Scientists have found that the fringes of the Antarctic are being invaded by hitch-hikers in the form of non-native plants and even tiny animals.
A two-month survey of visitors has found that many are carrying plant seeds picked up from other countries, Reuters reports.
The scientists, writing in the Proceedings of the National Academy of Sciences Journal, say invasive alien plants are amongst the most significant conservation threat to Antarctica, especially as climate change warms the ice continent.
More than 33,000 tourists and 7000 scientists visit Antarctica each year by ship and aircraft.
The scientists vacuumed travellers' pockets, trouser and sleeve cuffs, shoes and inside their bags, and used tweezers to pry out accidentally hidden seeds.
One of the seeds found, that of annual winter grass, has established on King George Island in the past couple of seasons.