Humans and other mammals may only exist for another 250 million years on Earth — which is about as long as mammals have existed here at all — according to a new study that predicts the continents will collide and form one massive block of land that is too hot and too dry to live on.
The study, published Monday in the journal Nature Geoscience, relayed the findings of a computer-simulated future Earth that forecasts continental shifts and atmospheric changes. It suggests that in 250 million years, the land on our planet will have melded into one volcanic supercontinent, which researchers called Pangea Ultima, situated in the Earth's tropical region along the equator. It would not be the first supercontinent to appear on our planet, as past geological research has shown that an original supercontinent, called Pangea, existed between about 300 million and 180 million years ago before beginning to break apart and shift slowly into continental structures that exist now.
Researchers said the new model indicates that collisions between land masses to form Pangea Ultima could create a supercontinent riddled with volcanoes that release carbon dioxide. The altered terrain, coupled with increased solar energy and higher concentrations of carbon dioxide in the atmosphere, will likely render conditions on Pangea Ultima "inhospitable to mammals," the study predicts, noting that the forecast carbon dioxide levels combined with a brighter sun "will probably lead to a climate tipping point" that causes the "mass extinction" of Earthly mammals, humans included.
"We show that the assembly of Pangea Ultima in 250 million years will likely lead to extreme heat that could lead to the mass extinction of mammals and other life," tweeted Alex Farnsworth, a meteorologist and paleoclimate modeler at the University of Bristol, who is the study's lead author, on Monday. Farnsworth referenced an animation demonstrating sharp increases in monthly surface temperatures across the future supercontinent over the course of one year.
"Mammals are evolutionary one of the great survivor species, adept of living in many climates and environments since they became dominant after the K/Pg," Farnsworth wrote. The K/Pg, short for Cretaceous-Paleogene, was a mass extinction event on Earth that wiped out all non-avian dinosaurs roughly 66 million years ago. Scientists have estimated that the earliest mammals appeared on Earth somewhere between 170 million and 225 million years ago, with humans' earliest documented predecessors emerging much later.
Despite surviving the dinosaur extinction, mammals also have "thermal physiological limits," meaning they can only tolerate a certain range of temperatures, "which threaten their existence," Farnsworth noted. And, as the new study suggests, "much of the supercontinent will straddle the tropics, making it very hot and dry in the interiors as well as hot and humid around the coasts," he said. Most of the land on Pangea Ultima is forecast to run warmer than 40 degrees Celsius, or 104 degrees Fahrenheit, during the warmest months of the year, with very little rainfall throughout, according to the findings.
And as scientists continue to studyin search of environments capable of sustaining life beyond Earth, Farnsworth said his team's new research may offer valuable insight into how tectonics play a role in what makes a place habitable — or not. He shared a diagram that compares other planets and moons in the Solar System, like Mars, Venus, Jupiter, Saturn and the Saturnian moon Titan, in terms of their habitability and similarity to Earth in the modern day. In terms of similarity to our modern planet, Pangea Ultima ranked somewhere between Venus and Mars, and much closer to Venus.
So, Farnsworth wrote, "even though the Earth will still be in the 'habitable zone' for our sun, such an index would suggest it's not so habitable, showcasing the importance of tectonics in exoplanet research."
Researchers who worked on the study also suggested that life in general could become extinct on Pangea Ultima, if temperatures rise to such an extent that plants are unable to perform photosynthesis, which would eventually mean very little oxygen could remain in the atmosphere. They noted that more research is needed to estimate how plants might adapt in that future environment, though.
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