Introduction

Past volcanic eruptions have been tremendous in the lowlands of New Britain and New Ireland. The New Britain city of Rabaul is surrounded by six volcanoes, and in September 1994 one of these forced the abandonment of the city. The numbers of animal endemics of the New Britain-New Ireland lowland rain forests are as remarkable as the volcanoes that mark the landscape. Commercial logging and conversion of forests to agriculture have altered much of the ecoregion.

Location and General Description

Near Kimbe, New Britain Island, Papua New Guinea. (Photograph by John Morrison)

The narrow Vitiaz Strait separates the Huon Peninsula of northeastern New Guinea from the island chain known as the Bismarck Archipelago, which is dominated by two islands: New Britain and New Ireland (both exceed 400 kilometers (km) in length). St. Matthias Islands, New Hanover, and many satellite islands are also part of the archipelago. The lowland rain forests ecoregion includes all of the Bismarck Archipelago below 1,000 meters (m). New Britain and New Ireland are both long and narrow and contain several mountain ranges that trap rainfall. The climate of the ecoregion is tropical wet but varies dramatically in amount of average annual rainfall from about 1,500 to more than 6,000 millimeters (mm) depending on the location.

Despite the proximity of the Bismarck Archipelago to New Guinea and the existence of small islands that appear to be the remnants of a land bridge, the island arc was never connected to the mainland. The islands breached the ocean surface in the late Miocene (8-10 million years ago) as the result of volcanic uplift, and many active volcanoes still exist (particularly on New Britain). Most of the islands are made up of volcanic (acidic) soils and limestone. Limestone makes up 30 percent of New Britain and nearly 40 percent of New Ireland, or the entire northern half.

Soils with limestone substrates are different from volcanic soils because the former lack nutrients and drain quickly. The vegetation of the Bismarcks therefore is unusual in that there appears to be no noticeable difference between the two main substrates in species composition. Overall diversity of tree species is not impressive when compared with that of mainland New Guinea. Major lowland rain forest tree genera include Pometia (Sapindaceae), Octomeles (Datiscaceae), Alstonia (Apocynaceae), Campnosperma (Anacardiaceae), Canarium (Burseraceae), Dracontomelon (Anacardiaceae), Pterocymbium (Sterculiaceae), Crytocarya (Lauraceae), Intsia (Leguminosae), Ficus (Moraceae), and Terminalia (Combretaceae). The vegetation of the Bismarck Archipelago is interesting for species that are not dominant. Araucaria hunsteinii and A. cunninghamii are two conifers that tower well above the lowland broadleaf forests in New Guinea but are not present in this ecoregion. Also, the dipterocarps that dominate much of Indonesia have only three species in New Guinea, and although one of these is reported from the Bismarcks, it has never been sufficiently documented. Other forest types in the lowlands include freshwater swamp and mangrove forests. The species composition of mangrove forests is specialized and occurs in zones beginning with Avicennia and Sonneratia spp. and moving inland to Rhizophora and Bruguiera spp., adding taller legumes and other species. Freshwater swamp forests are less specialized but include some notable species: Campnosperma brevipetiolata, Terminalia brassii, sago palm (Metroxylon sagu), and species of the genus Pandus. Limestone forests near the coast of southern New Ireland and along the coast and interior of New Britain are dominated by Vitex cofassus (Verbenaceae).

Biodiversity Features

East coast of New Ireland, Papua New Guinea. (Photograph by Jim Mori)

No comprehensive, modern botanical datasets exist for the Bismarcks, and much of the area is unknown in terms of biodiversity for any taxa. However, southern New Ireland has been surveyed botanically for a lowland site at about 300 m elevation in the Weitin Valley and two montane sites at 1,200 and 1,800 m. Findings from these surveys show that tree species diversity decreases steadily with increasing elevation, although the mid-elevational forests between 250 and 800 m that were not sampled by Takeuchi and Wiakabu are thought to be the most diverse. Foster found that even the dominant species of midelevational forests of southern New Ireland differ greatly with each ridge, although Pometia pinnata was overall the most abundant large species at lower elevations. Johns listed several regions within New Britain and New Ireland as areas of high biological importance based on their flora. Most of these regions are montane, but they include lowland portions: Lelet Plateau, southern Namatanai, Hans Meyer Range of New Ireland, and Willaumez Peninsula, Whiteman Range, Nakanai Mountains of New Britain.

