About 250 million years have passed since reptiles evolved into mammals . Now, a team of scientists predicts that mammals may only have 250 million years left to survive.
The researchers built a virtual simulation of the future world, similar to models that predict human-caused global warming over the next century. The new study uses data on the movement of Earth's continents, as well as fluctuations in the chemical composition of the atmosphere, to make predictions even further into the future.
“Alexander Farnsworth, a paleoclimate scientist at the University of Bristol who led the team, said" the Earth could be so hot that no mammal, including us humans, could survive on land. The researchers found that the climate would become unviable because of three factors: a brighter sun, changes in continental geography and increases in carbon dioxide.
"It's a fatal triple whammy," Farnsworth said. He and his colleagues published their findings on Monday in the journal Nature Geoscience .
For decades, scientists have been trying to predict the fate of life on Earth. Astronomers predict that our sun will become increasingly brighter and engulf the Earth in about 7.6 billion years .
But life may not last that long. As the Sun projects more energy toward Earth, Earth's atmosphere will heat up, causing more water to evaporate from oceans and continents. Water vapor is a potent greenhouse gas and therefore absorbs more heat. The sun may become hot enough to evaporate the oceans in 2 billion years.
In 2020, Farnsworth turned his attention to the future of the planet as a way to distract himself from the pandemic. He came across a study predicting how land would move around the Earth in the distant future.
Over the course of Earth's history, continental plates collided to form supercontinents and then broke apart. The last supercontinent - Pangea - existed between 330 million and 170 million years ago. The study predicts that in 250 million years, a new supercontinent, called Pangea Ultima, will form along the equator.
After preliminary research, Farnsworth built a model of the ancient Earth to reconstruct past climates. But he thought it would be interesting to use his model to see what life would be like on Ultimate Pangea. The climate at the time surprised him.
He said: "The world is quite warm and comfortable."
Farnsworth enlisted retired University of Texas geophysicist Christopher Scoteser and other experts to conduct more detailed simulations far into the future, tracking atmospheric movements over oceans, supercontinents and their mountain ranges. Scotesser created the ultimate model of Pangea.
"I'm really impressed with how much work they've done," said Hannah Davis, an Earth systems scientist at the German Geological Research Center in Germany.
The researchers found that under a range of possible geological and atmospheric conditions, Pangea Ultima would have been much hotter than today's continent. One of the causes of this drastic change is the sun. Every (110 million years) the energy released by the sun increases by 1%...
But a supercontinent would make things worse. First, land heats up faster than oceans. As the continents are squeezed into one giant landmass, creating a vast interior, temperatures will soar.
Pangea Ultima will also have an impact on the climate due to its topography, which includes large stretches of flat land far from the ocean. On Earth today, rainwater and carbon dioxide react with minerals on the sides of mountains and hills and are carried to the oceans, where they fall to the bottom of the ocean. The result is that carbon dioxide is steadily pumped out of the atmosphere. But when Ultimate Pangea dominates, the conveyor belt will slow down.
The model found that if Pangea Ultima was like previous supercontinents, it would be riddled with volcanoes spewing carbon dioxide. Due to the violent movement of molten rock deep within the Earth, these volcanoes could release large amounts of carbon dioxide over thousands of years - bursts of the greenhouse gas that would drastically increase temperatures.
Currently, humans release more than 40 billion tons of carbon from fossil fuels every year , causing the earth to continue to heat up. Biologists fear that if global warming continues, many species will become extinct and humans will be unable to survive in the heat and humidity of large swathes of the planet .
Farnsworth and his colleagues concluded that things could have gotten worse for mammals like us in Pangea Ultima. Researchers have found that nearly all of Pangea Ultima could easily have become too hot for all mammals to survive. They may disappear in a mass extinction.
Farnsworth believes that a few mammals might eke out a living in the refuges on the edge of Pangea. "Some areas on the northern and southern edges may still be viable," he said.
Even so, he believes mammals will lose the dominance they have had for the past 65 million years. They may have been replaced by cold-blooded reptiles that could tolerate heat.
Wolfgang Kiesling, a climate scientist at the University of Erlangen-Nuremberg in Germany, said the model did not take into account a factor that could be significant for the survival of mammals: the gradual reduction in heat escaping from the Earth's interior. This decline could lead to fewer volcanic eruptions and less carbon dioxide emissions in the atmosphere.
"Mammals may survive a little longer than models predict," he said. Maybe 200 million years, roughly in that range.
Eric Wolf, a planetary climate scientist at the “(University of Colorado)" said the research may one day help us discover life on other planets.... As scientists begin to use powerful space telescopes to observe other planets in the solar system, they may be able to measure the layout of the planets' continents and infer what kind of life might exist there.
"We're trying to prepare for the many worlds we're going to see," Wolf said.