Islands off the northeast coast of mainland Papua

The Admiralty Islands Lowland Rain Forests [AA0101] contain several endemic species, yet the biodiversity of these islands is still poorly known. Commercial logging and conversion of forests to agriculture are the greatest threats to the ecoregion.

  • Scientific Code
  • Ecoregion Category
  • Size
    800 square miles
  • Status
  • Habitats

Location and General Description
The Admiralty Islands are located just north of PNG in the southwest Pacific Ocean and are often grouped together with New Britain and New Ireland to make up the Bismarck Archipelago. The Admiralty Islands form the political unit of Manus Province, PNG. Manus Province is the smallest province of PNG in both land area and population (32,713). The temperature of the Admiralty Islands varies little throughout the year, reaching daily highs of 30-32°C and 20-24°C at night. Average annual rainfall is 3,382 mm and is somewhat seasonal, with June-August being the wettest months (McAlpine et al. 1983).

Manus is the main island that reaches an elevation of 700 m, although there appears to be no discernible change in biota with altitude. Manus is volcanic in origin and probably broke through the ocean's surface in the late Miocene, 8-10 million years ago (Allison 1996). The substrate of the island is either directly volcanic or from uplifted coral limestone (Bleeker 1983). The vegetation of the Admiralty Islands is broadly described as lowland tropical rain forest. Johns (1993) highlighted the need to study the forests of central Manus, from Mt. Dremsel to the northern coast, and to protect the Calophyllum forests as an area of high biological importance.

Biodiversity Features
The Admiralty Islands are distinctive and contain endemic plant species because of their isolation from other landmasses. Characteristic species include tree species of the Calophyllum and Sararanga forests.

The Admiralty Islands contain several species with limited distribution, including five mammals species, two of which are found only in this ecoregion (table 1). Six bird species are endemic to the ecoregion, and seven more are near endemics (table 2). There are three birds listed by IUCN (1996) as vulnerable (Tyto manusi, Pitta superba, and Rhipidura semirubra). P. superba is quite beautiful and certainly a candidate for becoming a flagship species. T. manusi and R. semirubra are both forest-dwelling species that may be overlooked on Manus. Small islands off Manus are thought to be important to R. semirubra (Stattersfield et al. 1998).

Table 1. Endemic and Near-Endemic Mammal Species.

Family Species
Phalangeridae Spilocuscus kraemeri*
Pteropodidae Dobsonia anderseni
Pteropodidae Pteropus admiralitatum
Emballonuridae Emballonura serii
Muridae Melomys matambuai*

An asterisk signifies that the species' range is limited to this ecoregion.

Table 2. Endemic and Near-Endemic Bird Species.

Family Common Name Species
Megapodiidae Melanesian scrubfowl Megapodius eremita
Columbidae Yellow-bibbed fruit-dove Ptilinopus solomonensis
Columbidae Yellow-tinted imperial-pigeon Ducula subflavescens
Columbidae Pied cuckoo-dove Reinwardtoena browni
Psittacidae Meek's pygmy-parrot Micropsitta meeki
Tytonidae Manus owl Tyto manusi*
Strigidae Manus hawk-owl Ninox meeki*
Pittidae Black-headed pitta Pitta superba*
Monarchidae Manus monarch Monarcha infelix*
Rhipiduridae Manus fantail Rhipidura semirubra*
Zosteropidae Black-headed white-eye Zosterops hypoxanthus
Meliphagidae Ebony myzomela Myzomela pammelaena
Meliphagidae White-naped friarbird Philemon albitorques*

An asterisk signifies that the species' range is limited to this ecoregion.

The Admiralty Islands Lowland Rain Forests [AA0101] have an endemic Platymantis frog and four endemic lizards (Allison 1993). Additionally, the only land snail listed by IUCN, the green tree snail (Papustyla pulcherrima), is endemic to Manus (Parkinson et al. 1987). Johns (1993) estimates the total number of native plant species on Manus at 1,500.

Current Status
There is little information about the status of the Admiralty Islands Lowland Rain Forests [AA0101] ecoregion. Rannells (1995) stated that four-fifths of Manus is forested, although this figure includes both primary and secondary forest cover. The interior forests around Mt. Dremsel are still intact and have been listed as an important area of terrestrial biodiversity in PNG by Beehler (1993). The Mt. Dremsel forests are listed as a protected area by WCMC (1997), but the category of protected area has not been determined (table 3). Meanwhile, many of the smaller islands have been converted into coconut plantations (Rannells 1995).

Table 3. WCMC (1997) Protected Areas That Overlap with the Ecoregion.

Protected Area Area (km2) IUCN Category
Ndrolowa 60 VIII
Mt. Dremsel 240 ?
Total 300  

Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.

Types and Severity of Threats
Threats to the Admiralty Island moist forests include commercial timber extraction and destruction of habitat caused by shifting agriculture (Stattersfield et al. 1998).

Justification of Ecoregion Delineation
We delineated two ecoregions to represent the montane and lowland evergreen moist forests in the New Britain and New Ireland island complex; the New Britain-New Ireland Lowland Rain Forests [AA0111] and the New Britain-New Ireland Montane Rain Forests [AA0112]. The 1,000-m contour of the DEM (USGS 1996) was used as the transition between lowland and montane ecoregions. We placed the Admiralty Islands Lowland Rain Forests [AA0101] into a distinct ecoregion, following Stattersfield et al. (1998). MacKinnon (1997) combined these three ecoregions into a single subunit (P3p). Udvardy (1975) placed these ecoregions in the Papuan biogeographic province of the Oceanian Realm.

References for this ecoregion are currently consolidated in one document for the entire Indo-Pacific realm.
Indo-Pacific Reference List

Prepared by: John Lamoreux
Reviewed by:

This text was originally published in the book Terrestrial ecoregions of the Indo-Pacific: a conservation assessment from Island Press. This assessment offers an in-depth analysis of the biodiversity and conservation status of the Indo-Pacific's ecoregions.