New supercontinent could drive mammals to extinction – 09/29/2023 – Science

It has been about 250 million years since reptile-like animals evolved into mammals. Now, a team of scientists is predicting that mammals may only have another 250 million years to live.

The researchers built a virtual simulation of our future world, similar to the models that projected human-caused global warming over the next century. Using data on the movement of continents across the planet, as well as fluctuations in the chemical composition of the atmosphere, the new study projected much further into the future.

Alexander Farnsworth, a paleoclimate scientist at the University of Bristol who led the team, said the planet could become too hot for any mammals — including ourselves — to survive on land. Researchers found that the climate will become deadly due to three factors: a brighter Sun, a change in the geography of continents and an increase in carbon dioxide.

“It’s a triple whammy that becomes unbearable,” Farnsworth said. He and his colleagues published their study last Monday (25) in the journal Nature Geoscience.

Scientists have been trying for decades to predict the fate of life on Earth. Astronomers expect our Sun to grow brighter and, in about 7.6 billion years, could swallow the Earth.

But life probably won’t last that long. As the Sun throws more energy at the planet, Earth’s atmosphere will heat up, causing more water to evaporate from the oceans and continents. Water vapor is a powerful greenhouse gas, and so it will trap even more heat. In 2 billion years, it could become hot enough to evaporate the oceans.

In 2020, Farnsworth turned his attention to Earth’s future as a way to distract himself from the pandemic. He came across a study that predicts how continents will move around the planet in the distant future.

Throughout Earth’s history, its landmasses have collided to form supercontinents, which later broke apart. The last supercontinent, Pangea, existed from 330 million to 170 million years ago. The study predicted that a new supercontinent — called Ultimate Pangea — will form along the equator 250 million years from now.

In his early research, Farnsworth built models of the ancient Earth to reconstruct past climates. But he found it interesting to use his models to see what life would be like in Ultimate Pangea. The mood he ended up in surprised him.

“This world was very hot,” he said.

Farnsworth recruited Christopher Scotese, a retired geophysicist from the University of Texas who had created the Ultimate Pangea model, and other experts to run more detailed simulations of that distant future, tracking the atmosphere moving over the oceans, the supercontinent and its mountains.

“They did a lot, which really impressed me,” said Hannah Davis, an earth systems scientist at the German Geosciences Research Center GFZ, who was not involved in the research.

Under a range of possible geological and atmospheric conditions, researchers have found that Ultimate Pangea will be much hotter than today’s continents. One of the reasons for this drastic change is the sun. Every 110 million years, the energy released by the sun increases by 1%.

But the supercontinent will make things worse. For one, the land warms faster than the ocean. With the continents pushed into a single giant landmass, there will be a vast interior where temperatures can skyrocket.

Pangea Última will also influence the climate thanks to its topography, which will include vast expanses of flat land far from the ocean. On today’s Earth, rainwater and carbon dioxide react with minerals on the sides of mountains and hills, which are then washed out to sea and fall to the sea floor. The result is that carbon dioxide is gradually removed from the atmosphere. But when Earth becomes home to Ultimate Pangea, that conveyor belt will slow down.

If Pangea Ultima behaves like previous supercontinents, it will become dotted with volcanoes that spew carbon dioxide, the model found. Thanks to the turbulent movements of molten rocks deep in the Earth, volcanoes can release huge bursts of carbon dioxide for thousands of years — bursts of greenhouse gases that will cause temperatures to rise.

Currently, humans are warming the planet by releasing more than 40 billion tons of carbon from fossil fuels each year. If global warming continues unchecked, biologists fear it will lead to the extinction of several species, while people will be unable to survive the heat and humidity in large areas of the planet.

In Ultimate Pangea, Farnsworth and his colleagues concluded that things are likely to get much worse for mammals like us. Researchers found that almost all of Ultimate Pangea could easily become too hot for any mammals to survive. They could disappear in a mass extinction.

Farnsworth admitted that some mammals could survive in refuges on the shores of Ultimate Pangea. “Some areas on the northern and southern fringes may be habitable,” he said.

Even so, he was confident that mammals would lose the dominance they had enjoyed for the past 65 million years. They could be replaced by cold-blooded reptiles that could tolerate heat.

Wolfgang Kiessling, a climate scientist at the University of Erlangen-Nuremberg in Germany who was not involved in the study, said the model did not take into account a factor that could mean a lot for the survival of mammals: the gradual decrease in heat escaping from the environment. interior of the Earth. This decrease could lead to fewer volcanic eruptions and less carbon dioxide being released into the atmosphere.

“Mammals may survive a little longer than has been modeled,” he said — perhaps 200 million years, give or take.