Earth’s Next Supercontinent Could Wipe Out Mammals in 250 Million Years

In 250 million years, the vast majority of Earth could become inhospitable to mammals as the planet’s landmasses merge together to form the next supercontinent. At least, that’s the dire outlook of a new study published Monday in the journal Nature Geoscience.

Scientists reached this conclusion by modeling the climate with a supercomputer—and while they weren’t completely surprised by the result, they do find the predictions “a bit depressing,” says Hannah Davies, a geologist at the GFZ German Research Center for Geosciences who was not involved in the study, to Nature News’ Jonathan O’Callaghan.

“There have been extinction events in the past and will be extinction events in the future,” she tells the publication. “I think life will make it through this one. It’s just kind of a grim period.”

A supercontinent is just what it sounds like: a giant landmass that forms when the planet’s continents join together because of shifting tectonic plates. The last supercontinent that existed on Earth was called Pangea, and it split up roughly 200 million years ago.

Earth’s continents are drifting now, and they could merge back together in 250 million years, scientists predict. They’ve named the next supercontinent Pangea Ultima. And according to the new model, it will be a kind of hellscape.

When Pangea Ultima forms, volcanic activity will increase, blasting carbon dioxide into the atmosphere, the researchers posit. Because much of the supercontinent will be flat and far from the ocean, the scientists also predict a slowing of the CO2-trapping chemical reactions that typically take place between rock and water, reports Science’s Elise Cutts.

At the same time, the aging sun will likely shine 2.5 percent brighter than it does today, which means Earth will be a target of more intense solar radiation.

With all this CO2, extra sunlight and other changes, the planet could heat to between 104 and 122 degrees Fahrenheit in many places, with even higher daily extremes, according to a statement.

The world as we know it could become “very toasty,” as study co-author Alexander Farnsworth, a climatologist at the University of Bristol in England, tells the New York Times’ Carl Zimmer.

Coastal areas would have the most livable climate, while interior parts of the supercontinent could turn into deserts, where only specially adapted animals could survive. Perhaps coldblooded reptiles, for example, could become the dominant creatures on Earth, reports Live Science’s Ben Turner.

The researchers did not factor human-caused carbon emissions into their model, which are currently warming the planet. But by the time Pangea Ultima forms, CO2 levels could double naturally to as high as 1,120 parts per million (today, CO2 levels are around 418 parts per million). Under that worst-case scenario, just 8 percent of Earth’s surface would be hospitable to mammals, mostly the polar and coastal regions. For comparison, 66 percent of the surface was habitable by mammals during the pre-industrial era.

Though the study predicts what Earth will be like in the distant future, the researchers warn that it’s “crucial” to reach net-zero carbon emissions as soon as possible, because “today we are already experiencing extreme heat that is detrimental to human health,” study co-author Eunice Lo, also a climatologist at the University of Bristol, says in the statement.

And what about humans in 250 million years, if the species still exists by then? They might find ways to adapt to their new environment, such as by only being active at night or living in cooler caves.

Plus, certain factors might make Pangea Ultima more habitable than predicted in this study. For one, the climate might be cooler if the supercontinent forms near a pole, writes Nature News. And the amount of heat escaping from the interior of Earth might decrease as the planet ages, resulting in fewer volcanic eruptions than projected, reports the New York Times.

If possible, however, it might be better for humans to “get off this planet and find somewhere more habitable” to live, as Farnsworth tells Nature News.

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.