Southeastern Asia: Island of Yapen in Indonesia

The Yapen Rain Forests [AA0108] are important for their two restricted-range bird species and unique limestone and ultramafic floras. Although almost one-third of the ecoregion is under some form of protection, the island is subject to population pressure. 

  • Scientific Code
  • Ecoregion Category
  • Size
    900 square miles
  • Status
  • Habitats

Location and General Description
This small ecoregion represents the lowland and montane rain forests of Yapen Island, 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 of low mountains of plutonic rock and limestone. The island extends to an elevation 1,430 m and is a land bridge island that was part of the New Guinea mainland during recent glacial periods.

The vegetation of Yapen Island is tropical lowland (alluvial and hill type) and montane forest.

Biodiversity Features
The overall richness and endemism of this ecoregion are low to moderate when compared with those of other ecoregions in Indo-Malaysia.

The mammal fauna consists of thirty-seven species, including a near endemic that Yapen shares with Biak and Numfoor islands (Yapen rat, Rattus jobiensis) (Flannery 1995; Flannery and Groves 1998; Bonaccorso et al., in press) (table 1).

Table 1. Endemic and Near-Endemic Mammal Species.

Family Species
Muridae Rattus jobiensis

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

Yapen is home to approximately 147 bird species (Beehler et al. 1986; Coates 1985), including two restricted-range species that qualify it as a Secondary EBA. These two near-endemic species (table 2), the spice imperial-pigeon (Ducula myristicivora) and the green-backed robin (Pachycephalopsis hattamensis), are also found on the mainland (Stattersfield et al. 1998).

Table 2. Endemic and Near-Endemic Bird Species.

Family Common Name Species
Columbidae Spice imperial-pigeon Ducula myristicivora
Eopsaltriidae Green-backed robin Pachycephalopsis hattamensis

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

Yapen and nearby Biak Island (part of Biak-Numfoor Rain Forests [AA0103] ecoregion) share one endemic butterfly species (Parsons 1999).

The island constitutes the Yapen Island Nature Reserve Centre of Plant Diversity (Davis et al. 1995). Several endemic plants have been collected, but the flora of the island is poorly known. The island contains significant limestone and ultramafic floras.

Current Status
Two protected areas, covering 790 km2, protect 32 percent of the island's ecosystems (MacKinnon 1997) (table 3).

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

Protected Area Area (km2) IUCN Category
Yapen Tengah 780 I
Inggresau 10 PRO
Total 790  

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

Types and Severity of Threats
The island is subject to population pressure, agricultural development, local sawmilling operations, and human-made fire. Only small, low-grade mineral deposits are present (R. Johns, pers. comm., 2000).

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 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.