Assessing the medium-term risk to reef damage and rubble generation for the Great Barrier Reef

Coral reef systems live in multi-hazard environments and are exposed to a wide range of disturbance events that operate at different spatial and temporal scales. We identify seven drivers derived from hazards that have and can result in reef damage in the Great Barrier Reef (GBR): waves, winds, bottom current velocity, coral bleaching, crown-of-thorns seastar outbreaks, ship groundings, and tsunamis. We map these drivers individually, apply damage thresholds where applicable, and combine the normalized drivers into an additive vulnerability index for the GBR. The Index can be applied at a range of scales from reef groups to the entire reef system and we show that the GBR has a moderate risk profile to damage. Risk to reef damage broadly increases towards the central region with lowest risk at the northern and southern ends of the GBR. Specific hotspots of high risk to damage are identified including the Cairns region and Swains Reef area. The Cape York and Mary Burnett Natural Resource Management zones represent regions with the lowest vulnerability scores and, therefore, are important to consider as potential refugia and nurseries for restocking reefs damaged in other parts of the GBR. Our approach takes a comprehensive and holistic view of all the disturbance drivers that the GBR experiences and will continue to experience in the coming decades at different frequencies and intensities. Given that substantial effort and resources are now being directed globally to active restoration of coral reefs, such efforts can be undone if management activities do not take a holistic approach to disturbance drivers.