Location: 24 degrees 40 minutes S, 124 degrees 47 minutes W; in the central South Pacific, 472 km east of Pitcairn Island and 1,336 km WNW of Easter Island.

Area: Land area, 70 ha; land, reef and lagoon, 320 ha.

Altitude: Sea level to 4 m.

Overview: A seldom visited, exceptionally undisturbed atoll; the easternmost atoll in the Indo-Pacific biogeographic region, possessing a pure, though impoverished, Polynesian biota.

Physical features: A small coral atoll comprising a main island (Acadia) and three small islets or “motu” (Edwards, Pandora and Westward) encircling a lagoon approximately 1.5 km in diameter. The islands are composed of coral rubble, echinoid remains and dead shells. Acadia is largely surrounded by reef flats, the reef to the northwest consisting for the most part of a somewhat uneven reef pavement flat. Small channels between the lagoon and the ocean are found at the northernmost extension of Westward and western end of Acadia, but these have little influence on water exchange within the lagoon. The greatest seaward extension of the reef is at the southwest, where the shelf extends 270 m offshore to a depth of 30 m. There is a regular semi-diurnal tide. Salinity in the lagoon is about 38 p.p.t., and water temperature averages 26.5 degrees C.

Ecological features: The reef flats are generally covered by a thin layer of sand and fine algal growth. There is a fair amount of coral cover in the lagoon, the dominant genera being Montipora and Astreopora. The lagoon floor between the patch reefs consists of fine white sand. The outer reef has fairly good coral cover, with very high cover (as much as 50%) recorded in deep water. Corals of the genera Acropora and Montipora dominate. Terrestrial vegetation is confined to Acadia, and comprises an impoverished atoll scrub dominated by Tournefortia. There is also one Pemphis bush.

Land tenure: State owned (Crown Land).

Conservation measures taken: None. Considerable protection is afforded by the extreme remoteness of the island.

Conservation measures proposed: Ducie was proposed for listing as an “Island for Science” in 1969 (Elliot, 1973). Hepburn et al. (1992) have recommended that the entire atoll be designated as a Ramsar Site.

Land use: The atoll is visited very infrequently (less than five times a year) by passing yachts and cruise ships, but because of the difficulty in landing, few people set foot on the islands.

Disturbances and threats: Polynesian Rats (Rattus exulans) are present, but apparently cause relatively little predation on nesting sea-birds. There is a possibility that the crews of passing fishing boats occasionally land on the islands to harvest seabirds. In 1970, there was evidence of a relatively recent mass mortality of corals, the cause of which was not identified, although a sudden drop in water temperature was postulated. Some recovery seemed to have occurred by 1987 (UNEP/IUCN, 1998).

Hydrological and biophysical values: Not known.

Social and cultural values: Limited value for tourism. 

Noteworthy fauna: Atoll is particularly important for its large breeding populations of sea-birds. The island supports probably the world’s largest breeding colony of Murphy’s Petrels (Pterodroma ultima), with around 250,000 pairs, as well as about 20,000 pairs of Kermadec Petrels (P. Neglecta) and 20,000 pairs of Herald Petrels (P. heraldica). Other breeding seabirds include Christmas Shearwater (Puffinus nativitatis), Red-tailed Tropicbird (Phaethon rubricauda), boobies (Sula spp.), Great Frigatebird (Fregata minor), Sooty Tern (Sterna fuscata), Brown Noddy (Anous stolidus), Blue-grey Noddy (Procelsterna cerulea) and Fairy Tern (Gygis alba). Three species of migrant shorebirds have been reported, Wandering Tattler (Heteroscelus incanus), Bristle-thighed Curlew (Numenius tabitiensis) and Sanderling (Calidris alba), but numbers are generally low (less than 20). There are no land-birds, and the only mammal present is the Polynesian Rat (Rattus exulans). Two species of land hermit crab (Coenobita spp.) Have been recorded. The fish fauna is considered to be impoverished; only 138 species were recorded by Rehder and Randall (1975), with 15 of these being confined to southeastern Oceania. However, the island has a reputation for its large shark population. Insects, crustaceans, echinoderms and corals are listed by Rehder and Randall (1975).

Noteworthy flora: The island is exceptional for the paucity of its flora; only two species of vascular plants are known.

Scientific research and facilities: The island was visited by the Whitney South Sea Expedition in 1922, by the 1970-71 National Geographic Society-Oceanic Institute Expedition to Southeast Oceania, and by Operation Raleigh in 1987. Scientists from the Pitcairn Islands Scientific Expedition (based on Henderson) visited the island at approximately three-monthly intervals during 1991.

