Coral Sea Islands

The Coral Sea Islands Territory is an external territory of Australia comprising a widely scattered collection of small, low-lying tropical islands, reefs, and atolls located in the Coral Sea to the northeast of Queensland. Almost the entire territory consists of open ocean, with land areas restricted to a series of tiny cays and islets. The only inhabited location is Willis Island, which hosts a meteorological station. The territory’s outer boundary lies just beyond the edge of the Great Barrier Reef, which itself forms the maritime border between Queensland and the Coral Sea Islands.

Historical Background and Legal Status

The islands were first charted in 1803 during the early period of European exploration in the region. In the late nineteenth century, several of the islands were exploited for guano extraction, a common practice in the Pacific during that era. However, the absence of fresh water resources prevented permanent settlement and limited the scale of these activities.
The Coral Sea Islands became an official Australian external territory in 1969 through the Coral Sea Islands Act. In 1997, the territory was expanded to include Elizabeth Reef and Middleton Reef, located nearly 800 kilometres south of most of the other island groups and closer to Lord Howe Island than to the main cluster around Cato Island.
The islands associated with the Great Barrier Reef are not part of this territory; they belong to Queensland. The Coral Sea Islands Territory is administered from Canberra and has been managed historically by several federal departments. It is notable as the only external Australian territory not acquired through British transfer or United Nations mandate.
Australia retains full defence responsibility for the area. The Royal Australian Navy regularly patrols the region, and the Commonwealth operates numerous automatic weather stations across the reefs. The territory has no permanent population beyond the small team on Willis Island and hosts no substantial industry other than a modest charter fishing and diving sector. In 2011, the Australian government announced plans to establish a large protected marine area in the Coral Sea.
Judicially, the Supreme Court of Norfolk Island has jurisdiction over the territory, while the laws of the Australian Capital Territory apply. The territory’s international codes include the FIPS 10-4 identifier CR, and it is covered under Australia’s ISO 3166 designation.
In 2004, a symbolic protest movement proclaimed the “Gay and Lesbian Kingdom of the Coral Sea Islands”, centred largely on political advocacy. This informal entity was dissolved in 2017 following the national marriage equality survey.

Physical Geography and Environmental Features

The territory consists of roughly 30 separate reefs and atolls, of which twelve are wholly submerged or only emerge at low tide. Approximately 51 islets and cays occur across the territory, with clusters concentrated in major reef complexes such as Willis Islets, Lihou Reef, and the Coringa–Herald group. Many cays are vegetated but all are extremely low, generally only a few metres above sea level.
The Coral Sea is characterised by deep waters between the reefs and atolls. Atoll sizes vary dramatically, from relatively small structures a few kilometres across to Lihou Reef, one of the world’s largest atolls by total area, encompassing a lagoon of substantial extent but possessing a combined land area of less than one square kilometre distributed across eighteen tiny islets.
The islands serve as important nesting sites for seabirds and marine turtles, although natural resources are minimal. There are no harbours or ports, and vessels rely on offshore anchorage.

Northwestern Reef Groups

A large number of the territory’s reefs lie on the Coral Sea Plateau (also known as the Queensland Plateau), an extensive submarine platform at depths of less than 1,000 metres.
Key features include:

• Osprey Reef, a substantial submerged atoll with a deep lagoon.
• Shark Reef, an elongated submerged feature south of Osprey Reef.
• Bougainville Reef, a small submerged atoll that dries at low tide.
• East and West Holmes Reefs, neighbouring submerged atolls with small cays.
• Flora Reef, Diane Bank, and the North and South Moore Reefs, each possessing varying lagoonal structures.
• Willis Island Group, a sunken atoll with three principal islets: North Cay, Mid Islet, and Willis Island itself.
• Magdelaine Cays and Coringa Islets, which form part of a partially sunken atoll nearly 90 by 30 kilometres in size.
• Herald Cays, comprising North-East and South-West Cays.

Two major nature reserves established in 1982 protect many of these environments:

• Coringa–Herald National Nature Reserve, covering 8,856 km².
• Lihou Reef National Nature Reserve, covering 8,440 km².

Together, these reserves form the Coral Sea Reserves Ramsar Site, designated for the conservation of important marine and avian habitats.

Lihou Reef and Surrounding Features

Lihou Reef is the largest atoll in the Coral Sea, with a total area of roughly 2,500 square kilometres and a tiny landmass composed of several small cays. Its extensive lagoon and biological significance make it a central environmental feature of the territory.
Nearby, the Diamond Islets and Tregosse Reefs form another large partially submerged atoll complex, followed by Flinders Reefs, Herald’s Surprise, Dart Reef, Malay Reef, and Abington Reef, each contributing to the intricate reef system of the wider region.
Marion Reef, situated to the south of the Northwestern Group, is a large circular atoll complex straddling the Marion Plateau and includes three small sand cays.

Mellish Reef

Mellish Reef lies about 300 kilometres east of the Northwestern Group, making it the most geographically isolated feature of the territory. It is shaped like a boomerang and encloses a narrow lagoon. At high tide, only one permanent landform remains above water: Herald’s Beacon Islet, a small cay of approximately 57,000 square metres. This reef was first recorded in 1812 and became the site of early navigational beacons.

Southeasterly Groups

To the south, the territory includes Frederick Reefs, forming an enclosed lagoon known as Anchorage Sound. The only permanently dry land in this group is Observatory Cay, though other cays can be exposed at low tide.
Further south lie Middleton Reef and Elizabeth Reef, which were incorporated into the territory in 1997. These reefs lie significantly closer to Lord Howe Island, forming a distinct southern cluster separate from the main concentration of northern reefs.