Glacial Melt On Tibetan Plateau Could Be Source of New Pandemics
The Earth’s glaciers are a storehouse for more than just water. They also contain a plethora of frozen microbes that came into existence thousands of years ago. Should the planet’s glaciers melt completely, as climate change models suggest many ultimately will, some of these flash-frozen microbes could spring back to life and escape into the air, water, and soil, possibly leading to the world’s next pandemic.
The impact of these tiny invaders on established ecosystems and human beings would be unknown, and that is why scientists are doing their best to evaluate all potential scenarios, including those that might fall under the ‘worst case’ category—like one that has just been identified following a four-year study that was recently completed in China.
As reported in the journal Nature Biotechnology, Chinese geneticists from Lanzhou University have been studying microbial life forms found trapped in glaciers that currently cover the Tibetan Plateau. After completing their analysis, they were shocked to discover 968 new species and bacteria and other tiny life forms that had never been seen before anywhere on Earth.
Notably, more than 80 percent of these microbes show little or no resemblance to currently existing microorganisms. If human beings are eventually exposed to them—a distinct possibility if the current warming of the planet leads to massive glacial melt—the results would be unpredictable at best and catastrophic at worst. One potentially disturbing outcome could be the release into the environment of never-before-seen diseases carried by toxic microorganisms, which could conceivably lead to a string of new global pandemics of undeterminable severity.
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3D illustration of a colony of microbes. Source: Siarhei / Adobe Stock
Hiding in the Ice, Waiting for the Chance to Escape
Between 2016 and 2020, project scientists extracted core samples from 21 glaciers that cover the Tibetan Plateau, a frigid, high-altitude landscape in eastern Asia located in the northern shadows of the Himalayan Mountain range.
The researchers knew these ice cores would be teeming with microbes in various stages of suspended animation. But they had no idea how many new life forms they were destined to discover, and the number shocked even the most optimistic members of the group.
The Chinese geneticists were able to salvage DNA samples from nearly 1,000 different species, most of which were bacteria but also included archaea, algae, and fungi. The high number of species detected and their genetic diversity were both unanticipated, since living and maintaining biological integrity inside a huge frozen block of ice figured to be highly challenging for even the hardiest of microorganisms.
"Despite extreme environmental conditions, such as low temperatures, high levels of solar radiation, periodic freeze-thaw cycles and nutrient limitation, the surfaces of glaciers support a diverse array of life," the study authors wrote in their Nature Biotechnology article.
Some of the most enlightening and disturbing information collected during the genetic analysis of the microbes involves the presence of molecules known as ‘virulence factors.’ These are molecules that enable bacteria to invade and colonize human or animal hosts, giving dangerous bacteria the opportunity to do a lot of damage to their victims at the cellular level. A stunning 47 percent of these virulence factors had never been previously seen, which means there is great uncertainty about the nature and severity of any disease that might result from bacterial infections they would encourage.
In addition to the virulence factors, the Chinese genetic scientists also discovered more than 25 million protein-coding genes in the microbes, some of which could very well influence a bacteria’s capacity to cause damage when lodged inside biological organisms.
"Ice-entrapped pathogenic microbes could lead to local epidemics and even pandemics," the authors wrote, imagining a scenario where runoff from glacial melt could release them into the environment in torrential quantities.
Some scientists believe these microbes would have trouble surviving if suddenly thawed and released. But even if they expired in the water, air, and earth of their post-glacial environment, they could still present a danger. Should they manage to stay alive for just a little while, escaping pathogenic bacteria might be able to exchange significant sections of their genetic material with other bacteria, which could take existing bacteria off into unprecedented evolutionary directions. Previously harmless microbes could suddenly become hazardous to the health of people and animals, as many species would have no defense against bacteria that had never caused them any harm in the past.
This particular study did not focus on viruses. But they have also been found, surviving and intact, inside glacial core samples.
In January 2020, a different team of scientists recovered 33 different groups of viruses from a Tibetan glacier core sample. Ominously, 28 of these groups had never before been seen, meaning modern humans have had no previous exposure to them (and would therefore have no immunity to their effects should they be exposed to them in the near future).
This particular result was achieved on a study that included just one glacier, which suggests that hundreds or thousands more viruses might be lurking inside the Tibetan Plateau ice cover.
Are We Facing a Future Filled with Illness?
Could the Tibetan Plateau truly be a source for future global pandemics?
Despite the plateau’s remoteness, runoff from this frosty region does have access to a number of important waterways, including the Yangtze, Yellow, and Ganges Rivers. These high-volume rivers supply fresh water to China and India, home to 40 percent of the world’s population. Dangerous bacteria released from Tibetan glaciers would inevitably reach densely populated regions, and if they were able to survive the journey long enough to at least pass their genetic material on, disease outbreaks would be possible and perhaps likely.
But the situation on the Tibetan Plateau is just the tip of the iceberg, both figuratively and literally. There are more than 20,000 glaciers on Earth that cover approximately 10 percent of the planet’s landmass, and should massive melting occur microbial communities released at each glacial site would vary in their characteristics and identities.
Studies have shown that the world’s glaciers are indeed slowly melting. If that trend continues, hundreds of thousands of new microbial species could ultimately be released into Earth’s environment. If just a small percentage of the most dangerous ones survive (which they may or may not, that is still an open question), there could be a frightening quantity of new pandemics in the planet’s future.
Top image: A yak grazes in the meadows under a breath-taking glacier in the Himalayas. Source: helivideo / Adobe Stock
By Nathan Falde