In the frozen continent of Antarctica scientists fear an alien invasion -- not from outer space, but carried in people's pockets and bags. Seeds and plants accidentally brought to Antarctica by tourists and scientists may introduce alien plant species which could threaten the survival of native plants in the finely balanced ecosystem. "The people that were carrying the most had lots and lots of seeds. They really were real threats," said Dana Bergstrom, from the Australian Antarctic Division. "When we take things in through hitchhiking  then we get species which are competitive. The plants and animals there are not necessarily competitive, so we'd start losing various precious biodiversity  on the (Antarctic) continent", Bergstrom told Reuters. Amongst the alien species discovered were the Iceland Poppy, and Annual Winter Grass -- all from cold climates and capable of growing in Antarctica. The Antarctic Peninsula, where most tourists travel, is now considered a "hot spot" on the frozen continent and the warmer the climate, the easier for seeds to grow. "The peninsula  is warming at some of the greatest rates on the planet," said Bergstrom. The study, the first continent-wide assessment of invasive species in Antarctica, surveyed about 1,000 passengers during 2007-2008, the first year of the International Polar Year, an international effort to research the polar areas. Bergstrom said the one alien seed that had gained a foothold is Annual Winter Grass. It is a strong weed in the sub-Antarctic and is on the Antarctic island of King George. It has also made its way to the tail part of the Antarctic continent. What is the purpose of writing the passage?
To introduce the native environment of Antarctica. To warn people of the danger of alien plant seeds to Antarctica. To explain the relationship between plants and climate. To give visitors some tips on how to explore Antarctica.