Unprecedented portrait of seasonal cycles reveals critical points with ecological, evolutionary and even economic consequences.
The annual cycle of stations – winter, spring, summer, autumn – is often given as certain. But a new study at Nature, which uses a new approach to observing seasonal growth cycles from satellites, shows that this notion is very simplistic.
The study brings an intimate and unprecedented portrait of the seasonal cycles of the earth’s earthly ecosystems. It reveals “Critical Points“Seasonal asynchrony worldwide – regions where seasonal cycles time may be out of sync between nearby places.
These time differences can have ecological, evolutionary and even surprising economic consequences.
The stations of the year, views of space
The stations define the rhythm of life. Living beings, including humans, adjust the time of their annual activities to explore resources and conditions that float throughout the year.
The study of this calendar, known as phenologyit is a millennial way of observing nature by human being. But today we can also observe phenology from space.
With satellite image files that cover decades, we can use computing to better understand seasonal cycles of plant growth. However, the methods to do this are usually based on the assumption of simple seasonal cycles and distinct growth stations.
This works well in much of Europe, North America and other high latitude places with strict winters. But the method may have difficulties in the tropics and arid regions. In these places, estimates of satellite -based plant growth may vary subtly throughout the year without well -defined growth stations.
Amazing standards
By applying a new analysis to 20 years of satellite images, the team has created a more accurate map of plant growth cycles calendar worldwide. Beyond the expected standards, such as the Spring delay In higher latitudes and altitudes, we also observed others more surprising.
A surprising pattern occurs in the five Mediterranean climate regions of the Earth, where winters are mild and humid and summers are hot and dry. These include California, Chile, South Africa, southern Australia and the Mediterranean itself.
All of these regions share a seasonal peak double patternpreviously documented in California, because forest growth cycles tend to reach peak about two months later than in other ecosystems. They also have striking differences in plant growth time compared to neighboring arid lands, where summer rainfalls are more common.
Critical Points
This complex mix of seasonal activity patterns explains an important discovery of the work: Mediterranean climates and neighboring arid lands are critical points of seasonal activity out of synchronization. In other words, they are regions where Seasonal cycles of nearby places may have drastically different times.
Other global critical points occur mainly in the tropical mountains. Complex patterns of out of sync stations that we observe in these regions may be related to complex forms how mountains influence air flow, determining local standards of seasonal precipitation and cloudiness. These phenomena are still little understood, but may be fundamental to the distribution of species in these exceptional biodiversity regions.
Seasonality and biodiversity
Identifying global regions where seasonal standards are out of synchronization was the original motivation for the new work. And the discovery that they overlap many of the Earth’s critical points of the Earth – local with a large number of plant and animal species – may not be a coincidence.
In these regions, such as seasonal plant growth cycles may be out of sync between nearby places, seasonal availability of resources may also be out of sync. This would affect seasonal reproductive cycles of many species, and ecological and evolutionary consequences could be deep.
One of these consequences is that populations with reproductive cycles out of sync would be less likely to cross. As a result, these populations would be expected to genetically diverge and perhaps eventually divided into different species.
If that happened even if it were a small percentage of species at any time, then, in the long run, these regions would produce large amounts of biodiversity.
