 It was initially recorded in 1987 in two deglaciated areas of Heard Island not previously exposed to human visitors, while being absent from known sites of past human habitation.Since 1987 "Poa annua" populations have increased in density and abundance within the original areas and have expanded beyond them.Expeditioner boot traffic during the Australian Antarctic program expedition in 1987 may be at least partly responsible for the spread, but it is probably mainly due to dispersal by wind and the movement of seabirds and seals around the island.