Great Barrier Reef, Australia

The Great Barrier Reef, the world's largest coral reef system, stretches 2,300 kilometres along Queensland's coast, yet mass bleaching events in 2016, 2017, 2020, and 2024 have killed over 50% of coral in some areas, a severity surpassing the damage observed at Raja Ampat Reef (#2). Despite this, it remains a vital stronghold for marine life, hosting over 1,500 fish species. The Australian government has invested $1.2 billion into restoration, aiming to reduce water temperatures by 0.5°C locally, faster than the global average decline for similar ecosystems.