The catastrophic effect of rabbit grazing on the grasslands of Macquarie Island (Lat. 54[degree]30[image] S., Long. 158[degree]57[image] E.) supports the theory that populations of few species are likely to be unusually susceptible to external disturbances. Following grazing since the 1880''s, there has been progressive elimination of Poa foliosa and Stilbocarba polaris. These are the only two widespread dominant and stabilizing species in the limited flora, and the remaining minor species have been ineffective in preventing widespread peat erosion.