The Slow Changes in Earth’s Geography
Our planet’s surface is not frozen in time. Over hundreds of millions of years, continents drift, collide, and reassemble to form vast supercontinents that reshape Earth’s topography and atmosphere. These geological cycles unfold on timescales that far exceed human history, yet leave lasting marks on the climate, ocean circulation, and the survival of species.
The next of these major transformations could have consequences on an unprecedented scale. Although it lies several hundred million years in the future, the formation of Earth’s next supercontinent is expected to create environmental extremes never before seen, with profound implications for life as we know it today.
A recent peer-reviewed study, published in the journal Nature Geoscience, examines what such a world might look like. By combining advanced climate modeling with tectonic and atmospheric projections, the researchers present one of the most detailed predictions to date regarding Earth’s long-term future. Their findings outline a scenario in which rising temperatures and declining habitability converge across most of the landmass.
The Birth of Pangea Ultima and Extreme Warming
The central premise of this research is based on the formation of Pangea Ultima, a future supercontinent expected to emerge in about 250 million years. As the Earth’s tectonic plates continue to shift, the current continents are expected to converge to form a single massive landmass stretching across the equator.
This new configuration would fundamentally alter the planet’s energy balance. With less ocean surface area to moderate heat and a larger proportion of land concentrated in the tropics, global temperatures would rise sharply. The study’s authors modeled these conditions using the HadCM3L general circulation model, incorporating a 2.5 percent increase in solar radiation, which corresponds to astrophysical estimates for this period.
The simulations show that global average land temperatures would rise by 30 degrees Celsius compared to pre-industrial levels. On the future supercontinent, average temperatures would range from 24.5 degrees Celsius to 35.1 degrees Celsius, with regional peaks climbing significantly higher. The researchers identify three key factors behind this result, which exceeds the physiological limits of many mammals: the continentality effect, increased solar irradiance, and high concentrations of atmospheric carbon dioxide (CO₂), which are projected to rise due to intensified volcanic activity during continental convergence.
A Critical Form of Thermal Stress for the Animal Kingdom
One of the study’s most notable findings concerns heat stress thresholds. Mammals regulate their body temperature through evaporative cooling, such as sweating or panting, but this mechanism fails when heat and humidity exceed a certain limit. The research team uses indicators such as the wet-bulb temperature and the Humidex index to estimate survival chances in various regions.
Wet-bulb temperatures above 35 degrees Celsius—the threshold at which humans can no longer cool themselves effectively—are expected to occur on a large scale. Humidex values, used to assess the combined impact of temperature and humidity, also exceed levels considered dangerous. Even under moderate CO₂ scenarios set at 560 ppm, only 16 percent of the supercontinent’s land area would remain within habitable thresholds. At higher CO₂ levels reaching 1,120 ppm, this share drops to just 8 percent.
"Widespread temperatures ranging from 40 to 50 degrees Celsius (104 to 122 degrees Fahrenheit), and even higher daily extremes, exacerbated by high humidity levels, would ultimately seal our fate," said Dr. Alexander Farnsworth, lead author and senior research associate at the University of Bristol, who coordinated the modeling. In addition to direct heat stress, aridity would reduce access to water and vegetation, thereby limiting food availability. Potential migration across vast desert interiors would become increasingly difficult, while refuges at high latitudes would offer only very limited relief.
Volcanism, the carbon cycle, and historical precedents
Past extinction events have often followed sharp increases in atmospheric CO2. Researchers modeled long-term carbon levels using the SCION biogeochemical framework, taking into account tectonic plate movements, volcanic degassing, and changes in continental weathering. The study estimates that future background CO₂ levels will range from 410 to 816 ppm, with an average of 621 ppm, resulting in a sustained greenhouse climate even without additional anthropogenic emissions.
The reduced efficiency of silicate weathering—which acts as a natural CO₂ sink—on a dried-up supercontinent would further slow the removal of excess carbon from the atmosphere. Historical records provide highly relevant comparisons. The Late Permian extinction, which occurred approximately 252 million years ago, was marked by a temperature spike of about 10 degrees Celsius and the loss of more than 90 percent of marine species. Similar carbon and temperature dynamics are projected for the Pangea Ultima period.
As Earth.com’s report on the study points out, “with so much land becoming arid, the search for food and water would become daunting.” Conditions on Earth will likely exceed the thresholds of those distant eras. Even species equipped with adaptive strategies such as hibernation or burrowing would face increasing pressure, particularly as the loss of vegetation weakens ecosystems at all latitudes.
Rethinking the Concept of Habitability Beyond Our World
These numerous findings have direct implications for the study of exoplanets. Traditionally, planetary habitability is assessed based on the orbital distance from a star. The Earth’s own trajectory shows that habitability is by no means a fixed quantity; it can vary depending on internal dynamics such as continental layout and atmospheric chemistry.
“This work also highlights that a world located in the so-called ‘habitable zone’ of a solar system might not be the most hospitable for humans, depending on whether the continents are scattered, as they are today, or arranged into a single large supercontinent,” explained Dr. Farnsworth, as quoted in the journal Nature Geoscience.
Under conditions of high CO₂ levels and increased solar radiation, Earth itself would no longer meet the criteria of widely used astrophysical indices, such as the Earth Similarity Index (ESI), which takes into account mass, radius, temperature, and the ability to retain liquid water. The research team found that none of the projected scenarios for Pangea Ultima reach the ESI habitability threshold of 0.8, even though the planet remains well within its current orbital zone.
Source: dailygalaxy.com
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