Credit: Alessandra Baltodano / Chapman University

These on-the-ground efforts support what satellites observe from space, creating a more complete picture of how carbon dioxide influences local vegetation before an eruption.

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Photosynthesis and Proxy Signals

To verify the green-up effect, scientists such as Alexandria Pivovaroff of Occidental College measure photosynthesis levels in tree leaves collected from volcano-adjacent forests.

This "greening" becomes a proxy signal — an indirect but measurable indicator of rising volcanic gas emissions. Using vegetation as a proxy offers a safer, more scalable method to monitor hundreds of active and dormant volcanoes around the world.

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Expanding the Toolkit: Satellites and Synergy

Volcanologist Nicole Guinn of the University of Houston has compared tree behavior around Mount Etna in Sicily using satellite data from multiple missions, including NASA’s Terra and the European Space Agency’s Sentinel-2. Her research demonstrated a strong link between tree color and volcanic CO₂ levels — confirming that satellite-based vegetation monitoring can reflect underground volcanic processes.

“There are plenty of satellites we can use to do this kind of analysis,” Guinn said. “It’s about interpreting the data in the right context.”

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Airborne Missions: Validating Space Data

In March 2025, during the AVUELO campaign, scientists flew over forests in Panama and Costa Rica, collecting data with spectrometers that analyzed vegetation health from above. On the ground, researchers gathered leaf samples and measured CO₂ levels directly in the canopy.

“It's an interdisciplinary intersection between ecology and volcanology,” said Josh Fisher of Chapman University, who led the effort. “We want to understand not only if trees can warn us about eruptions but also what their responses tell us about Earth's future in a high-CO₂ world.”

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Caveats and Challenges

Despite its promise, using trees as eruption indicators has limitations:

• Some volcanoes are located in non-forested regions, limiting the usefulness of satellite vegetation monitoring.

• Trees may respond differently depending on species, soil type, and climate.

• External factors such as wildfires, droughts, or disease can skew vegetation readings and confuse signals from volcanic activity.

Still, experts believe this approach can add a vital new layer to volcanic monitoring systems.

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Success Stories: When Early Warnings Save Lives

In 2017, scientist Florian Schwandner helped upgrade the monitoring system at Mayon volcano in the Philippines, adding CO₂ and SO₂ sensors. Just weeks later, those sensors detected signs of imminent eruption. Over 56,000 people were evacuated, and when the volcano erupted in January 2018, no lives were lost.

It was a powerful demonstration of how enhanced early warning systems can protect lives — especially in high-risk regions.

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Looking Ahead: A Game-Changing Tool

Using satellites to observe trees near volcanoes could become a game-changing component of eruption forecasting. It’s not a silver bullet, experts say, but it could become a crucial puzzle piece.

“There’s no single signal from volcanoes that tells the full story,” said Schwandner. “But vegetation changes — especially when combined with other data — could give us a faster, more accurate picture of volcanic activity.”

As technology improves and satellite coverage expands, the hope is to monitor more volcanoes in more places — in near real-time — with help from the living sensors that surround them: trees.