You may feel that we all have enough to worry about, and thus have no need for the spectre of zombie-like reanimated bacteria or viruses in thawing permafrost that set off a story straight out of a sci-fi flick. Unfortunately, it's a looming reality thanks to climate change.
Luckily, scientists tell us that while it's high time we thought carefully about how we are going to manage the vast numbers of microbes being released along with equally vast quantities of melting ice and thawing permafrost as a result of global heating, there is no need to panic nor to sensationalize the issue.
When Salon spoke with microbiologist Luis Andrés Yarzábal, an associate professor at the Universidad Católica de Cuenca in Ecuador, he was indeed careful to avoid sensationalizing the problem. But he noted that we've been aware since the '80s of dramatic quantities of microbes found in even the most pristine of Antarctic ice sheets or on top of mountains, such as the Andean glaciers, and in permafrost. The host of life on ice includes bacteria, viruses, fungi, protozoa, even microscopic animals like nematodes, some dead and some alive in suspended animation.
Yarzábal actually started studying the microbiology of the Andean glaciers, beginning in Venezuela 17 years ago, because he and his team were interested in the biotechnological potential of cold-loving, or psychrophile, microorganisms.
"They can be used, for instance, for agricultural purposes, to improve agriculture in cold regions, in mountainous regions." But the country's glaciers melted, and as they did, it revealed huge numbers of pathogens in the melting ice. Some of these disease-causing bugs may be so old, human immune systems are totally naïve to them, which means unleashing them could infect millions, maybe even trigger another pandemic. The odds of such an event may be remote — we don't actually know how likely this all is — but we do know the likelihood isn't zero and it will increase as the world's ice retreats.
"Venezuela is now the first country in the modern world to have lost all its glaciers, and there were many, many pathogens," Yarzábal said. Some are very similar to modern human pathogens. From bioprospecting beneficial microbes, he was now forced to consider less cheery possibilities. After all, Venezuela's lost glaciers were far from the only ones releasing water that has been frozen for tens or hundreds of thousands of years. Newly published research in Nature suggests that between 2000 and 2023, the world's glaciers lost some 275 gigatonnes, give or take, in mass annually, with the rate of melting increasing substantially more recently.
Disrupting the ecological equilibrium always has the potential to cause hazards to human health directly.
"The rate at which we lost ice during these 23 years is approximately the amount of water contained in four Olympic pools, per second. So that's a lot of microbes that will disperse around the ecosystems, aquatic and terrestrial ecosystems," said Yarzábal, who published a 2021 review with two colleagues exploring existing literature regarding the consequences of such a large store of microbes being steadily released back into the environment. And that's just glaciers. There are still the thawing permafrost and melting ice sheets to take into account. All of these, however unpolluted, contain their own microbial worlds. Worlds with between ten and 100 million microbes per milliliter of ice, depending on the kind of ice, Yarzábal said.
"We are talking [altogether] about an amount of microorganisms which has been estimated between 10^25 and 10^28 microorganisms enclosed, entrapped in ice prisons ... So it's a huge amount of microorganisms ... Consider that there are 10^23 stars in the universe," Yarzábal told Salon.
And, he said, while many of these captive microbes are dead, plenty of them are not.
"In this group of viable microorganisms, there are some ancient ancestral pathogens, which can also reactivate ... and they can disseminate in different ecosystems and they can, of course, infect animals, plants and other microbes," Yarzábal said. Any of these could pose a problem, whether it's because we're talking about a virus that is deadly for humans, or a bacteria that infects livestock, or a type of fungus, say, that can blight plants. Disrupting the ecological equilibrium always has the potential to cause hazards to human health directly, or to risk altering or damaging the environment we depend upon or merely appreciate for its intrinsic value.
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"This is a fact," said Yarzábal. "So we can see it as a threat, and we can anticipate this problem by studying these pathogens or these microbes, by studying the ecology of glaciers and permafrost. It's a fact, so we must be prepared for what can happen."
Already we've had a warning of what could happen: in 2016, Siberia had an extremely hot summer. The permafrost melted, exposing in the process the frozen carcasses of reindeer who had died an estimated 150 years before thanks to an epidemic of anthrax. While the animals were dead, some of the bacteria in them had remained alive, and when curious living reindeer came into contact with the remains of their frozen ancestors, they became infected with the spore-forming bacteria, Bacillus anthracis. As Yarzábal told Salon, almost 2,500 animals died and many hundreds of people (who, in this area, are in close contact with reindeer, relying on them as a source of protein for food and commerce) became infected, with at least one small human child dying as a result.
Permafrost under the layer of soil (Getty Images/Stasz D Sirotkin)While Yarzábal is at work in the Southern hemisphere, in the far North, Dr. Emilie Andersen-Ranberg, senior veterinarian at the Department for Veterinary Clinical Sciences at the University of Copenhagen, has been studying Arctic pathogens that are zoonotic, meaning they cause illnesses that can spread between animals and humans.