Recreation and tourism: The island has some value for “high-quality” tourism, e.g. for passengers from Society Expedition cruise ships.

Management authority and jurisdiction: Pitcairn Islands Council in conjunction with the British Consulate-General in Auckland (New Zealand).

References: Dahl (1980, 1986); Elliot (1973); Hepburn et al. (1992); Rehder & Randall (1975); UNEP/IUCN (1988).

Reasons for inclusion: 1a, 2a, 2c. An exceptionally undisturbed atoll ecosystem and one that, by virtue of its geographical location, is likely to remain so.

Source: M. de L. Brooke and references.

Location: 24 degrees 22 minutes S, 128 degrees 20 minutes W; in the central South Pacific, 200 km ENE of Pitcairn Island.

Area: Land area, 3,700 ha; area of beaches and reef flats unknown.

Altitude: Sea level to 33 m.

Overview: One of the least disturbed raised coral atolls in the world, with its terrestrial ecosystems virtually intact. The island supports a large breeding population of seabirds, and has four endemic land-birds, one of which is a flightless rail. The beaches and reef flats are important for wintering Bristle-thighed Curlews (Numenius tahitiensis).

Physical features: A raised coral atoll composed of coralline limestone, with a slight depression in the centre considered to be an uplifted lagoon. The island is arid, with no surface fresh water except for some drippings in caves, a few very small fresh to brackish pools at the South End (which appears to be rain-fed and become increasingly saline through evaporation and salt-spray) and small amounts of rainwater trapped in vegetation, such as at the base of Asplenium leaves. Fresh or brackish springs have been located below high tide level at North Beach and Northwest Beach. No readily available source of groundwater has yet been located. The surface of the island is largely reef rubble, with some areas of dissected limestone, especially around the periphery. The island is surrounded by steep cliffs of bare limestone. There is a fringing reef averaging 50-100 m in width around most of the island except in the extreme south and west. In three places, North Beach, Northwest Beach and East Beach, the reef extends up to 200 m offshore, and is backed by a wide, gently shelving coral sand beach over bedrock which is partly exposed. The reef off the East Beach has a poorly developed lagoon; those off the North and Northwest beaches are seawardly sloping reef platforms without a well-defined reef crest. There are two narrow channels through the reef on the north and northwest coasts. Tides are semi-diurnal, with a tidal range at spring tides of about one metre.

The island lies in the Southwest Trades, and probably has a mean annual rainfall of about 1,500 mm. The recorded rainfall during the period February 1991 to January 1992 was 1,620 mm.

Ecological features: Coral cover on the fringing reef is about 5%, dominated by Pocillopora with Millepora becoming dominant at depths greater than 7 m. The top of the island is densely vegetated with tangled scrub and scrub forest, 5-10 m tall, except in the central part of the depression, which is more sparsely vegetated. The tallest trees are screwpine Pandanus tectorius; other trees include the endemic sandalwood Santalum hendersonense, Myrsine hoskau, Celtis paniculata var. viridis, and two shrubby endemic varieties of Bidens hendersonensis. Some coconuts have been planted near the main landing sites, close to which the Pitcairners harvest hardwoods. Otherwise the vegetation is largely undisturbed.

Land tenure: State owned (Crown Land).

Conservation measures taken: Henderson Island has not been declared a protected area as such, although it receives de facto protection from its isolation and various restrictions on possession, occupation and transference of land applied under the Lands and Administration of Estates Ordinance (IUCN, 1991). Access to the island requires a license issued by the Governor following approval by the Pitcairn Islands Council. Henderson Island was inscribed as a World Heritage Site under the Unesco World Heritage Convention in 1988, but no formal management of the site has yet been undertaken. The UK Joint Nature Conservation Committee has recently commissioned the production of a draft management plan for the World Heritage Site.

Conservation measures proposed: Henderson was proposed for listing as an “Island for Science” in 1969 (Elliot, 1973), and recommended as a reserve by the IUCN Threatened Plants Committee (Dahl, 1980). It has also been suggested that the island be declared a Biosphere Reserve under Unesco’s Man and the Biosphere Programme. The draft management plan (Hepburn, in prep) recommends that Local Government Regulations be amended to provide appropriate protection to the World Heritage Site. Hepburn et al. (1992) have recommended that the coastal and inshore marine zones of the island be designated as a Ramsar Site.

Land use: Henderson was apparently colonized by Polynesians between 800 and 1600 AD, but has remained uninhabited in modern times. Pitcairn islanders visit the island roughly once a year, normally for one day, to cut and remove timber (Cordia subcordata and Thespesia populnea) from the woodlands behind the beach. The wood is used for carving handicrafts for sale to visitors. The island is occasionally visited by passing yachts and natural history cruise ships.

