English: When viewed from space, the Great Barrier Reef appears almost like a glittering, jewel-filled necklace floating off the Queensland coast. In fact, it is more precious than any jewelry.

The Great Barrier Reef is made up of a vast maze of coral reefs, passages, and coral cays, and it extends about 2,000 kilometers (1,200 miles) along the northeastern coast of Australia. It holds the Earth’s largest collection of coral reefs, providing home for about 400 types of coral, 1,500 species of fish, and 4,000 types of mollusks. According to UNESCO World Heritage Convention, the Great Barrier Reef also holds great scientific interest as the habitat of species such as the dugong (‘sea cow’) and the large green turtle, which are threatened with extinction. Nearly the entire Reef was inscribed as a World Heritage Site in 1981.

On August 19, 2023, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired a true-color image of the Great Barrier Reef and northeastern Australia.

This natural wonder is facing multiple threats, including ocean acidification and warming sea surface temperatures that cause coral bleaching as well as predation of coral by the crown-of-thorns starfish. There have been six widespread bleaching events on the reef since 1998, four of which occurred since 2016, including one in 2022.

While the 2022 event was not as severe as the previous ones, it slowed recovery of hard corals, which had been beginning to make a comeback. While recovery continues along most of the reef, scientists are finding that it is driven mostly by Acropora corals—fast-growing corals that are easily damaged by severe weather events.