Ilaria Rosella Pagliaro A new global map reveals how seasons no longer follow predictable patterns, creating divergences even between very close areas
Earth’s seasons no longer flow in unison and are changing in unexpected ways. A recent study published in Nature, conducted through the analysis of twenty years of satellite data, has revealed that vegetation cycles follow increasingly divergent rhythms depending on the zones, even between territories separated by just a few kilometers (a couple of miles).
Once considered cyclical and predictable, the seasons now show surprisingly irregular patterns of plant growth, especially in tropical mountain areas and transitional climates. Scientists have identified true “seasonal asynchrony hotspots,” where the biological cycles of plants are strongly out of phase, challenging traditional notions about seasons.
A detailed map of plant phenology
©Nature
Under the guidance of ecologist Drew Terasaki Hart from CSIRO, the team developed the most precise map ever created of plant phenology – that is, the set of seasonal biological events – on a planetary scale. This high-resolution map shows how plant growth cycles vary significantly even within the same ecosystem, in response to local climatic and geographic factors.
In high-latitude territories, seasons maintain a relatively predictable pattern: growth in spring, dormancy in winter. But elsewhere, especially in the tropics and arid areas, vegetation grows in irregular cycles, driven by intermittent rains or soil characteristics.
A striking example comes from the southwestern United States: Phoenix and Tucson, though only 100 miles (160 kilometers) apart, record distinct seasonal patterns, the result of local microclimates. Such temporal fragmentation radically changes the way we read and interpret seasons.
Mediterranean ecosystems and arid zones
Particularly evident are the seasonal asynchronies in the five main Mediterranean climate ecosystems on the planet: California, Chile, southern Australia, South Africa, and the Mediterranean basin. These zones, characterized by mild, rainy winters followed by dry, hot summers, show a “double peak” in plant growth, with forests reaching their apex about two months later than other nearby vegetation types.
According to reports also from ScienceAlert, this phenomenon generates obvious contrasts in seasonal timing, especially at points where Mediterranean climates border arid areas dominated by summer rains. The result is “hotspots” of temporal asynchrony, where just a few miles apart there are completely out-of-phase vegetation cycles, challenging traditional ecological models.
These differences represent a crucial challenge for ecological research: local variations affect not only agricultural productivity and land management, but also relationships between plant and animal species.
The phenomenon of seasonal asynchrony often overlaps with the planet’s most biodiverse areas. This suggests that temporal variations in biological cycles may play a role in the evolution of life itself. Differences in flowering times, pollination, or resource availability can interfere with the reproductive synchronization of plants and animals, even within the same species.
The study reveals that populations separated by just a few hours of travel – such as those growing coffee in the Colombian mountains – experience reproductive cycles as different as those of opposite hemispheres. This desynchronization can limit genetic exchange between nearby groups and, over time, favor the formation of new species, contributing to the complexity and variety of life on Earth.
Source: Nature