Disturbances and threats: Goats and pigs were intorduced to the island in the early part of this century but did not survive. Introduced Polynesian Rats (Rattus exulans) are, however, still present, and cause devastating predation on the chicks of three species of gadfly petrel, Pterodroma neglects, P. heraldica and P. ultima. The terrestrial vegetation is still largely pristine, with very few exotics, although there are two substantial coconut groves at the principal landing sites. A proposal in 1982/83 by an American millionaire to settle on Henderson was given serious consideration by the British authorities. The development would have included clearance of forest in order to graze cattle, the building of an airfield, and the introduction of other farm stock. The proposal was finally rejected on environmental and technical grounds. There has been some anchor damage to the coral reefs. Reef blasting to improve the landing passage would be detrimental, as would the introduction of any alien plants or animals.

Hydrological and biophysical values: None known. 

Social and cultural values: Miro trees (Thespesia populnea) and Toa (Cordia subcordata) are of value to the Pitcairn islanders as a source of wood for carving.

Noteworthy fauna: The beaches and reef flats are used by a wintering population of some 40-50 Bristle-thighed Curlews (Numenius tahitiensis), most of which arrive in early September and depart in April. Small numbers of Wandering Tattlers (Heteroscelus incanus), and Sanderlings (Calidris alba), also occur on the beaches. The island is very important for its large breeding population of seabirds, estimated at 50,000-80,000 pairs. These include 10,000-20,000 pairs of Kermadee Petrels (Ptedodroma neglecta), 30,000 pairs of Herald Petrels (P. heraldica), several thousand pairs of Murphy’s Petrels (P. ultima), 200-300 pairs of Red-tailed Tropicbirds (Phaethon rubricauda), 50-60 pairs of Masked Boobies (Sula dactylatra), a few hundred pairs of Red-footed Boobies (S. Sula), 100 pairs of Great Frigatebirds (Fregata minor), 100 pairs of Brown Noddies (Anous stolidus), small numbers of Black Noddies (A. minutus), possibly ten pairs of Blue-grey Noddies (Procelsterna cerulea), and very large numbers of Fairy Terns (Gygis alba), (Hepburn, in prep). The island has three endemic species of land-birds, the Henderson Island Rail (Porzana (Nesophylax) atra), Henderson Island Fruit-Dove (Ptilinopus insularis), and Stephen’s Lorikeet (Vini stepheni), as well as an endemic subspecies of the Pitcairn Reed Warbler (Acrocephalus vaughani taiti). The rail is primarily a forest bird, foraging in the leaf litter for insects and molluscs. Although still common, this flightless and tame species would be at considerable risk from introduced predators and is therefore listed as threatened in the IUCN Red Data Book (Collar & Andrew, 1988). The total population was estimated at about 4,700 pairs in 1991/92(Hepburn, in prep). The lorikeet appears to be rather uncommon, and is also listed as threatened.

The only mammal present is the introduced Polynesian Rat (Rattus exulans). Green Turtles (Chelonia mydas) nest on East Beach, where up to 30 scrapes were reported in 1991/92. There is one species of skink (Emoia cyanura), which appears to be abundant throughout the island, and two species of gecko, one of which (as yet unidentified) may be endemic. Coconut Crabs (Birgus latro) are present. Possibly all of the island’s 14 or so species of small land snail and about 30% of the island’s 170 species of insect are endemic. The proportion of endemic species in some other invertebrate groups is given by Hepburn (in prep). The coral reefs support a diverse mariena fauna, although fish species are relatively few (UNEP/IUCN, 1988).

Noteworthy flora: Henderson supports a rich and almost undisturbed terrestrial flora, with 72 species of vascular plants, ten of which are endemic to the island. The two endemic varieties of the shrub Bidens hendersonense are of particular botanical interest.

Scientific research and facilities: A number of scientific expeditions have visited the island, including the Whitney South Sea Expedition in 1922 and the Mangarevan Expedition in 1934. A multi-disciplinary scientific expedition (the Pitcairn Islands Scientific Expedition) was based on the island from January 1991 to March 1992. The major results of this expedition are likely to be available in 1994.

Recreation and tourism: The island is occasionally visited by passengers from cruise ships, with groups of up to 100 people landing at a time.

Management authority and jurisdiction: Pitcairn Islands Council in conjunction with the British Consulate-General in Auckland (New Zealand).

