AS TOURISTS wait for their bags at Sydney airport, a beagle scampers about their feet. If the pooch detects a foreign organism, such as plant matter or meat products, the Australian quarantine authorities confiscate and incinerate it. This is done to protect Australian species from a potentially calamitous alien invasion.
In Antarctica, one of the most uncorrupted ecosystems in the world, there are no beagles. But as the number of tourists and scientists visiting the icy continent increases, so do the numbers of alien seeds and other organisms inadvertently tagged to their shoes or clothes. With climate change rendering Antarctica increasingly hospitable to species from temperate climes, it faces just the sort of invasion feared by Australia.
According to a study published in Proceedings of the National Academy of Sciences (PNAS), each visitor to Antarctica unwittingly brings on average 9.5 alien seeds. Steven Chown of South Africa's Stellenbosch University and colleagues checked the clothes, boots, walking poles and bags of a sample of visitors to Antarctica in 2007-08. They found that scientists tend to arrive with many more seeds on their person than do tourists. But as there were many more tourists than scientists, their impact was similar. They estimate that tourists brought in just under 32,000 seeds that year. Scientists carried almost 39,000 seeds.
Over half of the alien seeds came from places with species that are known to be capable of surviving in Antarctica. This makes them potential invaders of the continent's relatively warm coastal regions. Already, Poa annua, a species of European grass, has spread from the Polish research station on King George Island, the largest of the South Shetland islands.
The Antarctic ecosystem is valued by scientists as a place largely free of human influence. But this is increasingly not the case. To protect its indigenous species, the study in PNAS recommends stringent checking of visitors, and establishing other detection systems, such as satellite-tracking of seabirds and monitoring wind trajectories, to pick up non-human forms of transport.