Over the past 500 million years, our planet has experienced a total of five mass extinctions. One of these, the Permian-Triassic mass extinction, led to the death of approximately 90% of Earth’s species. Many of these events coincided with the formation of a supercontinent, where Earth’s tectonic plates gradually came together and fused.

Scientists predict that the Earth’s continents will reunite within 250 million years and form a supercontinent called “Pangaea Ultima”. It will be centered over the equator and will be hot. Conditions in Pangea Ultima will be extremely unfavorable for most mammals to survive, according to new research I conducted with several colleagues from the University of Leeds and Northwestern University in the US.

The formation of this supercontinent would increase volcanic activity and the ancient sun would emit more radiation to the Earth. This would lead to extremely high land surface temperatures that would turn much of the continent into a vast, hot desert reminiscent of the desert planet Arrakis in the sci-fi epic Dune. During the hottest months of the year, temperatures can exceed 40°C across much of the supercontinent, and temperatures can exceed 50°C in many areas.

it will be hot

Today, mammals can survive on approximately two-thirds of the Earth’s surface. However, after regrouping the continents, other things being equal, our simulations showed that the mean annual land temperature would increase from the pre-industrial average (about 5°C) to about 24°C. This change would reduce Earth’s habitable area to only 54%.

The main reason for this increase in temperature is the projected location of Pangea Ultima, whose center will be at the equator. However, various other factors will also contribute to this warming, such as differences in elevation above ground level (higher altitudes tend to be colder), the absence of ice sheets, and changes in vegetation cover and abundance.

Our predictions also show that when Pangea Ultima forms, the sun will be 2.5% brighter than it is now. This increased solar intensity would increase the average land temperature on Earth to approximately 25°C, leaving only a quarter of the planet’s surface habitable.

One of the uncertainties lies in atmospheric CO2 levels during the formation of Pangea Ultima. Our simulations show that CO2 concentrations could be as high as 613 parts per million (ppm), compared to the typical background level of 420 parts per million today. This increase in CO2 will cause the average land surface temperature to fluctuate between 30°C and 35°C, reducing Earth’s habitability by 8-16%. Considering daytime maximum temperatures and extreme weather events, there is the potential for temperatures to exceed 60°C in some regions.

hostile conditions

The key to the success of mammals since the dinosaurs has been their ability to adapt. They have the ability to regulate body temperature regardless of changes in the external environment.

For example, while humans cool down by sweating in hot weather, dogs use breathing to dissipate heat. Elephants radiate heat through their large ears.

However, when the surrounding air is warmer than skin temperature, the body tries to dissipate heat, resulting in overheating. Prolonged exposure to such conditions can lead to heatstroke, causing critical organs such as the brain to swell.

Mammals can only withstand a certain temperature range. The situation becomes dangerous when the dry-bulb temperature (measured with a standard thermometer) exceeds 40°C or the wet-bulb temperature exceeds 35°C (the lower limit affected by high humidity). Recent research even suggests that the wet-bulb temperature limit for humans and most mammals may be as low as 31.5°C. Exposure to these temperatures for just six hours, even in the shade, when wet, and with a fan, can lead to death.

Some mammals have even lower temperature thresholds. For example, the critical wet bulb temperature threshold for North American moose is 17°C in calm conditions and 24°C in windy conditions.

Do mammals have a chance?

Mammals have experienced warm periods in the past, such as the Paleocene-Eocene Thermal Maximum (PETM), about 50 million years ago, when the Earth’s surface temperature increased by about 5°C. However, there are some important differences in the formation of Pangea Ultima that should be considered.

First, the PETM was relatively short, lasting approximately 100,000 years. After that the temperature gradually dropped to a more livable level. In contrast, Pangea Ultima is predicted to last tens of millions of years or longer before breaking apart.

Second, during the PETM the continents were arranged in a way that allowed mammals to more easily move to cooler regions closer to the poles to escape extreme heat. In Pangea Ultima, most of the planet will be concentrated in the tropics, and vast impassable deserts will cover most of the supercontinent. This will make it difficult for mammals to travel long distances to find cooler places.

Tectonics have played and will continue to play a fundamental role in shaping the evolution of life on our planet. Everyone wonders which way of life will become dominant if mammals die. But mammals will have a good run. Source