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The Countdown to Extinction for Mankind and Mammals

The forthcoming mass extinction could be instigated by extreme heat, with humans possibly counted among its victims. According to recent research published in the journal Nature Geoscience, cutting-edge climate models run on supercomputers project a dire future. Over the course of the next 250 million years, the Earth's temperature is predicted to soar to levels incompatible with the survival of most mammal species. This grim outlook is further intensified by the anticipated formation of a new supercontinent near the equator.
In this bleak scenario, humanity also faces the peril of extinction. Nevertheless, our prospects for survival appear somewhat more favorable compared to other species, thanks to our technological advancements.
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Alexander Farnsworth, the lead author of the paper and a senior research associate at the University of Bristol in the U.K., explained, "When we solely rely on humans' innate ability to endure extreme heat without any technological assistance, we encounter several critical heat stress thresholds."
He continued, "Exposure to wet-bulb temperatures, which accounts for both heat and moisture, exceeding 35 degrees Celsius (95 degrees Fahrenheit) for more than six hours could prove fatal. Recent research even suggests this threshold might be lower, around 32 degrees Celsius (89.6 degrees Fahrenheit). This assessment considers conditions of complete inactivity, ample shade, absence of clothing, and access to unlimited drinking water. Similarly, dry-bulb temperatures, the measurements you obtain with a thermometer, surpassing 40 degrees Celsius (104 degrees Fahrenheit) along with low humidity over an extended period also pose a lethal threat."
Farnsworth added, "When we factor in technology, such as the ability to construct environmentally controlled shelters equipped with air conditioning, human survival becomes feasible. However, we would likely need to create additional facilities to support food production under these extreme conditions."
Image shows the warmest month average temperature (degrees Celsius) for Earth and the projected supercontinent (Pangea Ultima) in 250 million years, when it would be difficult for almost any mammals to survive. University of Bristol
Image shows the warmest month average temperature (degrees Celsius) for Earth and the projected supercontinent (Pangea Ultima) in 250 million years, when it would be difficult for almost any mammals to survive. University of Bristol


These extreme temperature fluctuations, potentially ranging from 104 to 158 degrees Fahrenheit, are forecasted to occur due to elevated levels of carbon dioxide in the atmosphere. This increase is primarily attributed to tectonic activity, which triggers volcanic eruptions, as well as a 2.5 percent rise in solar radiation emitted by the sun itself.
"In our study, we illustrate that global temperatures could escalate to be approximately 10-15 degrees Celsius (18-27 degrees Fahrenheit) higher than current levels. Moreover, land temperatures alone could surge to an average of 25-30 degrees Celsius (45-54 degrees Fahrenheit) warmer than today," noted Farnsworth.
The authors of the study anticipate that this escalating heat problem will reach a critical point with the emergence of the next supercontinent, Pangea Ultima. During this period, only 8 to 16 percent of the land is expected to be habitable for mammals. This limitation is due to the supercontinent's location around the equator, where temperatures are at their most extreme, compounded by the release of CO2 resulting from tectonic activity and the shifting of continents.
Farnsworth elaborated, "We've identified three primary factors leading to this extreme climatic state that would render Earth inhospitable in 250 million years. Firstly, even without altering carbon dioxide levels in the atmosphere (maintaining pre-industrial revolution levels) and keeping the sun's brightness (i.e., the amount of energy the sun emits) at present-day levels, the mere rearrangement of continents into a supercontinent significantly elevates land surface temperatures. This is largely because most of the land surface is concentrated in the tropics under this scenario."
"Secondly, the sun is predicted to be approximately 2.5 percent brighter in 250 million years, contributing additional energy to Earth and further elevating global temperatures. Lastly, the tectonic dynamics of this supercontinent are expected to generate increased volcanic degassing, releasing around 600 ppm of CO2 into the atmosphere as the most likely outcome," Farnsworth explained.
The image shows the geography of today’s Earth and the projected geography of Earth in 250 million years, when all the continents converge into one supercontinent (Pangea Ultima). University of Bristol
The image shows the geography of today’s Earth and the projected geography of Earth in 250 million years, when all the continents converge into one supercontinent (Pangea Ultima). University of Bristol


Mammals are particularly vulnerable to these rising temperatures, as our evolutionary history has equipped us to handle cold conditions much more effectively than extreme heat. The study highlights that over time, mammals have adapted to tolerate lower temperatures, but our capacity to endure higher temperatures has remained relatively constant, making us susceptible to extreme heat events.
Explaining this vulnerability, Farnsworth stated, "Mammals maintain relatively stable internal body temperatures through thermoregulation, typically around 37 degrees Celsius (98.6 degrees Fahrenheit) for humans. When exposed to heat, we cool down by sweating. This is our body's mechanism to dissipate excess heat. For this cooling process to be effective, the surrounding air must be cooler than our skin, which, in turn, should be cooler than our core body temperature."
He continued, "If the environmental temperature surpasses the skin's temperature, it becomes difficult to release metabolic heat, potentially leading to dangerous overheating. The severity and duration of this heat stress can result in conditions like heatstroke, causing swelling in vital organs such as the brain, leading to permanent damage."
Furthermore, the study underscores that extreme heat will also devastate the habitats upon which many mammals rely, including their food sources, exacerbating the threat to their survival.
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The implications of soaring temperatures are not limited to mammals alone. As the study emphasizes, plants, in general, are not well-suited to temperatures exceeding 40 degrees Celsius (104 degrees Fahrenheit), with some exceptions. Unfortunately, much of the continent could experience temperatures surpassing this threshold. Since plants form the foundation of the food pyramid, their decline over extensive areas could place significant stress on other species, including insects that rely on them for sustenance. This, in turn, would affect higher trophic level species that depend on insects as a food source.
While the study primarily focused on mammals, it is challenging to provide a comprehensive assessment of how this climatic shift might impact other classes of animals. However, it is reasonable to infer that such a world would be inhospitable for many species across the board. The interconnectedness of ecosystems means that disruptions at one level can have cascading effects throughout the entire ecosystem, potentially imperiling a wide range of organisms.
  • Sarah Chabane

    42 w

    This is very scary....

    8
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