In 2012, a group of scientists conducted a study in which they vacuumed the clothes and gear of visitors to Antarctica – tourists, boat crews, researchers and others – before they disembarked from their plane or boat.
The debris was then combed for seeds and plant parts that can grow in soil, revealing that the participants unwittingly carried an average of 9.5 seeds and plant parts on their clothing and equipment. The Antarctic-bound researchers tended to be bigger offenders than the tourists, accounting for an average of twice as many seeds.
“Oh god, that was disgusting,” laughs Dana Bergstrom, an applied ecologist and principal research scientist with the Australian Antarctic Program who initiated the study. “You don’t want to know what people put in their pockets!”
The study underscores the role of humans in spreading biological entities in parallel with our own movements: microbes on our skin, seeds stuck to our clothing, bugs in our food, barnacles on the hulls of boats. Many of these micro-travellers will not survive the journey or won’t be able to thrive in the new environments in which they find themselves. But some will take off, and take over, claiming the niches of native species and changing ecosystems, often irreversibly.
For the most isolated continent and one of the most fragile ecosystems on Earth – Antarctica – this is beginning to pose major threats.
Antarctica has so far seen few such invasions, largely thanks to its extremely cold temperatures, lack of a resident human population and reachability – as well as careful oversight through the Protocol on Environmental Protection to the Antarctic Treaty, which comprehensively protects the continent as a natural reserve. So far, just 11 non-native invertebrates and one grass are known to have established themselves on Antarctic land. Scientists have also seen non-native species in the marine environment but have not yet observed their full establishment, likely because it’s too cold for them to survive and thrive.
That’s fortunate: Antarctica’s native species are particularly unique, having adapted over millennia to survive in harsh conditions, and many are yet unknown. Just last year, scientists at Australia’s Monash University found a type of bacteria that gets its energy from hydrogen and is able to make its own water.
But as the planet warms – and Antarctica gets busier with more tourism, new research stations and rebuilding projects – there’s an increasing chance that rogue species will find a foothold and outcompete their endemic counterparts. “Antarctica is sort of lucky that not much has gotten through yet,” says Bergstrom.
However, things are changing very rapidly, particularly on the Antarctic Peninsula – the northernmost corner of the continent, which draws an elongated ’S’ shape toward South America’s Tierra del Fuego. Sea temperatures now sit above zero degrees centigrade for about three months of the year, heightening the chances of a non-native species completing a lifecycle and establishing itself.
“As climate change combines with non-native species, these biological barriers are starting to fray at the edges,” says Bergstrom. “We can see it, so can we prepare ourselves to stop it? If those barriers are no longer working, what else can we do?”
Mapping and mitigating incursion risks
One element of protection is assessing likely origins of non-native species. In a just-published study, researchers at the University of Cambridge mapped ship traffic to Antarctica from 2014 until 2018, which included tourism, fishing, research and supply vessels. They found that shipping connected the continent directly to all global regions, meaning that non-native marine species could potentially arrive from any part of the world.
As most ships only travel to Antarctica in the summer season, they therefore spend considerable time elsewhere for the rest of the year, picking up organisms like barnacles, mussels and seaweeds on their hulls as they do so. Knowing where these vessels go can help with monitoring and risk assessment, says Arlie McCarthy, the study’s lead author and a doctoral candidate at the British Antarctic Survey. “If a ship has spent the last three years in the tropics, and then takes one voyage to Antarctica, its biofouling is probably going to be mostly tropical species, which are not likely to survive the trip,” she says. “But if it’s a vessel that spends most of its time in cold water, such as in the Arctic or southern South America, then that presents more of a risk.”
Bergstrom calls for collective action from Antarctic Treaty member states to ensure that all ships that go to Antarctica are biologically safe. One way to do so, she says, is to funnel ships through the five major ‘gateway’ cities to Antarctica – Christchurch, New Zealand; Hobart, Australia; Cape Town, South Africa; Punto Arenas, Chile; and Ushuaia, Argentina – where they can be cleaned, rather than relying on sea ice to scrape their hulls. “There have been quantum leaps in ship hull cleaning technologies, and ship design is improving, though we’ve still got a lot of old ships,” she says.
On land, her suggestions are similar: design studies that identify the pathways by which species are entering and create barriers against them doing so. Since the vacuuming study mentioned at the start of this article was conducted, several countries with Antarctic research programs, such as Australia and New Zealand, have set up mitigation processes, such as by issuing designated Antarctic clothing and gear that is not worn or used anywhere else.
Once these kinds of barriers are set up, surveillance and early intervention mechanisms are critical for ensuring the species that slip through the cracks can’t get established. Winter grass, Poa annua, an invasive European weed that is the bane of golf courses across the globe, has become established on a number of sub-Antarctic islands and made it to the Antarctic Peninsula multiple times. “And every time, the national programs are hammering it,” says Bergstrom. “You can’t do that unless you have long-term monitoring programs backed by rapid action.”
To Antarctica: Invasion or evolution?
All ecosystems change over time, and some fresh arrivals will make their way to the continent without human help. “We don’t want to stop the evolutionary process,” says Bergstrom. “But if you’re not sure whether it looks like a natural arrival, my argument is to take it out, because if it is [natural], it will get there again. It’s best to err on that side and have no regrets.”
Microbes are another matter: we all bring multitudes of them with us, and they’re pretty difficult to eradicate. Even COVID-19 made it to Antarctica last year. ‘Reverse zoonosis,’ where humans transmit disease to animals, is a considerable concern: penguin and seal populations might be particularly vulnerable to human-borne diseases.
“Right now, there’s this heightened focus: we have this one moment in time to really protect Antarctica, and if we don’t get it right, it will just follow the rest of the planet into homogenization,” says Bergstrom.