Study finds that mammals’ time on Earth may have already ended: NPR

New study in the magazine Natural earth sciences He predicts that 250 million years from now, the supercontinent forming around the equator will be too hot for mammals to survive.

Jean-Philippe Ksiazek/AFP via Getty Images

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Jean-Philippe Ksiazek/AFP via Getty Images

New study in the magazine Natural earth sciences He predicts that 250 million years from now, the supercontinent forming around the equator will be too hot for mammals to survive.

Jean-Philippe Ksiazek/AFP via Getty Images

You can say this about mammals: we’ve done well.

For the 250 million years since the first mammals diverged from reptiles and birds, we, the warm-blooded vertebrates, have dominated Earth, with rodents, humans, ungulates, and whales inhabiting almost every inch of the planet.

But the end of this era may come much sooner than traditionally thought, he points out New study Published this week in the magazine Natural earth sciences.

Scientists have long believed that life on Earth would continue until the planet entered a phase of “runaway global warming” — a state in which water vapor and other greenhouse gases in the atmosphere become so dense that heat can no longer escape the surface and the oceans boil. Like the planet Venus. That’s 2 or 3 billion years away.

The study concluded that mammals would face problems much sooner because of our limited ability to withstand heat. Our mechanisms for avoiding overheating – such as sweat, circulatory systems and the ability to physically move to cooler environments – can only go so far, and evolution can only move so quickly, said Alexander Farnsworth, a climate researcher at the University of Bristol and lead author. . On studying.

Ultimately, “Earth could reach a tipping point that makes it uninhabitable for mammalian life,” the researchers wrote.

The study places the end date for mammals at about 250 million years from now, roughly the same time since mammals first appeared.

It is difficult to predict what the planet will look like long from now; By comparison, modern humans have only been around for about 50,000 years and have changed the planet dramatically in that time.

However, Farnsworth and his colleagues describe three main factors that will lead to higher temperatures on Earth.

Grand: The supercontinent of the future. Throughout Earth’s history, the continents have gone through a cycle of coming together into supercontinents, then moving apart again into separate continents as we see today. Projections indicate that the next cycle will combine our current continents into a supercontinent, called Pangea Ultima, centered along the equator.

“Instead of having continents spread out around the world, they all now live in mostly the tropics. And of course, we know that the tropics are a very hot and humid place to live. So this will really have a big impact,” Farnsworth said.

The study says that in addition, there will be an increase in volcanic activity. Historically, supercontinents have coincided with an increase in volcanic activity, releasing more carbon dioxide into the atmosphere, perhaps double the current amount, researchers expect.

Meanwhile, as the Sun ages, it will emit more energy — an estimated 1% more every 100 million years — adding more heat to the equation.

Most of the supercontinent will have average monthly temperatures exceeding “40, 50 or even 60 degrees Celsius” — the equivalent of 104, 122 or 140 degrees Fahrenheit, Farnsworth said.

“It wouldn’t be a very happy place for most species to live,” he said.

Only 8% of Earth may be habitable for mammals, according to the study. Competition will be intense for those plots of habitable land, which lie mostly along the edges of what are now Canada, Russia and Chile. Reptiles could re-emerge as the dominant species, or birds could win.

He said the best hope for mammals to survive during the Pangea Ultima era on Earth could look like the North African gerbil – a small rodent that thrives in the harsh conditions of the Sahara Desert. “It doesn’t need a lot of moisture, a lot of water, or a lot of food,” he said. “Who knows? Maybe it will radiate outward and mammals will evolve from these lineages into something new.”