Glacial melting on the Tibetan plateau could be the source of new pandemics

Earth’s glaciers are a storehouse for more than water. They also contain a plethora of frozen microbes that appeared thousands of years ago. If the planet’s glaciers melted completely, as climate change models suggest, some of these frozen microbes could revive and escape into the air, water and soil, possibly leading to the next global pandemic. .

The impact of these tiny invaders on established ecosystems and human beings would be unknown, and that’s why scientists are doing their best to assess all potential scenarios, including those that might fall into the “worst case” category. , like the one just identified following a recently completed four-year study in China.

As reported in the review Natural biotechnology , Chinese geneticists from Lanzhou University have studied microbial life forms found trapped in the 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 on Earth.

In particular, more than 80% of these microbes bear little or no resemblance to currently existing microorganisms. If humans are eventually exposed to it – a distinct possibility if current global warming leads to massive glacial melt – the results would be unpredictable at best and catastrophic at worst. A potentially worrying result could be the release into the environment of novel diseases transmitted by toxic microorganisms, which could eventually lead to a series of new global pandemics of undetermined severity.

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 span the Tibetan Plateau, a high-altitude glacial landscape in East Asia located in the northern shadow of the Himalayan mountain range.

The researchers knew that these ice cores would be teeming with microbes in various stages of suspended animation. But they had no idea how many new lifeforms they were destined to discover, and that number shocked even the most optimistic members of the group.

Chinese geneticists were able to recover DNA samples from nearly 1,000 different species, most of which were bacteria, but also archaea, algae and fungi. The high number of species detected and their genetic diversity were both unforeseen, as living and maintaining biological integrity inside a huge frozen block of ice proved very difficult for even the most difficult microorganisms. resistant.

“Despite extreme environmental conditions, such as low temperatures, high levels of solar radiation, periodic freeze-thaw cycles, and nutrient limitation, glacier surfaces support a wide range of life,” wrote the authors of the study in their Natural biotechnology article.

Some of the most illuminating and disturbing information gathered during the genetic analysis of microbes involves the presence of molecules called “virulence factors”. These are molecules that allow bacteria to invade and colonize human or animal hosts, giving dangerous bacteria the ability to do a lot of damage to their victims at the cellular level. An astonishing 47% of these virulence factors had never been observed before, meaning there is great uncertainty about the nature and severity of any disease that may result from bacterial infections that they promote.

In addition to virulence factors, Chinese geneticists have also discovered more than 25 million protein-coding genes in microbes, some of which may very well influence a bacterium’s ability to cause damage when it lodges in the environment. interior of biological organisms.

“Pathogens trapped in ice could lead to local epidemics and even pandemics,” the authors wrote, imagining a scenario where runoff from melting ice could release them into the environment in torrential quantities.

Some scientists believe that these microbes would struggle to survive if they were suddenly thawed and released. But even if they expired in the water, air and earth of their post-glacial environment, they could still pose a danger. If they manage to stay alive for a little while, the escaping pathogenic bacteria might be able to swap significant sections of their genetic material with other bacteria, which could pull the existing bacteria in different directions. unprecedented evolution. Previously harmless microbes could suddenly become dangerous to the health of people and animals, as many species would have no defense against bacteria that had never harmed them in the past.

This particular study did not focus on viruses. But they have also been found, surviving and intact, inside ice core samples.

In January 2020, another team of scientists recovered 33 different groups of viruses from a Tibetan glacier core sample. Worryingly, 28 of these clusters had never been seen before, meaning that modern humans have never been exposed to them (and therefore would have no immunity to their effects if exposed to them in close quarters). coming).

This particular result was obtained on a study that only included one glacier, suggesting that hundreds or thousands of additional viruses could be lurking inside the Tibetan Plateau’s ice cover.

Are we facing a future filled with disease?

Could the Tibetan plateau really be a source of future global pandemics?

Despite the remoteness of the plateau, runoff from this frigid region has access to a number of important waterways, including the Yangtze, Yellow, and Ganges rivers. These fast-flowing rivers supply fresh water to China and India, home to 40% 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 on their genetic material, epidemics would be possible and possibly probable.

But the situation on the Tibetan Plateau is just the tip of the iceberg, both figuratively and literally. There are over 20,000 glaciers on Earth that cover about 10% of the planet’s landmass, and if a massive melt occurred, the microbial communities released at each glacier site would vary in their characteristics and identities.

Studies have shown that the world’s glaciers are indeed melting slowly. If this trend continues, hundreds of thousands of new microbial species could eventually be released into the terrestrial environment. If only a small percentage of the most dangerous survive (whether they may or may not is still an open question), there could be a frightening amount of new pandemics in the planet’s future.

Top image: A yak grazes in the grasslands below a breathtaking glacier in the Himalayas. Source: helivideo /Adobe Stock

By Nathan Falde

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