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Ancient pathogens released from melting ice could wreak havoc on the world

28 07 2023

Science fiction is rife with fanciful tales of deadly organisms emerging from the ice and wreaking havoc on unsuspecting human victims.

From shape-shifting aliens in Antarctica, to super-parasites emerging from a thawing woolly mammoth in Siberia, to exposed permafrost in Greenland causing a viral pandemic – the concept is marvellous plot fodder.

But just how far-fetched is it? Could pathogens that were once common on Earth – but frozen for millennia in glaciers, ice caps and permafrost – emerge from the melting ice to lay waste to modern ecosystems? The potential is, in fact, quite real.

Dangers lying in wait

In 2003, bacteria were revived from samples taken from the bottom of an ice core drilled into an ice cap on the Qinghai-Tibetan plateau. The ice at that depth was more than 750,000 years old.

In 2014, a giant “zombie” Pithovirus sibericum virus was revived from 30,000-year-old Siberian permafrost.

And in 2016, an outbreak of anthrax (a disease caused by the bacterium Bacillus anthracis) in western Siberia was attributed to the rapid thawing of B. anthracis spores in permafrost. It killed thousands of reindeer and affected dozens of people.

*Bacillus anthracis* is a soil bacterium that causes anthrax.
William A. Clark/USCDCP

More recently, scientists found remarkable genetic compatibility between viruses isolated from lake sediments in the high Arctic and potential living hosts.

Earth’s climate is warming at a spectacular rate, and up to four times faster in colder regions such as the Arctic. Estimates suggest we can expect four sextillion (4,000,000,000,000,000,000,000) microorganisms to be released from ice melt each year. This is about the same as the estimated number of stars in the universe.

However, despite the unfathomably large number of microorganisms being released from melting ice (including pathogens that can potentially infect modern species), no one has been able to estimate the risk this poses to modern ecosystems.

In a new study published today in the journal PLOS Computational Biology, we calculated the ecological risks posed by the release of unpredictable ancient viruses.

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Tags: bacteria, biodiversity, diversity, extinction, Global warming, meltwater, microorganisms, pathogens, time-travelling pathogens, viruses
Categories : birds, climate change, conservation, conservation biology, disease, zombie

Classics: The Living Dead

30 08 2008

‘Classics’ is a category of posts highlighting research that has made a real difference to biodiversity conservation. All posts in this category will be permanently displayed on the Classics page of ConservationBytes.com

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Tilman, D., May, R.M., Lehman, C.L., Nowak, M.A. (1994) Habitat destruction and the extinction debt. Nature 371, 65-66

In my opinion, this is truly a conservation classic because it shatters optimistic notions that extinction is something only rarely the consequence of human activities (see relevant post here). The concept of ‘extinction debt‘ is pretty simple – as habitats become increasingly fragmented, long-lived species that are reproductively isolated from conspecifics may take generations to die off (e.g., large trees in forest fragments). This gives rise to a higher number of species than would be otherwise expected for the size of the fragment, and the false impression that many species can persist in habitat patches that are too small to sustain minimum viable populations.

These ‘living dead‘ or ‘zombie‘ species are therefore committed to extinction regardless of whether habitat loss is arrested or reversed. Only by assisted dispersal and/or reproduction can such species survive (an extremely rare event).

Why has this been important? Well, neglecting the extinction debt is one reason why some people have over-estimated the value of fragmented and secondary forests in guarding species against extinction (see relevant example here for the tropics and Brook et al. 2006). It basically means that biological communities are much less resilient to fragmentation than would otherwise be expected given data on species presence collected shortly after the main habitat degradation or destruction event. To appreciate fully the extent of expected extinctions may take generations (e.g., hundreds of years) to come to light, giving us yet another tool in the quest to minimise habitat loss and fragmentation.

CJA Bradshaw