Future Timeline

If Pangea Ultima behaves like previous supercontinents, it will become studded with volcanoes that belch carbon dioxide, the model found. Thanks to the turbulent movements of molten rock deep in the Earth, the volcanoes may release vast surges of carbon dioxide for thousands of years — blasts of greenhouse gases that will make temperatures rocket up.

On Pangea Ultima, Dr. Farnsworth and his colleagues concluded, things will probably get far worse for mammals like us. The researchers found that almost all of Pangea Ultima could easily become too hot for any mammal to survive. They might disappear in a mass extinction.

Dr. Farnsworth granted that a few mammals might eke out an existence in refuges on the fringes of Pangea Ultima. “Some areas in the northern and southern peripheries could be survivable,” he said.

Even so, he was confident that mammals would lose the dominance they’ve enjoyed for the past 65 million years. They might be replaced by coldblooded reptiles that could tolerate the heat.

The mass extinction would be caused primarily by heat stress as a result of greater volcanic activity that would put twice as much carbon dioxide into the atmosphere as current levels, an older sun that would emit more radiation and the extent of inland deserts in the tropics.

While there are large uncertainties when making predictions so far into the future, the scientists said that the picture appears “very bleak,” with only around 8% to 16% of land on the supercontinent habitable for mammals.

Increased competition between species due to the merging of continental landmasses and the possibility of increased volcanic emissions from deep mantle superplumes, combined with generally less hospitable conditions on the warming Earth could lead to a mass extinction event for plants and animals from which they may not be able to recover.