Introduction

The Biak-Numfoor Rain Forests, 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.

Location and General Description

Satellite view of Numfoor and Biak islands (top center), Indonesia. (Photograph by USGS)

This small ecoregion is made up of the islands of Biak, Supiori (to 850 meters), and Numfoor (to 204 meters) (and small outlying islands) in Cenderawasih (Geelvink) Bay, approximately 50 kilometers 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. The surface geology of this ecoregion consists mostly of extremely rugged limestone mountains, with an additional section of argillaceous sedimentary rock on Biak. 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. 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. 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. Impressive coastal stands of Calophyllum are found in northern Biak.

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.

Twenty-nine mammal species are found in this ecoregion, including five endemic or near-endemic species (Table 1). The Biak bare-backed fruit bat (Dobsonia emersa) is considered vulnerable.

The ecoregion harbors 107 bird species and matches the Geelvink Islands EBA. 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.

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

The islands make up the Numfoor Island Nature Reserve-North Biak Island Nature Reserve Centre of Plant Diversity. Several endemic plants have been collected on the islands, but the flora is very poorly known.

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.

The three small protected areas cover 344 kilometers², representing about 12 percent of the ecoregion (Table 3). The rugged topography of Supiori provides some degree of protection.

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.

Justification of Ecoregion Delineation

Using Whitmore's map of the vegetation of Malesia and MacKinnon's 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 and Biak-Numfoor Rain Forests, respectively, were based on recommendations by Bob Johns (vegetation) and Bruce Beehler (birds) and the patterns of mammal distribution. 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

Further Reading

• Beehler, Bruce M. et al. Birds of Papua New Guinea. Princeton University Press; 1986. ISBN: 0691023948
• Paijmans, K. Ecological Notes on Sago in New Guinea. In: Stanton, W. R.; Flach, M., Editors. Sago: The Equatorial Swamp as a Natural Resource: Proceedings of the Second International Sago Symposium, Held in Kuala Lumpur, Malaysia, September 15-17, 1979. The Hague: Martinus Nijhoff Publishers; 1980: 9-12. (World Crops: Production, Utilization, and Description; v. 1). ISBN: 0643001387
• Villiers-Petocz on BioOne.
• Wikramanyake, Eric et al. 2001. Terrestrial Ecoregions of the Indo-Pacific: A Conservation Assessment. Ecoregions Set (all three). Washington, DC: Island Press. ISBN: 1559639237