References: Collar & Andrew (1988); Dahl (1980, 1986); Elliot (19730; Hay (1985); Hepburn (in prep); Hepburn et al. (1992; IUCN (1991); St. John & Philipson (1962); UNEP/IUCN (1998).

Reasons for inclusion: 1a, 2a, 2b, 2c, 2d. Henderson is of outstanding value as the world’s best remaining example of a raised coral atoll ecosystem. The reef flats and beaches support an internationally significant wintering population of Bristle-thighed Curlews.

Source: J.R. Setterfield, I. Hepburn and references.

Location: 23 degrees 56 minutes S, 130 degrees 44 minutes W; in the central South Pacific, 120 km northwest of Pitcairn.

Area: Land area, 65 ha; land, reef and lagoon, 1,600 ha.

Altitude: Sea level to 3.6 m.

Overview: A seldom visited, ecologically undisturbed atoll with a significant wintering population of Bistle-thighed Curlews (Numenius tahitiensis) and large breeding populations of seabirds.

Physical features: A low coral atoll comprising a central islet surrounded by a lagoon, mostly 3-6 m in depth, which in turn is surrounded by a fringing reef within which there are many smaller reefs. An interesting northward shift of the islet, the result of erosion and deposition under the influence of the prevailing Southeast Trades, has taken place in the past 150 years.

Ecological features: Montipora is the dominant coral genus, with Acropora also common. Other genera recorded are Pocillopora, Psammocora, Pavona, Porites, Cyphastrea, Plesiastrea and Montastrea. The terrestial vegetation is atoll forest and scrub with a few coconuts.

Land tenure: State owned (Crown Land).

Conservation measures taken: None. Considerable protection is afforded by the extreme remoteness of the island.

Conservation measures proposed: Oeno was proposed for listing as an “Island for Science” in 1969 (Elliot, 1973). Hepburn et al. (1992) has recommended that the entire atoll be designated as a Ramsar Site. Hepburn (in prep) recommends that the island be made rat-free to provide a secure nesting site for seabirds, especially gadfly petrels (Pterodroma spp.) which are heavily predated by Polynesian Rats on Henderson.

Land use: Uninhabited, but usually visited once a year (and sometimes more) by about 30 Pitcairn islanders for a fishing holiday. Occasionally visited by the crews of passing yachts (about five a year).

Possible changes in land use: Various persons in Mangareva (Gambier Islands, French Polynesia) have expressed interest in the establishment of black pearl oyster farms in the lagoon.

Disturbances and threats: Introduced Polynesian Rats (Rattus exulans) are present. The disturbance associated with the proposed establishment of oyster farms might be detrimental to the seabird populations, especially if the latter were harvested. Fishing in the lagoon and the harvesting of shells could also be damaging to the lagoon ecosystem. The Pitcairn islanders have recently expressed a desire to plant coconuts and other exotic species on the island.

Hydrological and biophysical values: None known. 

Social and cultural values: A "holiday resort” for Pitcairn islanders.

Noteworthy fauna: The island supports a significant wintering population of Bristle-thighed Curlews b(Numenius tahitiensis) (about 100 individuals), and a large breeding population of seabirds, including about 8,000-10,000 pairs of Murphy’s Petrels (Pterodroma ultima), 250 pairs of Red-footed Boobies Sula sula), 250 pairs of Masked Boobies (S. dactylatra) and 100 pairs of Great Frigatebirds (Fregata minor). Coconut Crabs (Birgus latro) occur on the island, and the undisturbed lagoon supports prolific fish populations.

Noteworthy flora: There are no endemic species of plants on the island, but this constitutes the extreme southeastern limit for several species (eg. Hedyotis romanzoffiensis). Tournefortia argentea grows to the exceptional height of 8 m.

Scientific research and facilities: The island was briefly visited by a Smithsonian Expedition in 1987. Scientists from the Pitcairn Islands Scientific Expedition (based on Henderson) visited the island at approximately three-monthly intervals during 1991 and early 1992.

Recreation and tourism: Roughly once a year, the island is visited by about 30 Pitcairn islanders for a holiday of one week.

Management authority and jurisdiction: Pitcairn Islands Council in conjunction with the British Consulate-General in Auckland (New Zealand).

References: Dahl (1980, 1986); Elliot (1973); Hepburn (in prep); Hepburn et al. (1992); Philipson & St. John (1960); UNEP/IUCN (1988); Williams (1960).

Reasons for inclusion: 1a, 2a, 2c. One of the least disturbed atolls in southeastern Polynesia, with an internationally important wintering population of Bristle-thighed Curlews.

Source: M. de L. Brooke.