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Admiralty Islands lowland rain forests

Introduction

The Admiralty Islands Lowland Rain Forests 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.

Location and General Description

Manus Island, Admiralty Islands, Papua New Guinea. (Source: Atmospheric Radiation Measurement Program)

The Admiralty Islands are located just north of Papua New Guinea (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° Celsius and 20-24°C at night. Average annual rainfall is 3,382 millimeters (mm) and is somewhat seasonal, with June-August being the wettest months.

Manus is the main island that reaches an elevation of 700 meters, 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. The substrate of the island is either directly volcanic or from uplifted coral limestone. The vegetation of the Admiralty Islands is broadly described as lowland tropical rain forest. Johns 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 as vunerable (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.

The Admiralty Islands Lowland Rain Forests have an endemic Platymantis frog and four endemic lizards. Additionally, the only land snail listed by IUCN, the green tree snail (Papustyla pulcherrima), is endemic to Manus. Johns 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 ecoregion. Rannells 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. The Mt. Dremsel forests are listed as a protected area by WCMC, but the category of protected area has not been determined (Table 3). Meanwhile, many of the smaller islands have been converted into coconut plantations.

Types and Severity of Threats

Threats to the Admiralty Island moist forests include commercial timber extraction and destruction of habitat caused by shifting agriculture.

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 and the New Britain-New Ireland montane rain forests. The 1,000-meter contour of the DEM was used as the transition between lowland and montane ecoregions. We placed the Admiralty Islands Lowland Rain Forests into a distinct ecoregion, following Stattersfield et al. MacKinnon combined these three ecoregions into a single subunit (P3p). Udvardy placed these ecoregions in the Papuan biogeographic province of the Oceanian Realm.

Additional information on this ecoregion

• For a shorter summary of this entry, see the WWF WildWorld profile of this ecoregion.
• To see the species that live in this ecoregion, including images and threat levels, see the WWF Wildfinder description of this ecoregion.
• World Wildlife Fund Homepage