Rapid survey for Pisonia grandis - Bajigal and Bimi (Stephens and Sisters islands) Supplementary island threat assessment report

Abstract

This report presents the findings of rapid ecological assessments undertaken on Bajigal (Stephens Island) and Bimi (Sisters Island), located on Mandubarra Country in north Queensland. The study focuses on identifying and assessing populations of Pisonia grandis and associated ecological values and threats across the two islands. Using a rapid survey approach, the assessment provides a snapshot of island condition, including the presence of key threatening processes such as invasive species, cyclone impacts, and the occurrence of soft scale (Pulvinaria urbicola), a known driver of decline in Pisonia forests elsewhere in the Great Barrier Reef. The surveys also document broader biodiversity values, including seabird nesting habitat, littoral rainforest communities, and regionally significant flora. The findings are intended to complement existing management knowledge and support targeted conservation actions by outlining current ecological conditions and potential risks to Pisonia-dominated systems. This report provides a practical evidence base to inform management and monitoring efforts aimed at maintaining and enhancing island ecosystem health within the Great Barrier Reef World Heritage Area. This work forms a key deliverable under the Restoration of Reef Islands Project, delivered through the Reef Joint Field Management Program (Great Barrier Reef Marine Park Authority and Queensland Parks and Wildlife Service) in partnership with Mandubarra Land and Sea Inc, and Aestra as the environmental delivery partner, and funded by the Australian Government’s Reef Trust. The project aims to support the rehabilitation, enhancement, and long-term resilience of island ecosystems within the Great Barrier Reef World Heritage Area.