Southeastern Asia: Islands of Biak and Numfoor in

The Biak-Numfoor Rain Forests [AA0103], moderate-sized limestone islands guarding the entrance to Cenderawasih Bay, contain the most highly endemic avifauna of any single area in New Guinea. The islands have been heavily logged (Stattersfield et al. 1998).

  • Scientific Code
  • Ecoregion Category
  • Size
    1,100 square miles
  • Status
  • Habitats

Location and General Description
This small ecoregion is made up of the islands of Biak, Supiori (to 850 m), and Numfoor (to 204 m) (and small outlying islands) in Cenderawasih (Geelvink) Bay, approximately 50 km off the northwestern coast of Irian Jaya, Indonesia, on the island of New Guinea. The climate of the ecoregion is tropical wet, which is characteristic of this part of Melanesia, located in the western Pacific Ocean north of Australia (National Geographic Society 1999). The surface geology of this ecoregion consists mostly of extremely rugged limestone mountains, with an additional section of argillaceous sedimentary rock on Biak (Stattersfield et al. 1998; Petocz 1989). These oceanic islands, in contrast with nearby Yapen Island, have never been connected to the mainland, contributing to their high level of endemism.

The original lowland tropical wet evergreen forest of these islands was similar in structure and composition to the mainland lowland forest, which can be divided coarsely into alluvial and hill forest. Lowland alluvial forest has a multitiered and irregular canopy with many emergents. The forest understory contains a shrub and herb layer with a variety of climbers, epiphytes, and ferns (Petocz 1989). Palms may be common in the shrub layer. The somewhat lower-canopy, more closed lowland hill forest contains more open shrub layer but a denser herbaceous layer. Palms are fewer in number (Paijmans 1975). The dominant emergent trees on Biak and Numfoor include Pometia, Ficus, Alstonia, and Terminalia spp., and the lower-story trees consist of Garcinia, Diospyros, Myristica, Maniltoa, and Microcos spp. (Petocz 1989). Impressive coastal stands of Calophyllum are found in northern Biak (Beehler, pers. comm.).

Biodiversity Features
Overall richness and endemism are low to moderate when compared with those of other ecoregions in Indo-Malaysia, although for its size the ecoregion contains the most exclusively endemic avifauna of any single area in New Guinea (Stattersfield et al. 1998).

Twenty-nine mammal species are found in this ecoregion, including five endemic or near-endemic species (Wikramanyake et al. 2001; Flannery 1995; Flannery and Groves 1998) (table 1). The Biak bare-backed fruit bat (Dobsonia emersa) is considered vulnerable (IUCN 2000).

Table 1. Endemic and Near-Endemic Mammal Species.

Family Species
Petauridae Petaurus biacensis*
Pteropodidae Dobsonia emersa*
Muridae Rattus jobiensis
Muridae Uromys boeadii*
Muridae Uromys emmae*

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

The ecoregion harbors 107 bird species and matches the Geelvink Islands EBA (Stattersfield et al. 1998; Beehler et al. 1986; Coates 1985). The EBA contains fourteen restricted-range birds. The ecoregion contains thirteen endemic or near-endemic bird species (table 2). The Biak gerygone (Gerygone hypoxantha) and Biak monarch (Monarcha brehmii) are considered endangered, and the black-winged lory (Eos cyanogenia) is considered vulnerable (IUCN 2000).

Table 2. Endemic and Near-Endemic Bird Species.

Family Common Name Species
Megapodiidae Geelvink scrubfowl Megapodius geelvinkianus*
Psittacidae Geelvink pygmy-parrot Micropsitta geelvinkiana*
Loriidae Black-winged lory Eos cyanogenia*
Columbidae Spice imperial-pigeon Ducula myristicivora
Columbidae Yellow-bibbed fruit-dove Ptilinopus solomonensis
Cuculidae Biak coucal Centropus chalybeus*
Alcedinidae Biak paradise-kingfisher Tanysiptera riedelii*
Alcedinidae Numfoor paradise-kingfisher Tanysiptera carolinae*
Acanthizidae Biak gerygone Gerygone hypoxantha*
Monarchidae Biak monarch Monarcha brehmii*
Monarchidae Biak flycatcher Myiagra atra*
Sturnidae Long-tailed starling Aplonis magna*
Zosteropidae Biak white-eye Zosterops mysorensis*

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

This ecoregion is a center of butterfly endemicity in the New Guinea region, with eighteen endemic species (Parsons 1999).

The islands make up the Numfoor Island Nature Reserve-North Biak Island Nature Reserve Centre of Plant Diversity (Davis et al. 1995). Several endemic plants have been collected on the islands, but the flora is very poorly known (R. Johns, pers. comm., 2000).

Current Status
The human population in Biak Island is the highest among the offshore islands, and the island has already undergone a phase of logging operations; in fact, further logging is economically unfeasible. Logging and subsistence farming have damaged or destroyed much of the forest on Biak and Numfoor. Biak and Supiori are both transmigration sites as well. As a result of the damage and poor growing conditions of the raised limestone substrate, Biak's southern plains are now stunted woodland and arid scrub (Petocz 1989 and Bishop 1982 in Stattersfield et al. 1998).

The three small protected areas cover 344 km2, representing about 12 percent of the ecoregion (MacKinnon 1997) (table 3). The rugged topography of Supiori provides some degree of protection.

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

Protected Area Area (km2) IUCN Category
Pulau Supriori 270 I
Biak Utara 70 I
Pulau Biak 4 PRO
Total 344  

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

Types and Severity of Threats
If logging operations in other parts of Indonesia are hindered (for example, in the case of forest fires in Kalimantan), operations could shift to these islands to meet timber shortfalls. Continued subsistence farming to feed a growing population will further degrade the island's remaining habitats.

The birds that are limited to these islands are vulnerable simply because of the limited area of the islands. Hunting and trapping for trade are threats to several species (Stattersfield et al. 1998).

Justification of Ecoregion Delineation
Using Whitmore's (1984) map of the vegetation of Malesia and MacKinnon's (1997) reconstruction of the original vegetation, we delineated the large areas of distinct habitat types as ecoregions. Yapen and Biak islands, which MacKinnon combined within biounit P3c, were delineated as separate ecoregions; Yapen Rain Forests [AA0108] and Biak-Numfoor Rain Forests [AA0103], respectively, were based on recommendations by Bob Johns (vegetation) and Bruce Beehler (birds) and the patterns of mammal distribution. 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 Morrison
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.

For more general information on this ecoregion, go to the WildWorld version of this description.