Atolls Face Rising Climate Risk as 494 Oceanic Systems Span Tropical Seas

1 articles · Updated · BBC Discover Wildlife · Aug 16

494 oceanic atolls and 104 continental atoll systems were counted in a 2023 census, with 344 in the Pacific, making the ring-shaped coral islands a widespread tropical landform.
1 to 30 million years is the timescale for atoll formation under Darwin’s subsidence model, in which coral reefs keep growing as volcanic islands erode and sink; a rival karst model instead starts with dissolved limestone islands.
About 1 million people live on coral atolls worldwide, many in the Maldives, Kiribati, the Marshall Islands and Tuvalu, tying the landform directly to human exposure.
1-2 metres above sea level is the typical elevation of most atoll land, leaving them vulnerable to sea-level rise, storm surge, saltwater intrusion and erosion as coral growth is stressed by warming, acidification and bleaching.
31 million seabirds nest on atolls—about a quarter of the world’s tropical seabirds—showing why climate pressure on these islands carries broad ecological as well as human consequences.