https://www.earth.com/news/scientists-predict-how-and-when-humans-and-mammals-will-face-extinction/
By Eric Ralls
A new study suggests that extreme temperatures could lead to a mass extinction event — the first since the dinosaurs died out — that would ultimately end the reign of humans and mammals on Earth.
Dr. Alexander Farnsworth, a Senior Research Associate at the University of Bristol, led the research that paints a grim picture of our planet’s distant future.
Pangea Ultima — future supercontinent
Scientists believe that Earth’s continents are slowly drifting and will eventually come together to form a single massive landmass, called Pangea Ultima.
This supercontinent would drastically change the planet’s climate.
The study, published in Nature Geoscience, uses supercomputer climate models to show how this new configuration could create an environment that’s too hot and dry for most life forms.
Triple threat to life on Earth
So, what’s causing this extreme heat that results in the extinction of humans?
“The newly-emerged supercontinent would effectively create a triple whammy, comprising the continentality effect, hotter sun and more CO₂ in the atmosphere, of increasing heat for much of the planet,” Dr. Farnsworth explained.
First, the formation of the supercontinent would mean more land area far from the cooling effects of the ocean — a phenomenon known as the continentality effect.
Second, over millions of years, the sun will become brighter, emitting more energy and warming the Earth.
Third, increased volcanic activity due to tectonic movements would release more carbon dioxide into the atmosphere, trapping more heat.
“Widespread temperatures of between 40 to 50° Celsius (104 to 122° Fahrenheit), and even greater daily extremes, compounded by high levels of humidity would ultimately seal our fate,” Dr. Farnsworth added.
“Humans — along with many other species — would expire due to their inability to shed this heat through sweat, cooling their bodies.”
Mammals’ heat limitations
Mammals have always been adaptable, surviving various climate extremes throughout history. We’ve evolved features like fur to keep warm and the ability to hibernate during cold spells.
However, our upper temperature tolerance hasn’t changed much. Prolonged exposure to excessive heat is much harder for mammals to handle.
The study suggests that only about 8% to 16% of the land on the new supercontinent would be habitable for mammals.
With most of the planet facing extreme heat and dryness, finding food and water would become nearly impossible.
Current climate action and extinction of humans
While this scenario is millions of years away, the researchers stress that we shouldn’t lose sight of the current climate crisis.
“It is vitally important not to lose sight of our current Climate Crisis, which is a result of human emissions of greenhouse gases,” urged Co-author Dr. Eunice Lo, Research Fellow in Climate Change and Health at the University of Bristol.
“While we are predicting an uninhabitable planet in 250 million years, today we are already experiencing extreme heat that is detrimental to human health. This is why it is crucial to reach net-zero emissions as soon as possible.”
CO₂ levels and tectonic shifts
To estimate future carbon dioxide levels, the team used models of tectonic plate movement and ocean chemistry.
They predict that CO₂ levels could rise from around 400 parts per million today to more than 600 ppm in the future.
“We think CO₂ could rise from around 400 parts per million (ppm) today to more than 600 ppm many millions of years in the future,” noted Professor Benjamin Mills at the University of Leeds.
Of course, this assumes that humans will stop burning fossil fuels, otherwise we will see those numbers much, much sooner.”
“The outlook in the distant future appears very bleak. Carbon dioxide levels could be double current levels,” Dr. Farnsworth added.
“With the sun also anticipated to emit about 2.5% more radiation and the supercontinent being located primarily in the hot, humid tropics, much of the planet could be facing temperatures of between 40 to 70°C (104 to 158°F).”
Implications beyond Earth
This research doesn’t just tell us about Earth’s future; it also has implications for the search for life on other planets.
“This work also highlights that a world within the so-called ‘habitable zone‘ of a solar system may not be the most hospitable for humans depending on whether the continents are dispersed, as we have today, or in one large supercontinent,” Dr. Farnsworth concluded.
Understanding how continental layouts affect climate can help scientists assess the habitability of exoplanets — planets outside our solar system. Could other worlds be facing similar challenges?
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The full study was published in the journal Nature Geoscience.
