Because of its hostile climate and remote location, Antarctica is one of the most pristine environments on Earth. But the icy continent is playing host to ever-increasing numbers of scientists and tourists, and a new study finds that these visitors are bringing some unintended baggage: the seeds of potentially invasive plants. Climate change is projected to render the frigid continent more hospitable to such plants in coming decades, says the study's lead author, Steven Chown, an environmental scientist at Stellenbosch University in South Africa.
Recently, Chown and his colleagues conducted the first continentwide assessment of the risk of invasive plants. In late 2007 and early 2008, the researchers inspected the travel gear of more than 850 scientists, tourists, support personnel, and ships' crew (with their permission). That's approximately 2% of Antarctic visitors during that period, Chown notes. Using vacuum cleaners at the visitors' first stop on the continent, they collected almost 2700 seeds from equipment including outerwear, footwear, day packs, and camera bags.
Although about 20% of tourists had unwittingly carried seeds to Antarctica, more than 40% of the scientists and support personnel at research stations had brought botanical stowaways—and more than half of the scientists doing field research and tourist support personnel, such as tour guides, harbored hitchhikers. Overall, the researchers estimate that all visitors to Antarctica that field season brought about 71,000 seeds. On average, each seed-bearing visitor carried more than nine seeds, Chown and his colleagues report online today in the Proceedings of the National Academy of Sciences.
Analyses of the types of seeds gathered, together with information from questionnaires about the visitors' travel habits in the year before their Antarctic visit, suggest that between 50% and 60% of the seeds reaching Antarctica arrived from areas with similarly cold climates—and therefore pose a threat of gaining a foothold. By 2100, climate change could dramatically boost the risk of nonnative species becoming established, especially along the western Antarctic Peninsula and in ice-free coastal areas west of the Amery Ice Shelf and along the western Ross Sea, the researchers estimate.
Previous studies had estimated the risk of invasive species for limited areas of Antarctica and were based only on the numbers of visitors or the amount of cargo shipped, Chown says.
"This is an extremely important paper," says Peter Convey, an ecologist with the British Antarctic Survey in Cambridge, U.K. "This research was an obvious next step, but a big one," he notes. "Their risk estimates are based on objective data rather than hand waving."
Philip Hulme, an ecologist at Lincoln University in New Zealand, agrees: "Now we know what's coming in and what might get established." Many factors influence whether a seed could actually take hold in Antarctica, he notes, including the nutrient content and pH of soil. Nevertheless, he adds, researchers can't presume that Antarctica is immune to invasion. "In the long term, it's going to be a big problem," he notes.
In the meantime, there are a few inexpensive and easily implemented measures that visitors can take to help stem the tide of invasive species, Chown says. Tourists can clean their equipment thoroughly, including vacuuming their gear bags and emptying the pockets of their outerwear, especially if they've recently visited arctic or alpine environments where they could have inadvertently picked up seeds of cold-adapted plants.
Also, scientists can pay attention to where cargo destined for Antarctica is stored, especially if it's been stored outdoors. Sometimes, Hulme says, researchers get the most out of their investment in cold-weather gear by using the equipment in Antarctic fieldwork half the year and then transporting it to arctic environments, where it can easily pick up stowaway seeds.