Not all zoonotic pathogens in the Arctic are frozen, mind you, and not all frozen pathogens in the Arctic are zoonotic. But about three quarters of all human infectious diseases are zoonotic, including the majority of novel epidemics and pandemics in recent years, and there's overlap with the issue of thawing permafrost. In a paper published in December, Andersen-Ranberg and a host of co-authors describe zoonotic viruses, bacteria and parasites of concern in the Arctic, arguing that "the Arctic represents a changing world where pollution, loss of biodiversity and habitat, and maritime activity are likely driving forward occurrence of infectious diseases", with thawing permafrost being one factor among many.
How concerned should we really be about thawing zoonotic infections? In an email interview, Andersen-Ranberg told Salon that's not exactly clear.
"There is not necessarily grounds to fear that the viruses in the frozen environment are more pathogenic."
"We simply don’t exactly know. There is, however, a clear theoretical risk since glaciers and permafrost are melting and they store millennia old microbes and some of these organisms have been found to revive and re-function after thawing," she said. "For example, a wide array of both RNA and DNA viruses have been detected in thawing permafrost and have been able to re-activate, [such as] RNA viruses that are highly similar to viruses that today infect mammals. On the other hand, we are constantly exposed to potentially pathogenic viruses from various natural sources, and there is not necessarily grounds to fear that the viruses in the frozen environment are more pathogenic."
She did note, however, that thawing permafrost could re-introduce ancient pathogenic viruses that are now extinct, or where today's strains have evolved to have such a different genetic makeup that our (or other mammals') immune systems are less able to detect and fight off the ancient strains.
Such pathogens would be unknown to our immune systems, as smallpox was to the immune systems of the Indigenous people who encountered it as a result of European colonizers who brought the virus to the Americas, Australasia and elsewhere, leading to mass deaths from succeeding waves of the disease.
It's not just the resurgence of ancient diseases, but the fact that pathogens can and will trade genetic information if they come into contact with one another, a process known as viral recombination. Bacteria are also "promiscuous," easily exchanging genetic material. This could allow them to acquire genes from frozen pathogens that confer antimicrobial resistance or greater virulence. As it's common for hosts like humans or other animals to harbor more than one infection at once, there can be plenty of opportunities for gene transfer to occur. Therefore, infectious agents released from melting ice "represents an even greater pool of genetic viral diversity to be introduced in already circulating viral populations," Andersen-Ranberg explained.
"This for example means more potential ways to avoid the immune system of the host, or an increased ability to infect a variety of hosts," Andersen-Ranberg added. "Moreover, this melt-induced introduction of potential pathogens occurs simultaneously with other great changes to disease dynamics worldwide currently occurring due to climate change and changing human activities. Put simply, it's a lot happening all at once."
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So what can or should we be doing about it?
"I don't know," Yarzábal acknowledged soberly. That is, beyond what he already recommended — we must do far more to anticipate potential disease outbreaks or reoccurrences and to understand the specific pathogens we're likely to encounter. The microbiologist is not sure what other action we might take, practically-speaking, as vast areas of ice and permafrost unleash the microorganisms they've been hanging onto all these years. Unless we reduce emissions enough to keep some of those frozen pathogens in ice.
Aerial view above the glaciers melting into the permafrost of Jostedalsbreen National Park (Getty Images/MICHAEL WORKMAN)Beyond that, this is a genie that can't be put back in its bottle, only monitored and managed as it plays its tricks. But that monitoring and containment of potential disease outbreaks will be absolutely critical to protect us. In 2019, the European Academies Science Advisory Council issued a report that noted that pathogen release of infectious disease from thawing permafrost was one among various ways climate change could affect human health in Europe. And that same year, EASAC along with the US National Academies of Sciences, Engineering, and Medicine (NASEM) and InterAcademy Partnership, a global network of science, engineering and medicine societies, brought researchers and public health officials together from North America, the European Union and Russia to assess the current state of knowledge and gaps in knowledge relating to the risks similarly posed by infectious agents in thawing Arctic permafrost and ice.
But we really need much more scientific investigation to understand the degree of threat such pathogens may pose to human, animal and ecosystem health, Yarzábal said. Meanwhile, the Arctic Council, which brings together Arctic countries and Indigenous Arctic communities to share knowledge and discuss policy affecting the region, has been weakened in recent years by political divisions, and different nations' territorial ambitions.
"To me, there is a mind-blowing gap between the knowledge and worries of scientists and the opinions and aims of decision makers, i.e. an incongruent relationship between knowledge and political realities," Andersen-Ranberg told Salon. "I find this most noteworthy, because there is such relatively little emphasis on and monitoring of zoonoses as well as emerging/reemerging disease in the Arctic — an area subjected to the greatest degree of climate change in the world which currently drastically changes disease dynamics."
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