Foreign seeds are hitching rides on scientists and tourists to the Antarctic and could someday upset the ecology of the warmest patches of the remote land, international researchers said.
Invasive species are "thought to be among the most significant conservation threats to Antarctica, especially as climate change proceeds in the region," said the study in the Proceedings of the National Academy of Sciences.
The research is the first attempt to quantify the threat of invasive plants and their potential effect on Antarctica.
People tend to unwittingly carry 9.5 seeds on average into Antarctica, with the some 7,000 scientists working in the region likely to have more seeds, or propagules, on them than the 33,000 tourists who visit annually.
Marc LeBouvier, a French researcher on the team, told AFP that the areas at risk include just one to two percent of the land mass which is not covered by ice.
"Invasive species are a global problem but the issue is particularly sensitive on islands where ecosystems are more fragile," he said.
"The risk in the Antarctic is an upset to the balance of the ecosystem which may result in the gradual replacement of native species with imported ones, which have the capacity to eliminate local plants."
The risks are greatest along the Antarctic Peninsula, in the coastal ice-free areas near the Ross Sea and in parts of East Antarctica, the study said.