Trees as volcanic sentinels: nature whispering the secrets of moving magma. This is the outcome of an innovative volcanic monitoring approach developed by NASA in collaboration with the Smithsonian Institution. While scientists have traditionally relied on expensive instrumentation and dangerous field missions to study volcanic activity, they are now turning to natural indicators that could revolutionise early warning systems.

The vegetation surrounding volcanoes reacts measurably to underground changes that precede eruptions, potentially offering a natural warning system visible even from space. When green becomes a harbinger of danger, The principle behind this discovery is surprisingly simple. As magma begins its journey towards the surface, it releases significant quantities of gases, mainly carbon dioxide (CO₂) and sulphur dioxide. CO₂ is absorbed by the surrounding plants, which, instead of suffering, show a positive biological response: they become greener and lusher. This “greening” phenomenon represents a physiological response that, to the attentive eyes of the satellites, turns into a potential alarm signal.

Between Italy and Costa Rica

Data collected by orbital instruments such as NASA’s Landsat 8 and the European Space Agency’s Sentinel-2 are analysed to identify suspicious variations in leaf colouration. Nicole Guinn, a volcanologist at the University of Houston, applied this methodology to study Etna in Sicily, collecting results that support the validity of the approach. Confirmation in the field also came through the work of climatologist Josh Fisher, who, in March 2025, verified that leaves collected near the Rincon de la Vieja volcano in Costa Rica showed high levels of CO₂, perfectly in line with what was observed by satellite images.

The value of NASA’s method becomes particularly evident when one considers the magnitude of the challenge: with more than 1,300 active volcanoes spread across the globe, many of them in remote or difficult-to-access areas, traditional monitoring is often impractical or excessively risky. Plants offer an elegant alternative: natural sensors already distributed around volcanoes, reacting in real time to underlying geochemical changes.

However, like any scientific approach, this, too, has its limitations. Not all volcanoes are surrounded by sufficiently dense or reactive vegetation to provide clear signals. Furthermore, external factors such as heavy rainfall, seasonal changes or plant diseases can interfere with the interpretation of the data. The challenge lies in the ability to distinguish genuine volcanic signals from these confounding variables.

An integrated system to save lives

Experience shows how crucial a multimodal approach to eruptive forecasting is. In 2017, a comprehensive monitoring system was installed around the Mayon volcano in the Philippines, which made it possible to detect premonitory signs of an impending eruption. The early warning enabled the evacuation of more than 56,000 people from areas at risk, a prime example of how technology can translate into lives saved.

Florian Schwandner, head of the Earth Sciences Division at NASA’s Ames Research Center, emphasises a key point: ‘There is no perfect indicator to predict when a volcano will erupt. Our goal is to improve existing systems and make them faster and more accurate. In this vision, plant response analysis is an important piece of a larger mosaic of complementary technologies.

CO₂, although difficult to detect directly from space, leaves significant imprints on the ecosystems surrounding volcanoes. This indirect approach, which uses nature as a mediator between geological phenomena and human observation, could represent a substantial development in volcanological science. Trees, silent witnesses to underground activity, could thus become the first to sound the alarm well before magma reaches the surface. NASA knows that.

The prospect is more relevant when considering the potential impact: on a planet where hundreds of millions of people live in the vicinity of active volcanoes, even a small improvement in emergency response times can translate into a significant number of lives saved. It is a curious irony that, in the age of ultra-sophisticated sensors and state-of-the-art satellites, it may be the planet’s oldest organisms – trees – that offer us one of the most promising keys to volcanic safety in the future.