Most southerly coral reef

The world's southernmost coral reef ecosystem is found off the western flank of Lord Howe Island – a dependency of the Australian state of New South Wales – located in the Tasman Sea at a latitude of 31.53° S. It lies within the 460-square-kilometre (180-square-mile) Lord Howe Island Marine Park, which was established in 1999.

Lord Howe Island and the nearby 561-m (1,840-ft) Ball's Pyramid (the world's tallest sea stack) are ancient seamounts that formed part of a once-extensive volcanic system active in the Late Miocene (11.6–5.3 million years ago).

A combination of tropical and cool waters, and varied habitats such as a barrier reef and vast lagoon, make the seas around Lord Howe Island a haven for wildlife including some 500 fish species, 90 coral species and at least 235 species of algae. The island and its surrounding waters were made a UNESCO World Heritage Site in 1982.

In 2019, scientists reported the most severe coral bleaching ever documented at Lord Howe Island's reefs, with some sites close to the shore exhibiting as much as 80–90% bleaching. Coral bleaching is when coral expels its symbiotic algae, caused by external stressors such as pollution or overly warm water, leaving behind a white skeletal structure that in most cases is irrecoverably damaged.