Field observations of the effects of succession of vegetation, grazing by the moth Fraus simulans on the sedge Ecdeiocolea monostachya in a long unburnt area, the post-fire survival and regeneration of established tussocks and the survival of seedlings germinating in the first winter following burning are presented. There was considerable post-fire mortality of the established tussocks and in only one of the three areas burnt did any of the seedlings survive successive summer droughts. Surviving seedlings did not replace the tussocks killed by the burning. The possible effects of fire, drought and insect grazing on the biotic composition of small reserves are discussed. It is suggested that the information presented provides a basis for a formal decision process for risk assessment when managing reserves for retention of biodiversity and fire hazard reduction.