Quantifying site and species factors to inform the feasibility of eradication of alien plants from Southern Ocean Islands: Stellaria media on Macquarie Island

Eradication of alien plants is notoriously challenging, however eradication projects reap great biodiversity benefits, particularly on islands. To date only individual plants or small restricted populations have been successfully eradicated from the Southern Ocean Islands (SOI). The next phase in conservation for the region is tackling more widespread, abundant alien plant species. Several on-going and proposed control programs for such weeds exist in the SOI and Antarctic regions. If eradication of a widespread species is to be successful, a number of factors need to be considered. ‘Organisational’ factors such as management agency capacity, resources and the availability of effective control methods are critical to the success of an eradication. ‘Site and species’ factors such as infestation extent, number of discrete populations, dispersal processes and detectability typically show a cumulative effect on success. We assessed the site and species factors for Stellaria media, an alien species on sub-Antarctic Macquarie Island, to determine the feasibility of its eradication from the island. Organisational factors can successfully be met with adequate funding. Site and species factors which reduce the likelihood of eradication included large gross infestation areas, large plants with high reproductive output (precocity or fecundity), dense seed banks, short pre-reproductive period, extended seed longevity and vegetative reproductive capacity. We recommend a small-scale eradication trial for restricted, easily accessible populations of S. media on Macquarie Island to further evaluate the likelihood of broader eradication.