Phoenix Islands Protected Area

The Phoenix Islands Protected Area (PIPA) sits within the Republic of Kiribati, a Pacific island nation roughly halfway between Australia and Hawaii. Spanning 408,250 square kilometers (157,630 square miles), it covers 11.34% of Kiribati’s exclusive economic zone and ranks among the largest marine protected areas—and indeed the largest protected areas of any kind—on the planet. In 2010, it became the world’s largest and deepest UNESCO World Heritage Site.

The reserve safeguards one of the most intact oceanic coral archipelago ecosystems left on Earth. It contains 14 known underwater seamounts, likely extinct volcanoes, along with other deep-sea habitats. Within its boundaries live about 800 known animal species, including roughly 200 types of coral, 500 fish species, 18 marine mammals, and 44 bird species. Though the entire area is comparable in size to the U.S. state of California, the total landmass amounts to just 25 square kilometers (9.7 square miles). To the north lies the U.S.-administered Pacific Islands Heritage Marine National Monument, currently the world’s largest designated MPA.

**History and administration**

The Republic of Kiribati, together with the nonprofit groups Conservation International and the New England Aquarium, established the Phoenix Island Protected Area Conservation Trust (PIPA Trust). In 2018, the New England Aquarium stepped down from the partnership, and the Aquarium of the Pacific joined the trust board. Management measures—covering zoning, permits, and other protections—are laid out in interim rules and a recently approved management plan.

Before full closure on January 1, 2015, the reserve’s administrators faced criticism over the amount of fishing allowed. Since that date, all commercial extractive activities, including tuna fishing, have been banned throughout the MPA. Only a small sustainable-use zone around Canton Island permits limited activities to support the local population. The PIPA Management Plan for 2015–2020, adopted after a Kiribati government decision in January 2014, imposes a total ban on commercial fishing within PIPA boundaries, including the territorial sea (out to 12 nautical miles) and all lagoons of the eight islands—Kanton, Manra, Rawaki, Birnie, McKean, Enderbury, Nikumaroro, and Orona—to protect marine and terrestrial species and their habitats. In November 2021, the Kiribati government announced it would terminate the protected area to boost tuna fishing, and the area officially reopened to commercial fishing in 2023.

**Natural heritage**

The PIPA includes three atolls with lagoons and perimeter coral reefs—Orona (Hull), Nikumaroro (Gardner), and Kanton (Aba-Riringa)—plus five low islands ringed by fringing reefs: Manra (Sydney), Rawaki (Phoenix), McKean, Birnie, and Enderbury. Two submerged reefs, Winslow and Carondelet, also lie within the zone. Seven main habitats are represented: island, lagoon, coral reef, deep reef, seamount, deep benthos, and open ocean.

Surveys conducted in 2000 (by Obura and colleagues) at Orona, Nikumaroro, Kanton, and the five low reef islands found the reefs in excellent health, free from the bleaching affecting other parts of the Pacific, with no signs of coral disease. Live Coral Cover (LCC) was moderate, ranging from 20% to 40%, and there was evidence of high physical breakage from wave energy on southern, eastern, and northern reefs, creating coral rubble in lagoons and at reef bases. In the lagoons, hard coral made up the dominant bottom cover (36.0%), followed by coralline red algae (18.0%), coral rubble (16.7%), turf and fleshy algae (11.6%), and the green macroalgae Halimeda (10.4%). The prevalence of coral and coralline algae points to healthy reef ecosystems dominated by calcifying organisms and active reef growth. Storm exposure is reflected in the dominance of storm-resistant encrusting and submassive coral forms on windward sites, their lower abundance on leeward sites, and a rise in delicate plate forms there, with fragile table and staghorn corals prevailing in protected lagoon areas. Coral species diversity was higher on the larger islands—Nikumaroro, Kanton, and Orona—suggesting that larger reef areas support more biodiversity. Carpeting soft corals (Sinularia and Lobophytum) were found on the bottoms of the Kanton and Orona lagoons, the only true lagoons in the Phoenix Islands.

Crown-of-thorns starfish (Acanthaster planci), cushion stars, and other coral predators like the corallivorous snail Drupella spp. are present, but no destructive outbreaks have been observed. Giant clams (Tridacna) occur in low numbers, including Tridacna squamosa and Tridacna maxima, but not Tridacna gigas.

The two submerged reefs, Winslow and Carondelet, along with at least 14 known seamounts and the open ocean and deep-sea habitats, are integral parts of PIPA. Scientific expeditions by the New England Aquarium, Boston University, Woods Hole Oceanographic Institution, Sea Education Association, and Schmidt Ocean Institute have found these seamounts rich in deep-water coral and biodiversity, supporting a variety of oceanic pelagic species. PIPA has been identified as an important area for such research.