The Great Barrier Reef stretches approximately 2,300 kilometers along the northeastern coast of Australia, off the state of Queensland. It is made up of roughly 2,900 individual reefs and around 900 islands, covering an area of about 344,400 square kilometers, making it the largest coral reef system on the planet and the only living structure visible from space.
The reef is built by tiny animals called coral polyps, which secrete calcium carbonate to form hard skeletons. Over thousands of years, generations of polyps build upon the skeletons of their predecessors, gradually forming the massive limestone structures that make up the reef. Most reef building coral relies on a symbiotic relationship with microscopic algae called zooxanthellae, which live inside coral tissue and provide the coral with food through photosynthesis in exchange for shelter.
The reef supports an extraordinary range of life, including around 1,500 species of fish, 400 species of coral, 4,000 species of mollusk, and 240 species of birds. It is also home to endangered species such as the dugong and the large green turtle, and provides breeding grounds for humpback whales that migrate through the region each year.
UNESCO designated the Great Barrier Reef a World Heritage Site in 1981, citing its outstanding natural beauty and ecological significance. The Great Barrier Reef Marine Park, established in 1975 under Australian federal law, governs much of the reef's protection and manages the balance between conservation, tourism, and fishing activity.
Rising ocean temperatures have caused repeated mass coral bleaching events, when stressed coral expels its symbiotic algae and turns white, often leading to death if warm conditions persist. Significant bleaching events occurred in 1998, 2002, 2016, 2017, 2020, and 2022, with the 2016 and 2017 events combined affecting more than two thirds of the reef's coral. Scientists generally attribute this pattern to warming sea temperatures linked to climate change.
The reef contributes significantly to the Australian economy, primarily through tourism. Estimates commonly cited by Australian government bodies place its economic value, including tourism, recreation, and fishing, in the tens of billions of Australian dollars annually, supporting tens of thousands of jobs in the Queensland region.
Various programs work to protect the reef, including coral restoration projects that grow coral fragments in nurseries before transplanting them onto damaged sections of reef. The Australian government's Reef 2050 Plan outlines long term strategies covering water quality, crown of thorns starfish control, an invasive predator that consumes coral tissue, and climate resilience measures.