46 | New Scientist | 19 February 2022
Features
In from
the cold
As ice and frozen soil around the
world melts, potentially deadly
microbes that have lain dormant
for millennia are being released.
How worried should we be?
Michael Marshall investigates LEF
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KO/ALAMYlike wildfire. Before the outbreak was brought
under control, more than 2000 reindeer had
perished. Dozens of people also caught the
disease, including an unnamed boy who died.
This story could be a harbinger of what
is to come. As Earth’s icy regions thaw, long-
dormant microbes will inevitably emerge. The
organic matter in permafrost is teeming with
them, and even glaciers and ice sheets aren’t
the pristine environments once imagined.
How likely is it that these microbes – some of
which have been trapped for millions of years –
will defrost and come back to life? If they do,
what risk could they pose to humans? Might
we even be exposed to ancient diseases that
once infected Neanderthals and Denisovans?
These are the questions we need to answer
if we are to combat this latent threat.
About 10 per cent of Earth’s surface is
covered with ice and snow. The great ice sheetsof Antarctica and Greenland span 15.7 million
square kilometres between them. And there
are huge rafts of floating sea ice. Hundreds
of thousands of glaciers slide imperceptibly
slowly down mountainsides and valleys.
Meanwhile, the northern hemisphere alone
has 23 million square kilometres of permafrost,
soil that stays below 0°C for at least two
consecutive years, mostly in Siberia, the
Tibetan plateau and the far reaches of North
America. Climate change is melting it all.
Greenhouse gas emissions have already
warmed the planet by 1.1°C. In the Arctic,
warming is at least twice and possibly three
or four times that. Arctic sea ice is shrinking
and will probably decline to less than a million
square kilometres at least once by 2050.
Glaciers are retreating ever further up their
valleys. And the ice sheets of Antarctica and
Greenland are slowly falling apart at the edges.I
N NOVEMBER 2019, the US National
Academies of Sciences, Engineering and
Medicine held a workshop to discuss an
emerging disease threat. Not covid-19: they
were a couple of months too early for that.
Instead, they were trying to figure out what to
do about microorganisms trapped in glaciers,
ice sheets and permafrost, which will be
released as the world warms and the ice thaws.
During the meeting, Alexander Volkovitskiy
from the Russian Academy of Sciences
recounted an alarming incident. It took place
in 2016 on the Yamal peninsula on Russia’s
northern coast where local people herd
hundreds of thousands of reindeer. That
summer, temperatures were unseasonably
warm and some of the permafrost thawed.
The bacterium that causes anthrax – which
had been present on the peninsula for over a
century – emerged from the soil and spread