The conservation status of the Black Grassdart ButterflyOcybadistes knightorum:a species at risk from climate change

Abstract

The Black Grass-dart Butterfly 'Ocybodistes knightorum' has a highly restricted distribution along the New South Wales north coast and is listed as an Endangered species in the State. Recent surveys have dramatically increased the known distribution of the species, warranting a reassessment of its conservation Status. Fine-scale mapping of the entire known habitat of the species enabled a detailed assessment to be conducted that was commensurate with the small size of the butterfly and the fine-grained environmental data available. We evaluate the Status of 'O. knightorum' against IUCN Criteria B (Geographic Range). The butterfly was found to have an extent of occurrence of 312 km2 and an area of occupancy of 76 km2, at three locatlons. A detailed digital elevation model was used to demonstrate the likelihood of continued decline due largely to sea-level rise induced by climate change. An estimated 85% of the current habitat of 'O. knightorum' will become unsuitably saline by 2100 according to the best currently available sea-level rise prediction. Weed invasion and anthropogenic disturbance are also serious threats, contributing to continued decline in some areas. Adopting a precautionary approach, we assess the species as Endangered under IUCN criteria.