We Worried About Zombie Viruses Under the Permafrost. There’s Something Much Scarier Frozen Beneath It

This story is part of Dark Horizons, our new series about science and technology’s dimmest corners and outermost limits. Here is a second, third and fourth piece — as well as more about the package.

IN THE summer of 2016, a terrifying disease clawed its way out of the previously frozen ground: anthrax. Melting permafrost in the far reaches of Siberia awakened bacterial spores that had been dormant for almost a century, infecting thousands of reindeer in the region and eventually sickening dozens of people and killing a 12-year-old child. 

More recently, scientists have intentionally managed similar, if less risky feats, reanimating dormant microbes that in some cases have spent tens of thousands of years frozen in place. In response, the media, both traditional and social, has blared the headlines from the rooftops: The “zombie” viruses are coming.

The permafrost, after all, is in trouble as the climate warms. The northern reaches of the planet are warming as much as four times faster than the global average. But even as the headlines grabbed hold of the zombies, the melting permafrost is actually hiding something far scarier: carbon. 

There is an enormous amount of methane and other carbon sources trapped in the frozen ground, and if it makes its way into the atmosphere it could have a profound effect, one of climate change’s nastier feedback loops — warming begets melting begets more warming. From a global perspective, with the urgency to address the changing climate now at a fever pitch, the zombies can’t really compete.

“I think the virus story is a distraction,” said Christopher Burn, a professor at Carleton University in Canada. “There have been people living with permafrost now for 5,000 years and more… and we don’t characteristically have problems associated with strange diseases coming out of permafrost. That’s not our common experience…. In my view, the viruses are an anecdote.”

PERMAFROST IS defined as any ground that has maintained a temperature below freezing for at least two years. In total it covers some 8 million square miles — an area bigger than the entire United States — primarily in Russia, Canada and Alaska. Some of it, if one digs deep enough, has been frozen for hundreds of thousands of years. Overall, it contains an astonishing amount of carbon.

In just the top ten feet or so of frozen ground, there is around one trillion tons of carbon. That’s double the total amount that’s currently in the atmosphere — if warming causes the release of only 1% of it, that’s equivalent to about a year’s worth of human-caused emissions. 

For years scientists believed the Arctic was a carbon sink, storing more carbon in vegetation than it released. But research published in 2019 suggested that equation had flipped, with far more carbon released than was taken up by plants. Since then the scientific community has argued some over the precise parameters, but as temperature records continue to fall it is clear that the carbon stored in permafrost is increasingly an issue.

Importantly, though permafrost has been called a carbon “bomb,” it is more likely a slow-burn of a problem than some single catastrophic event, releasing more and more into the atmosphere year by year.

Another issue, experts say, is more local, and more immediate: if the ground beneath your feet is melting and softening, anything you build on it isn’t going to last.

One way that manifests: landslides. “If you analyze the number of landslides in the Arctic… over the past 10 years, you will be amazed,” said Ekaterina Uryupova, a senior fellow at the Arctic Institute.. The shifting ground has already resulted in collapsing roads, damaged buildings, and more, causing huge problems in particular for indigenous people who have made their homes in the far north for thousands of years.

Military installations, pipelines, even drinking water supplies are being impacted by the ongoing melt. As coastlines erode and change, entire towns, like Newtok, Alaska, are being forced to relocate. Infrastructure like offshore oil rigs could even be at risk, though much less is known about the potential for melting of the undersea permafrost on which those rigs are sometimes anchored.

To contend with the melting permafrost, building costs in the Arctic have risen in many areas. For example, some buildings require chilled foundations, raising both capital and maintenance costs.

One short section of the Alaska Highway recently required permafrost-related updates, and it cost $4 million for less than one-third of a mile. The whole highway stretches more than 1,300 miles, meaning wholesale fixes are essentially out of the question. “You’d be into the billions of dollars, and people aren’t going to support that,” Burn said. “People know that climate change is coming — or, not coming, it’s here.”

THAT’S NOT to say the zombies aren’t out there — but they might attract more attention than they deserve. In late 2022, a group of researchers led by Jean-Michel Claverie of Aix Marseille University published a study reporting on the successful revival of 13 viruses taken from Siberian permafrost. They focused on viruses that infect amoeba and pose no danger to people, but Claverie has warned that this research does indicate some “danger coming from the north” as the climate warms.

An analysis in that paper’s wake by researchers in India found that mentions of zombie viruses online reached more than 300 million social media users over the month following the paper’s release, and while plenty of the chatter could be chalked up to memes and jokes there was also misinformation spreading beyond the paper’s actual findings.

“Print, television, and social media currently act as double-edged swords,” the authors of that analysis wrote. “Despite their best efforts to educate and entertain the audience, due to a lack of appropriate training, they are sometimes forced to gloss over health-related issues that require a more nuanced understanding and mature perspective.”

Speaking just after returning from more than three months of field research in the Arctic, Uryapova said it makes perfect sense that some microbes could survive the long dormancy inside permafrost, but their spread doesn’t keep her up at night either. “Usually we can isolate things very fast,” she said, meaning any suddenly reanimated microbe probably won’t spread beyond the local area.

Bo Elberling, a professor at the University of Copenhagen and director of the Center for Permafrost, has led research aimed at determining if the microbes could travel after thawing out. His team studied “kitchen middens,” remains of living spaces of indigenous people in West Greenland dating back 3,000 years, and though they did find DNA of viruses in the permafrost there was no indication that they spread beyond the site itself. “We have no evidence that viruses from the middens can be alive or [pose] any risk to human health,” Elberling said.

They also collected 1,000-year-old permafrost samples near Greenland’s capital, Nuuk, to test if sheep viruses from old farming sites could pose a problem if sheep return to the area. They found nothing concerning, he said. 

“In all our work we find DNA of viruses in permafrost samples, we know that viruses easily can survive repeated freezing [and] thawing,” Elberling said. “But we have not found any viruses from permafrost layers we consider a risk for human health.”

Uryupova said that bacteria are much more likely to survive and pose some localized risk — like in the case of the anthrax outbreak in 2016 — than zombie viruses are to wake up and cause some sort of massive plague. “I think we are very much prepared for all kinds of unexpected things,” she said. “In terms of finding something else that can, you know, kill all of humanity? I don’t think so.”