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Scientists at the University of California, Berkeley, have watched our planet’s seasons from space and discovered that spring, summer, winter, and fall are surprisingly out of sync.
Just because two places exist in the same hemisphere, at similar altitudes, or at the same latitude doesn’t guarantee they’ll experience the same seasonal changes at the same time.
Even regions that are side by side can experience different weather and ecological patterns, sculpting wildly different neighboring habitats.
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It’s similar to how time zones can separate two adjacent spots, but in this case, the boundary is drawn by nature itself.
Watch the video below for a summary:
“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,” biogeographer and lead author Drew Terasaki Hart said in August when the new map was published.
“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.”
Using 20 years of satellite data, Terasaki Hart and his team have created what they say is the most comprehensive map to date of the seasonal timing of Earth’s terrestrial ecosystems.
The new map identifies global regions where seasonal patterns are particularly out of sync, and these asynchronies often occur in biodiversity hotspots.
That is probably no coincidence. More variability in weather patterns can have trickle-down effects, which may drive greater diversity within habitats.
For example, if natural resources in two neighboring habitats are made available at different times of the year, it could shape the ecology and evolution of flora and fauna in each spot.
It could even mean that a species in one habitat reaches its reproductive season before or after the same species in an adjacent habitat, preventing interbreeding.
Across many generations, this can lead to the evolution of two entirely separate species.
Two cities in Arizona, Phoenix and Tucson, serve as another example. These urban hubs are only 160 kilometers (99 miles) apart, yet their annual climate rhythms are on entirely different wavelengths.
Tucson experiences its highest amount of rainfall during the summer monsoon season, whereas Phoenix receives most of its rain in January, and this has trickle-down effects on their ecosystems.
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One intriguing pattern revealed by the new map was that Earth’s five Mediterranean climate regions – which have mild, wet winters and hot, dry summers – showed forest growth cycles that peaked roughly two months after other ecosystems.
This incongruency occurred in places such as California, Chile, South Africa, southern Australia, and, of course, the Mediterranean.
The map also lays out variances in when flowering plants bloom and crops are ready to harvest.
“It even explains the complex geography of coffee harvest seasons in Colombia – a nation where coffee farms separated by a day’s drive over the mountains can have reproductive cycles as out of sync as if they were in opposite hemispheres,” Terasaki Hart said.
Today, many ecological predictions are based on simple models of Earth’s seasons, but if we really want to know how the climate crisis will impact our planet and our health, we need to consider variations from place to place, even if they are close by.
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In October, samples from under sea ice in the Central Arctic Ocean and the Eurasian Arctic revealed a community of thriving microbes called non-cyanobacterial diazotrophs (NCDs). These are nitrogen-fixing bacteria that don’t photosynthesize.
Researchers have not yet shown that these NCDs are fixing nitrogen in the Arctic. If that’s true, these microscopic life forms could have a global impact.
They found the fringes of Arctic sea ice tend to host more nitrogen-fixing bacteria and higher nitrogen-fixing activity. This suggests that as Arctic ice rapidly melts with climate change, more of these NCDs – which feed algae – may proliferate, altering the marine food web and impacting the atmosphere itself.
“If algae production increases, the Arctic Ocean will absorb more CO2 because more CO2 will be bound in algae biomass,” says University of Copenhagen marine microbial ecologist Lasse Riemann.
Riemann argues that nitrogen fixers in the Arctic need to be incorporated into future climate models.
As Terasaki Hart explains, climate or conservation models that make blanket assumptions about the seasons don’t take into account the fullness of our planet’s great diversity.
“We suggest exciting future directions for evolutionary biology, climate change ecology, and biodiversity research, but this way of looking at the world has interesting implications even further afield, such as in agricultural sciences or epidemiology,” Terasaki Hart said.
The study was published in Nature.