There are forty-seven mammal species in the ecoregion. Most of these species are bats (thirty-six) in four families (Pteropodidae, Emballonuridae, Rhinolophidae, and Vespertilionidae), followed by rodent species (Muridae). Nine mammal species are near endemic to the ecoregion; none are strictly endemic (Table 1). Several species are listed as threatened (VU or higher) by IUCN: New Guinea pademelon (Thylogale brownii), Gilliard's flying-fox (Pteropus gilliardorum), large-eared sheathtail-bat (Emballonura dianae), Bismarck trumpet-eared bat (Kerivoula myrella), and New Britain water-rat (Hydromys neobrittanicus).

The ecoregion includes the St. Matthias Islands EBA and the lowland portions of the New Britain and New Ireland EBA. The lowland portions of New Britain and New Ireland contain nineteen endemic and thirty-six near-endemic species (Table 2). Two of these species are endemic to the St. Matthias Islands, one to New Hanover, one to Feni, ten to New Britain, and five to New Ireland. The rest are found on a combination of islands. Three of the restricted-range species are listed as threatened (VU or higher) by IUCN: Bismarck sparrowhawk (Accipiter brachyurus), yellow-legged pigeon (Columba pallidiceps), and Bismarck owl (Tyto aurantia). There is little doubt that the Bismarck Archipelago contains undescribed birds, but most of the areas for which information is lacking for birds lie outside the ecoregion at higher elevations.

Umboi Island is part of the ecoregion and lies between New Britain and mainland New Guinea. It is noteworthy for containing an amazing number of fruit bats (eight) and in having one of the most important waterbird sites in the Bismarcks.

Current Status

The ecoregion has been largely logged and replaced by forest plantation, copra, or oil palm production. Both provinces of New Britain (East and West) are among the leading producers of oil palm, copra, and timber. New Ireland is also a major producer of copra and timber. Much of the population of the Bismarcks consists of migrant workers. The province of West New Britain has the highest growth rate of any province, at 4.0 percent. As early as 1993, the few remaining natural portions of lowland forest on New Britain's north coast were thought to be in danger. Likewise, surveys conducted in 1994 predicted that without conservation action all of the lowland forest of New Ireland would be selectively logged within a few years. There is almost no primary forest left on the Saint Matthias Islands.

The current haphazard method of logging forests for any large, straight tree has many adverse effects. Beehler and Alonso highlighted three main considerations specifically for southern New Ireland, although they apply to the ecoregion as a whole:

• Species dependent on large trees, such as Blyth's hornbills, are unable to nest in logged areas.
• Non-native species (e.g., cats, feral dogs, Polynesian rats, and cane toads) are introduced into forests through logging operations and are often detrimental to native species.
• The long-term effects of removing large tree species may be detrimental to the regeneration of forests.

Feral pigs have been singled out as particularly harmful introduced species in New Ireland. Pigs eat certain plants selectively to the point that they have been nearly eliminated (e.g., a large Marattia fern).

Protected Areas

Two protected areas on New Britain contain nearly all of the lowland birds, including nesting sites of the Melanesian scrubfowl (Megapodius eremita): Pokili (98 square kilometers (km²)) and Garu Wildlife Management Areas (87 km²). Two other protected areas overlap with the ecoregion (Table 3). Several key areas of lowland forest remain located at the base of important montane regions. Protected areas connecting the lowland and montane forests are needed for conservation.

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. We used the 1,000 m contour of the digital elevation model (DEM) as the transition between lowland and montane ecoregions. We defined the Admiralty Islands lowland rain forests as a distinct ecoregion, following Stattersfield et al. MacKinnon combined these three ecoregions into a single subunit. 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