Great Barrier Reef
The Great Barrier Reef is the world's largest coral reef ecosystem, stretching about 2,300 kilometres along the Queensland coast of north-eastern Australia. Composed of roughly 3,000 individual reefs and more than a thousand islands and cays, it was inscribed as a UNESCO World Heritage Area in 1981 and supports an extraordinary concentration of marine life, from 450 hard-coral species to dugongs and six of the world's seven marine turtles. Since 1998 the Reef has suffered eight mass coral bleaching events driven by warming seas, and its long-term outlook is rated 'very poor' — even as a 2026 UNESCO decision kept it off the List of World Heritage in Danger.