The population of Agrostis trachychlaena is though to number fewer than 250 mature individuals. The species has only been found once on Inaccessible Island, and on Nightingale Island the dense cover of Spartina arundinaccea makes it difficult to accurately estimate the population size. It is thought that Agrostis trachychlaena occupies a total area of less than ten square kilometres, and, together with its small population, this makes it particularly vulnerable to extinction (1). Although thought to be naturally scarce, possibly because of natural erosion of the volcanic islands and the subsequent loss of habitat, potential man-made threats include the introduction of non-native plant species, and fire (1). In particular, introduced New Zealand flax (Phormium tenax) has the potential to exclude native plant species, and increasing tourism on the islands means an increasing potential for future introductions of alien species (3). Non-native invertebrates, including earthworms, slugs and woodlice, have also been introduced to Inaccessible Island, with unknown effects on its ecology (3).