The study used 20 years of satellite vegetation data to create a global map showing that seasonal timing can change sharply over short distances, even at the same latitude. Tropical mountain slopes and Mediterranean-climate regions showed the strongest local asynchrony, driven more by light and water availability than by temperature. These mismatched seasonal schedules can promote reproductive isolation, boost biodiversity, and affect agricultural timing such as coffee harvests in Colombia.
New Map Shows Earth's Seasonal Timing Can Shift Sharply Over Short Distances — Even On The Same Latitude
Tropical montane landscapes like this one tend to have seasonal cycles that vary widely over short distances, a new study finds. | Credit: Michele D'Amico supersky77/Getty Images
New research shows that the timing of seasonal cycles — such as the start and end of the growing season — can vary dramatically across very short distances, even between locations on the same latitude. The study’s high-resolution global map of vegetation rhythms reveals pockets of strong seasonal asynchrony that help explain biodiversity patterns, agricultural timing differences and broader ecological dynamics.
Researchers led by Drew Terasaki Hart of the Commonwealth Scientific and Industrial Research Organization (CSIRO) analyzed 20 years of satellite observations that capture how vegetation reflects infrared light (vegetation indices such as NDVI/EVI) throughout each year. From this dataset they derived the timing and shape of annual growth cycles for plants across the globe and identified regions where those cycles change rapidly over short distances.
Areas with the most striking local differences included tropical mountain slopes and zones with Mediterranean-style climates. In these places, local availability of light and water — rather than average temperature alone — often controls plant growth timing, producing neighboring patches with markedly different seasonal calendars.
“Seasonality may often be thought of as a simple rhythm — winter, spring, summer, fall — but our work shows that nature’s calendar is far more complex,” said study co-author Drew Terasaki Hart, an ecologist and data analyst at CSIRO. “This is especially true in regions where the shape and timing of the typical local seasonal cycle differs dramatically across the landscape. This can have profound implications for ecology and evolution in these regions.”
The authors point to practical examples: in Colombia, coffee farms separated by just a day’s drive over mountain terrain can have reproductive and harvest cycles as out of sync as farms in opposite hemispheres. Such fine-scale mismatches in seasonal timing can create distinct reproductive schedules, which over many generations may promote genetic divergence and the formation of new species.
Beyond explaining patterns of terrestrial biodiversity, the researchers say this approach can be applied to riverine and marine systems and used to track ecological responses to climate change. The insights may also inform agriculture, conservation planning and even epidemiology by highlighting where biological cycles — flowering, migration, disease risk — are likely to be out of phase across short distances.
Study details: The research used two decades of satellite-derived vegetation indices to map the timing and shape of plant growth cycles worldwide and was published Aug. 27 in the journal Nature.
