The Great Barrier Reef (GBR) is the largest contiguous coral reef ecosystem in the world81,49. That it is possibly the largest geomorphological structure ever created by living organisms is less widely appreciated. The GBR extends through approximately 15 degrees of latitude and more than 2100 km along the northeast Queensland coast, covering an area of 344,500 km282. It includes more than 2900 reefs of varying types (eg fringing, patch, cresentic, lagoonal, planar), dimensions and stage of growth, which together occupy greater than 20,000 km2, or about 5.8 percent of the total area of the GBR81,82. Three hundred or so coral cays, and more than 600 continental or high islands occur within the GBR. The mainland coast, which can be broadly separated into sandy shorelines and mangrovelined muddy coasts and estuaries (rocky coasts are far less common)80, is another important and dynamic geomorphological component of the GBR.