In millions of years’ time, a new supercontinent will form when all of our existing continents converge. This, according to a new study, will have a series of catastrophic impacts that will make Earth inhospitable to land-based mammals and will likely lead to a mass extinction.
No more mammals?
Greenhouse gas emissions caused by human activity are pushing our climate to extremes that have not been experienced in millions of years. This is already having a devastating impact on ecosystems across the world, but despite this, it is still not clear whether such drastic changes will ever reach a tipping point where mammals can no longer survive.
According to some research, current warming trends will raise global temperatures to such an extent that some areas of the world, such as regions of Africa, Australia, Europe, and South Asia will eventually become inhospitable to mammal life. However, even with the combustion of all available fossil fuels in the distant future, most of the world’s surface will still be suitable for some mammals to survive on.
Outside of the climate crisis, there is also the inevitable point where the Earth will leave the Sun’s habitable zone, which will ultimately destroy all life on the planet as it experiences a runaway greenhouse effect.
Alas, this is not a cheery topic to be sure, but while this latter situation will not occur for billions of years, new research conducted by an international team of scientists has even worse news – mammalian life could be destroyed far sooner than this because of long-term processes linked to tectonic plates.
The supercontinent that will end it all
As we know, the Earth’s surface is not static. Although it changes at the same rate that human fingernails grow, the continents are shifting all the time. It is estimated that in about 250 million years, most of the existing continents will collide to form a supercontinent called “Pangea Ultima”. Unfortunately, the formation of this new supercontinent will likely usher in significant global changes that will make the planet inhospitable to mammals.
The geological record shows that, over the last 3.5 billion years, there were significant swings in atmospheric PCO2, partial pressure of carbon dioxide, throughout the stages of continental assembly, tenure, and break-up. PCO2 is usually used to measure CO2 within blood, but it is also used in meteorology and climate science to describe the fractional pressure of the gas as a function of its concentration in the atmosphere.
Essentially, whenever supercontinents form and eventually break up, they cause natural cycles of heating and cooling that change the amount of PCO2 in the atmosphere. However, the formation of Pangea Ultima will likely coincide with increased solar activity from the Sun. This will see it emit around 2.5 percent more energy compared to today, which, coupled with the continent’s tectonic activity, especially through volcanic emissions, will lead to an increase in atmospheric PCO2.
“The formation and decay of [this supercontinent] will limit and, given a much greater source-to-sink ratio of pCO2, ultimately end terrestrial mammalian habitability on Earth by exceeding their warm thermal tolerances, billions of years earlier than previously hypothesized”, the researchers explain in their study.
Inevitably, they claim, the changes in both plate tectonics and the increased solar energy will create feedback in the climate that will raise the global mean annual temperature (GMAT). The impacts of this combination will likely lead to massive hyperthermal events akin to the Permian–Triassic event, the largest and most severe known extinction event the Earth has ever experienced.
“Today, critical heat stress measures are rarely exceeded on land and, if so, only for short time scales (hours or days). If only the geography was to change, critical heat stress is not exceeded but does drive the climate towards critical thresholds”, the authors add.
“Combined with a future increase in [solar energy], large regions of the supercontinent breach these critical thresholds for periods of [30 days or more].”
According to their models, the temperature changes in many regions will mean that only highly specialized migratory mammals would be able to compete in such environments. But even for these rare few, the continental conditions – such as extensive desserts – may make such migratory strategies ineffective.
Even burrowing species that can avoid surface heat above ground only show a small increase in survivability.
The results from these models are pretty damning and understandably heavy to read. It is worth remembering that we can still take action to limit the impacts of human-led climate change for generations of the near future. Still, if you’re in need of a quick palate cleanser, have a look at this adorable discovery that will cheer anyone up.
The study is published in Nature Geoscience.
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