Scientists know that changing leaves can indicate when nearby volcanoes become more active and may erupt. In a new collaboration between NASA and the Smithsonian Agency, scientists now believe they can detect these changes from space.

As the volcanic magma rises on the above-ground crust, it releases carbon dioxide and other gases that rise to the surface. The trees that account for carbon dioxide become greener and denser. These changes are visible in images of NASA satellites (such as Landsat 8), as well as flying aerial instruments as part of a unified experiment on-board verification: land to ocean (Avuelo).

Ten percent of the world's population lives in areas that are vulnerable to volcanic hazards. People who live or work within miles of an eruption are at risk, including surfing with rocks, dust and hot toxic gases. Further afield, people and property are susceptible to mudslides, ash and tsunamis that can follow volcanic explosions. There is no way to prevent volcanic eruptions, which makes early signs of volcanic activity that is crucial to public safety. According to NASA's Landsat Mission partner, the United States is one of the most active countries in the world.

When the magma rises underground before eruption, it releases gases, including carbon dioxide and sulfur dioxide. Sulfur compounds are easily detected from orbits. However, volcanic CO2 emissions before sulfur dioxide emissions (and provide one of the earliest signs that volcanoes are dormant) are difficult to distinguish from space.

Remote detection of carbon dioxide greening in vegetation may cause scientists to change seismic waves and ground heights to clearly understand what is happening under the volcano. "Volcanic early warning systems exist," said Florian Schwandner, head of the Earth Sciences Division at the NASA AMES Research Center in Silicon Valley, California, who worked with Fisher and Bogue a decade ago. “The purpose here is to make them better and make them earlier.”

"Volcanoes emit a lot of carbon dioxide, but there are so much existing carbon dioxide in the atmosphere that it is often difficult to measure volcanic carbon dioxide. Although major eruptions can drive away enough carbon dioxide to be measured from space through sensors such as NASA Orbital Carbon Observatory 2, detecting these bleak advanced warning signals remains elusive. He added: "A volcano sends a volcano with a moderate amount of carbon dioxide that may indicate the eruption will not appear in satellite images." ”

Therefore, scientists must trek to the volcano to measure carbon dioxide directly. However, around 1,350 potential volcanoes around the world are in remote areas or challenging mountains. This makes monitoring of CO2 at these locations labor-intensive, expensive and sometimes dangerous.

Volcanologists like Bogue join forces with botanists and climate scientists to see trees to monitor volcanic activity. "The whole idea is to find something that can be measured, rather than direct carbon dioxide, to provide us with a proxy for detecting changes in volcanic emissions," Bogue said.

"We can use it to make a lot of satellites," said Nicole Guinn, a volcanologist at the University of Houston. She compared images collected with Landsat 8, NASA's Terra satellite, ESA (European Space Agency) Sentinel-2 and other scorched earth satellites to monitor trees around Etna volcano off the Sicily coast. The Guinn study is the first to show a strong correlation between leaf color and carbon dioxide produced by magma.

Confirmation of ground accuracy in verifying satellite images is a challenge for Chapman University climate scientist Josh Fisher is conducting a survey of trees around the volcano. In March 2025 Airborne Verification Unified Experiment: A spectrometer was deployed on the research aircraft with NASA and Smithsonians to analyze the color of plant life spans in Panama and Costa Rica.

Fisher instructed a team of researchers who collected leaf samples from trees near the active Rincon de la Vieja volcano in Costa Rica, while also measuring carbon dioxide levels. "Our research is a two-way interdisciplinary intersection between ecology and volcanology," Fisher said. "We are interested not only in the response of trees to volcanic carbon dioxide, which is an early warning of eruptions, but also how much trees can occupy, which is a window into the future of the planet, when all trees on Earth are exposed to high levels of carbon dioxide."

Relying on trees as agents of volcanic carbon dioxide has its limitations. Many volcanoes have climates that are not enough for satellite imagery. In some forest environments, the response to changing levels of carbon dioxide is different. Fires, changes in weather conditions, and plant diseases can complicate the interpretation of satellite data on volcanic gases.

Still, Schwanner witnessed the potential benefits of volcanic carbon dioxide observations firsthand. He led a team that upgraded the monitoring network of Mayon volcano in the Philippines, which includes carbon dioxide and sulfur dioxide sensors. In December 2017, government researchers in the Philippines used the system to detect signs of an upcoming eruption and advocated a massive evacuation of areas around the volcano. More than 56,000 people were safely evacuated before the massive outbreak began on January 23, 2018. Due to early warnings, no casualties were found.

Using satellites to monitor trees around volcanoes will give scientists an early insight into more volcanoes and warn of future eruptions in advance. "No volcanoes have a signal that is a silver bullet," Schwanner said. "And tracking the effect of volcano carbon dioxide on trees will not be a silver bullet. But it will be something that can change the game."

By James Riordon
NASA's Earth Science News Team

Media Contact: Elizabeth Villock
NASA Headquarters