Why NASA observes trees near volcanoes

Scientists have discovered that trees near volcanoes change color when a volcano becomes more active. Now, NASA and the Smithsonian Institution are teaming up to monitor these changes from space.

Before a volcanic eruption, magma rising underground releases gases such as carbon dioxide and sulfur dioxide. Trees absorb the carbon dioxide, making their leaves greener and thicker. Scientists are using satellite imagery from NASA's Landsat 8 to detect this greening, along with data from airborne instruments in the Airborne Validation Unified Experiment: Land to Ocean (AVUELO).

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“Volcano early warning systems exist,” said Florian Schwandner, chief of the Earth Sciences Division at NASA’s Ames Research Center. “The goal here is to make them better and to make them earlier.”

Volcanic eruptions are dangerous and unpredictable. About ten percent of the world's population lives in areas that could be affected. People living near volcanoes face hazards such as flying rocks, ash clouds, and toxic gases. Even those further away can experience mudslides or tsunamis caused by eruptions. Since eruptions cannot be stopped, finding ways to predict them in advance is important for safety.

Detecting volcanic activity from space isn't easy. Scientists can track sulfur dioxide because it's easier to detect, but volcanic carbon dioxide—the first sign of rising magma—is harder to measure.

“A volcano emitting moderate amounts of carbon dioxide that might herald an eruption is not going to show up in satellite images,” said volcanologist Robert Bogue of McGill University.

Traditionally, researchers have had to travel to volcanoes to measure carbon dioxide directly. But with more than 1.300 potentially active volcanoes worldwide, many are in remote, hard-to-reach locations. Monitoring tree responses offers a simpler way to monitor volcanic activity. “The whole idea is to find something we could measure instead of carbon dioxide directly,” Bogue said.

Nicole Guinn, a volcanologist at the University of Houston, used satellite images from Landsat 8, NASA's Terra satellite, and ESA's Sentinel-2 to study trees near Mount Etna in Sicily. Her research found a clear connection between the color of the trees' leaves and volcanic carbon dioxide.

To confirm the accuracy of the satellite images, climatologist Josh Fisher led a ground-based study in March 2025. His team measured carbon dioxide and collected leaf samples from trees near the Rincon de la Vieja volcano in Costa Rica. “Our research is a two-way interdisciplinary intersection between ecology and volcanology,” Fisher said.

Monitoring trees as indicators of volcanic activity has some limitations. Some volcanoes don't have enough trees nearby, and environmental factors like weather and plant diseases can affect tree growth. But the past has shown the potential of this approach.

In 2017, scientists upgraded sensors at the Mayon volcano in the Philippines, detecting signs of an impending eruption. Evacuations were recommended, and more than 56.000 people were moved to safety before the volcano erupted in January 2018.

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