Dr. Costin is an international authority on the ecology of high mountain and high latitude ecosystems. His studies have provided a comprehensive understanding of the evolution of the Australasian high altitude biota and of the contemporary distribution and successional patterns of the major plant and animal communities. As part of this work he has made a unique contribution in historical biogeography, where he has developed an absolute chronology of late Quaternary events in south-eastern Australia. He has also made major contributions to the flora of the Snowy Mountains area. These investigations, together with his research in hydrology, geomorphology and conservation have had a substantial influence on public awareness and government policies concerning many aspects of conservation and environmental management.