Location and General Description
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 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 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 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 (Mueller-Dombois and Fosberg 1998). 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) (Mueller-Dombois and Fosberg 1998). 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 (Mueller-Dombois and Fosberg 1998). Limestone forests near the coast of southern New Ireland and along the coast and interior of New Britain are dominated by Vitex cofassus (Verbenaceae) (Foster 2001).
No comprehensive, modern botanical datasets exist for the Bismarcks, and much of the area is unknown in terms of biodiversity for any taxa (Keast 1996; Sekhram and Miller 1994). 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 (Takeuchi and Wiakabu 2001). 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 2001). Foster (2001) 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 (1993) 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 (1996): 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).
Table 1. Endemic and Near-Endemic Mammal Species.
Pteropodidae Dobsonia anderseni
Pteropodidae Dobsonia praedatrix
Pteropodidae Melonycteris melanops
Pteropodidae Nyctimene major
Pteropodidae Pteropus admiralitatum
Pteropodidae Pteropus gilliardorum
Emballonuridae Emballonura serii
Muridae Hydromys neobritannicus
Muridae Uromys neobritannicus
An asterisk signifies that the species' range is limited to this ecoregion.
The ecoregion includes the St. Matthias Islands EBA and the lowland portions of the New Britain and New Ireland EBA (Stattersfield et al. 1998). 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 (1996): 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.
Table 2. Endemic and Near-Endemic Bird Species.
Family Common Name Species
Accipitridae Black honey-buzzard Henicopernis infuscatus*
Accipitridae Pied goshawk Accipiter albogularis
Accipitridae Slaty-mantled sparrowhawk Accipiter luteoschistaceus*
Accipitridae Bismarck sparrowhawk Accipiter brachyurus*
Megapodiidae Melanesian scrubfowl Megapodius eremita
Rallidae New Britain rail Gallirallus insignis
Columbidae Yellow-legged pigeon Columba pallidiceps
Columbidae Pied cuckoo-dove Reinwardtoena browni
Columbidae New Britain bronzewing Henicophaps foersteri*
Columbidae Yellow-bibbed fruit-dove Ptilinopus solomonensis
Columbidae Knob-billed fruit-dove Ptilinopus insolitus
Columbidae Red-knobbed imperial-pigeon Ducula rubricera
Columbidae Finsch's imperial-pigeon Ducula finschii
Columbidae Bismarck imperial-pigeon Ducula melanochroa
Columbidae Yellow-tinted imperial-pigeon Ducula subflavescens
Loriidae Cardinal lory Chalcopsitta cardinalis
Loriidae White-naped lory Lorius albidinuchus
Loriidae Red-chinned lorikeet Charmosyna rubrigularis
Cacatuidae Blue-eyed cockatoo Cacatua ophthalmica*
Psittacidae Finsch's pygmy-parrot Micropsitta finschii
Psittacidae Meek's pygmy-parrot Micropsitta meeki
Psittacidae Singing parrot Geoffroyus heteroclitus
Psittacidae Green-fronted hanging-parrot Loriculus tener*
Cuculidae Violaceous coucal Centropus violaceus
Cuculidae Pied coucal Centropus ateralbus
Tytonidae Bismarck owl Tyto aurantia
Strigidae Bismarck hawk-owl Ninox variegata*
Strigidae Russet hawk-owl Ninox odiosa
Apodidae Mayr's swiftlet Aerodramus orientalis
Alcedinidae Bismarck kingfisher Alcedo websteri*
Alcedinidae New Britain kingfisher Todirhamphus albonotatus*
Turdidae New Britain thrush Zoothera talaseae
Sylviidae Rusty thicketbird Megalurulus rubiginosus*
Monarchidae Black-tailed monarch Monarcha verticalis
Monarchidae White-breasted monarch Monarcha menckei*
Monarchidae Dull flycatcher Myiagra hebetior
Rhipiduridae Bismarck fantail Rhipidura dahli
Rhipiduridae Matthias fantail Rhipidura matthiae*
Dicaeidae Red-banded flowerpecker Dicaeum eximium
Zosteropidae Black-headed white-eye Zosterops hypoxanthus
Zosteropidae Louisiade white-eye Zosterops griseotinctus
Meliphagidae New Ireland myzomela Myzomela pulchella
Meliphagidae Ebony myzomela Myzomela pammelaena
Meliphagidae Black-bellied myzomela Myzomela erythromelas*
Meliphagidae Ashy myzomela Myzomela cineracea*
Meliphagidae Scarlet-bibbed myzomela Myzomela sclateri*
Meliphagidae New Britain friarbird Philemon cockerelli
Meliphagidae New Ireland friarbird Philemon eichhorni
Estrildidae Mottled munia Lonchura hunsteini*
Estrildidae New Ireland munia Lonchura forbesi*
Estrildidae New Hanover munia Lonchura nigerrima*
Estrildidae Bismarck munia Lonchura melaena
Sturnidae Atoll starling Aplonis feadensis
Dicruridae Ribbon-tailed drongo Dicrurus megarhynchus
Artamidae Bismarck woodswallow Artamus insignis*
An asterisk signifies that the species' range is limited to this ecoregion.
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 (Beehler 1993).
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 (Rannells 1995). 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 (Rannells 1995). As early as 1993, the few remaining natural portions of lowland forest on New Britain's north coast were thought to be in danger (Stattersfield et al. 1998). 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 (Beehler and Alonso 2001). There is almost no primary forest left on the St. Matthias Islands (Stattersfield et al. 1998).
The current haphazard method of logging forests for any large, straight tree has many adverse effects. Beehler and Alonso (in press) highlighted three main considerations specifically for southern New Ireland, although they apply to the ecoregion as a whole:
o Species dependent on large trees, such as Blyth's hornbills, are unable to nest in logged areas.
o 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.
o 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 (Foster 2001). Pigs eat certain plants selectively to the point that they have been nearly eliminated (e.g., a large Marattia fern) (Foster 2001).
Two protected areas on New Britain contain nearly all of the lowland birds, including nesting sites of the Melanesian scrubfowl (Megapodius eremita): Pokili (98 km2) and Garu Wildlife Management Areas (87 km2) (Stattersfield et al. 1998). 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.
Table 3. WCMC (1997) Protected Areas That Overlap with the Ecoregion.
Protected Area Area (km2) IUCN Category
Long Island 410 IV
Whiteman Mts. [AA0112] 1,690 ?
Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.
Types and Severity of Threats
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]. We used the 1,000-m contour of the DEM (USGS 1996) as the transition between lowland and montane ecoregions. We defined the Admiralty Islands Lowland Rain Forests [AA0101] as 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.
Prepared by: John Lamoreux