Marine Reserves Ranked by Size, From 20 Hectares in Hong Kong to the Waters Around Niue

Begin with the smallest: about 20 hectares at the south-east corner of Hong Kong Island, designated in July 1996 under the Marine Parks Ordinance to protect rocky shore and subtidal habitats. It is Hong Kong's only marine reserve as distinct from its marine parks, and the Swire Institute of Marine Science of the University of Hong Kong supports it on site.

Piti Bay on the west coast of Guam covers about 3.64 square kilometers and was established in 1999 as one of five marine protected areas on the island. Its name comes from freshwater percolation pits in the reef flat that look like bomb craters, and its underwater observatory draws more than 200,000 visitors a year.

About 33 square kilometers of reef, lagoon and small islets on the western side of Funafuti atoll in Tuvalu, established in 1999. It protects roughly a fifth of the lagoon's coral reef, its islets host nesting green sea turtles, and the islet of Fualopa has a breeding colony of black noddy.

At the northern end of Ambergris Caye in Belize, this reserve covers about 107 square kilometers of swamp, grassland, forest and sea, including part of the Mesoamerican Barrier Reef System. It is listed under IUCN Category IV despite the words National Park in its name, and it was created after surveys found unusually high biodiversity for a barrier island.

An uninhabited atoll of low sandy islands in the Gulf of Honduras, administered by Belize but also claimed by Guatemala and Honduras. The marine reserve over it, set up in 1996, spans 15,618 hectares (about 127 square kilometers), is IUCN Category IV and protects bird populations that include red footed boobies.

Also called the Cargados Carajos Shoals, this Mauritian archipelago in the southwest Indian Ocean has only about 1.3 square kilometers of land but a reef area of about 190 square kilometers. A management plan was approved by the Mauritian government in 2004, and the protected area sits alongside a working fishery run from a base of around 40 residents.

Established in 1996 in Myanmar's Mergui Archipelago, this park covers about 204.8 square kilometers around Lanbi Island and smaller islands. It joins coral reefs, seagrass beds, mangroves and dunes to evergreen forest rising to about 455 meters, and it is an Important Bird Area and an ASEAN Heritage Park.

End with the largest: 318,140 square kilometers, covering the territorial waters and exclusive economic zone around the Pacific island of Niue. Established in April 2022, it absorbed two earlier areas created in 2020 and is split into five zones, the strictest protecting Beveridge Reef.