In the heart of Yellowstone National Park, where the earth whispers tales of ancient volcanic activity, scientists have discovered a new way to listen to these whispers through the health of the trees. A recent study by Robert Bogue and his team has shown that we can uncover hidden volcanic activity years before it becomes visible or thermally evident by observing how plants respond to volcanic gases.
The study focused on the Tern Lake Thermal Area (TLTA) within Yellowstone, a region known for its rich hydrothermal features but not previously identified for active volcanic activity until around 2000. However, Bogue’s team found that the signs were there long before, just not in the ways we were looking. By analyzing 185 images from the Landsat 5 and 8 satellites from 1984 to 2022, researchers measured the health of vegetation through the Normalized Difference Vegetation Index (NDVI). This measure reflects how well plants are photosynthesizing.
What they found was astonishing. From 1984 to 1999, the NDVI values in the TLTA were higher than in nearby, unaffected forests, suggesting that the plants were thriving on something extra – possibly the increased levels of CO2 or water from volcanic emissions. This period marked a subtle yet significant enhancement in plant health, with NDVI values typically from 0.40 to 0.70, indicative of dense, green vegetation.
Robert Bogue explains, “We noticed that the vegetation in the thermal area was healthier than in the surrounding forests, which suggested that volcanic CO2 was acting like a fertilizer, encouraging growth.” This was a revelation because it meant that volcanic activity could be influencing plant life long before it escalated to more visible signs like dead trees or hot ground.
The plot thickened around 1999 when the NDVI values started to change. Initially, there was a brief period where plant health in TLTA peaked, with NDVI metrics dipping below zero in 2001, signaling a surge in CO2 or water availability that boosted plant growth. However, this was short-lived. By 2006, the narrative flipped as the NDVI metrics began to soar, indicating severe stress to the plants due to increasing soil temperatures, sulfur emissions, and potentially lethal levels of CO2. The study pinpointed that the least healthy plants were in the areas where hydrothermal activity was about to peak.
This shift was not just a local story. It’s a narrative about how we can use nature itself as a sentinel for geological events. The study’s implications are profound – if we can detect these changes in plant health from space, we could monitor volcanoes worldwide that are too remote or dangerous for ground surveys. This could revolutionize volcano monitoring, providing a safer, more accessible method.
Reference
Bogue, R. R., J. Douglas, P. M., Fisher, J. B., & Stix, J. (2023). Volcanic Diffuse Volatile Emissions Tracked by Plant Responses Detectable From Space. Geochemistry, Geophysics, Geosystems, 24(11), e2023GC010938. https://doi.org/10.1029/2023GC010938
