MELBOURNE, Australia — The United Nations issued a dire alert on Monday, warning that many of the world’s coral reefs could die as soon as 2040 as a result of climate change.

Already, warming waters have bleached more than two-thirds of the coral in the Great Barrier Reef, the world’s largest coral reef ecosystem, which covers more than 130,000 square miles and is visible from space.

But the Great Barrier Reef, despite its status, is not the only unique or threatened marine ecosystem in Australia.