Six species of marine turtle are found on the Great Barrier Reef. The Reef region has globally significant nesting and foraging areas for green, loggerhead, hawksbill and flatback turtles. Marine turtles provide a number of ecological services, including herbivory and seagrass dispersal by green turtles, nutrient cycling and sediment production. Turtles are highly valued by Traditional Owners, visitors to the Reef and the local community.
Years of monitoring indicates that the northern Great Barrier Reef green turtle population is in decline. Raine Island is the world’s largest green turtle rookery and monitoring indicated a 20-year failure to produce sufficient green turtle hatchlings to maintain a sustainable population.
About 90 per cent of the northern Great Barrier Reef green turtle population nest on Raine Island or nearby Moulter Cay.
Management interventions implemented in recent years as part of the Raine Island Recovery Project, (a partnership between Great Barrier Reef Foundation, BHP, the Queensland Government, the Great Barrier Reef Marine Park Authority, and the Wuthathi and Meriam Nation (Ugar, Mer, Erub) Traditional Owners), have slightly improved reproductive success.
Rising air and sand temperatures as a result of climate change are the most immediate and broad-scale threats to marine turtles because the gender of hatchlings is determined by temperatures experienced within the nest. The feminisation of green turtles originating from nesting beaches in the northern Great Barrier Reef, is predicted to lead to a significant scarcity or absence of adult males in the future.
Other impacts on green turtles indicated by current research include a decline in the size of nesting adults, increases in the non-breeding periods, a lack of expected increases of turtle numbers in dispersed feeding areas, and increased flooding of nest chambers.