by German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig
edited by Gaby Clark, reviewed by Robert Egan
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Add as preferred source The greenness of the Earth's terrestrial vegetation changes throughout the seasons. Researchers can calculate the global "green center" and track its movement over several decades. They have observed a gradual shift towards the north-east. Credit: Ida Flik A team of scientists led by the German Center for Integrative Biodiversity Research (iDiv), the Helmholtz Center for Environmental Research (UFZ), and Leipzig University has developed a new method to track Earth's greenness—a key indicator of vegetation health and activity—by calculating its center of mass.
Lead author Prof. Miguel Mahecha explains, "Imagine holding a perfectly round globe in your hands and attaching small weights to it, each representing the green leaves at every point on Earth's surface. If you then carefully place this globe into calm water, the center of mass will always point downward." Mahecha is a researcher at Leipzig University, the Helmholtz Center for Environmental Research (UFZ), and a member of iDiv.
Earth's green center shifts continuously
Using satellite observations and model data, the researchers tracked how this "green center" shifts over time. In rhythm with the seasons, vegetation greenness moves like a green wave from north to south and back each year. By tracking the center of this wave—its direction and velocity—the team found it oscillating between its northernmost position in mid-July in the North Atlantic near Iceland and its southernmost position off the coast of Liberia in March.
The study, published in the journal Proceedings of the National Academy of Sciences, sheds new light on global greening and its acceleration—a less widely known aspect of global change referring to the overall increase in vegetation density worldwide. Like climate and biodiversity change, global greening is largely driven by human activities. Rising atmospheric CO₂ acts as a fertilizer, enhancing photosynthesis, while higher temperatures extend growing seasons in many regions.
When analyzing changes in the green wave over several decades, the researchers detected a consistent northward shift across all seasons. Contrary to their expectations, they did not observe a southward shift during the Southern Hemisphere summer.
- In April, the forests of Central Europe begin to turn green. At this time of year, the "green center" of global vegetation shifts northward. The photo shows the Hainich National Park in Thuringia. Credit: Stefan Bernhardt
- In the tropics, the greenness of the vegetation varies only slightly. The photo shows an evergreen tropical rainforest in the Sierra Nevada, Colombia. Credit: Miguel Mahecha
"This was a huge surprise to us," says Mahecha. "Longer growing seasons and warmer winters in the Northern Hemisphere, which allow vegetation to remain slightly greener for longer, may be driving Earth's overall greening shift throughout the year. However, this is a hypothesis that we need to explore further."
In addition to the northward movement, the team also identified a distinct eastward shift. According to the researchers, this pattern is likely linked to pronounced greening hotspots in eastern regions such as India, China, and Russia.
Tracking Earth's seasonal greening and effectively measuring how fast and in which direction it is changing connects multiple facets of global change, including climate–biosphere interactions, land-use change, fire dynamics, droughts, and animal migration. The new method therefore provides a powerful tool for understanding how the living surface of our planet is reorganizing in a warming world.
Accelerated north-east shift of the global green wave trajectory, Proceedings of the National Academy of Sciences (2026). DOI: 10.1073/pnas.2515835123
Journal information: Proceedings of the National Academy of Sciences
Provided by German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig
