 |
VOOZH | about |
|
VOOZH | about |
Scroll for a step-by-step explanation, or explore the interactive globe on the right on your own!
Viewed from space, a wave of greenness traverses the Earth's surface each year, following the seasons. Over time, this wave reveals how plant growth and health is changing worldwide — shaped by climate change and the transformation of our ecosystems.
There is no established way to measure the wave of greenness over time. For global temperature we use the average, and for sea ice scientists measure its extent. Our new idea is different: we treat greenness like weights spread across the land surface. As this wave of greenness shifts with the seasons, we can track its changing 'center of mass' — the centroid of Earth's green wave.
Think of Earth as a miniature model, with weights added to its surface according to plant greenness. If this model floated in water, it would tilt toward the center of weight—which in reality lies inside the sphere, not on its surface. → 3D Centroid Explorer
At the beginning of the year, it is summer in the Southern Hemisphere and winter in the Northern Hemisphere. Around February, vegetation greenness peaks across much of the south, while northern ecosystems remain largely dormant. At this time, the center of the green wave shifts to its southernmost point. We call this moment the 'viridistice' (from viridis, meaning green), much like the sun's extreme positions are marked by the solstices.
The northern peak of greenness is usually reached in mid or late July. The track shown here is the average from 2000–2023, but in reality, plant growth and the resulting paths vary from year to year and reveal long-term changes (more on that below). Just like the southern viridistice, the northern one occurs about a month after the solstice (June 20/21 and December 20/21). This lag reflects the time plants need to turn the extra sunlight into growing leaves.
The equinox marks the moment when day and night are of equal length. Vegetation greenness, however, does not follow this pattern exactly, since many factors beyond sunlight influence plant growth. We therefore define the equiviridis as the moment when the green wave's centroid moves fastest between hemispheres. In other words, it is the point of most rapid transition of greenness from north to south, or vice versa.
Satellite data on vegetation greenness — which is often an indicator of plant health — can be turned into a simple 'flight path' of the green wave. On average, this path stretches from near the Equator off West Africa up to about 70° North in Scandinavia. These latitudes reflect the larger land masses in the Northern Hemisphere, which pull the centroid northward, compared to the smaller land areas south of the Equator. While the green wave mainly shifts between north and south, it also oscillates east and west. This side-to-side movement is caused by certain regions pulling the centroid their way as plants there begin to green.
When we look at the track year by year (from 2000 to 2023), rather than the average, we see a clear shift of the green wave's centroid toward the North-East. The earlier years lie further south and west, while the more recent years are further north and east. This reflects long-term changes driven by climate change and human activities such as forest expansion or loss, but also more frequent droughts e.g. in Souther America play a role. These shifts have major consequences for ecosystems — for example, they affect when birds migrate, and how much carbon forests can store.
For example, this is where the Southern viridistice was in the year 2000 ...
... and this is where it had moved by 2023.
The eastward shift of the viridistice trend is expected, given that
significant areas of global greening are concentrated in India, China,
and Europe, causing the green wave to be drawn in these directions.
However, the fact that the Southern Hemisphere viridistice trend is
not only moving northward but also stronger than the Northern
Hemisphere trend is unexpected, as we anticipated a moderate southward
movement mirroring the Northern Hemisphere viridistice.
This discrepancy may arise from the extended growing seasons in the
Northern Hemisphere, where larger landmasses allow even slight
enhancements in winter greenery to counteract the southward shift,
which may be constrained by increasing droughts and browning in the
Southern Hemisphere.
→ Global Greening
Multiple different climate models showed similar results and suggest that the Northward shift of the Green Wave will continue under any scenario. → Futures Explorer
This interactive visualization allows users to explore the seasonal dynamics and long-term shifts of Earth's vegetation “green wave”.
Scientific reference: Mahecha, M. D., Kraemer, G., Reinhardt, M., Montero, D., Gans, F., Bastos, A., Feilhauer, H., Flik, I., Ji, C., Kattenborn, T., Migliavacca, M., Mönks, M., Quaas, J., Sippel, S., Walther, S., Wieneke, S., Wirth, C., & Camps-Valls, G. (2026). Accelerated north-east shift of the global green wave trajectory. Proceedings of the PNAS. https://doi.org/10.1073/pnas.2515835123
Interactive design: Ida Flik 🡥
Implementation: Ida Flik 🡥 and Maximilian Söchting 🡥
Funding: This work is a Leipzig University project. The authors thank the European Space Agency for funding the DeepESDL and DeepFeatures projects.
