Series of small islands off the eastern tip of Pap

The Louisiade Archipelago Rain Forests [AA0110] contain many endemic species of plants and animals, particularly birds, that help define it as a distinct unit. The main threats to the islands are logging, conversion of habitat into agricultural lands, and gold mining.

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

Location and General Description
The ecoregion includes a group island chain that lies off the southeastern tip of PNG. The first islands moving eastward in the chain are close to the mainland and include Sideia and Basilaki islands. Further east are the major islands in the archipelago: Misima, Sudest (or Tagula), and Rossel. Sudest Island is the largest (800 km2). All of the major islands of the Louisiades are volcanic, although there are numerous smaller islands that are coral formations.

The climate of the Louisiade Archipelago is moist tropical, and the vegetation consists of rain forest, although some of the low-lying smaller islands receive less rainfall. Paijmans (1975) categorized most of the ecoregion as small crowned lowland hill forest. This type of forest is shorter (20-30 m in height) than that found in other areas in New Guinea because of either poor soil conditions or less rainfall. The former is probably the case, as Johns (1993) remarked on the very poor soils of Rossel and Misima. Tree genera in pure forest stands include Casuarina, Castanopsis, and Hopea. Paijames (1975) listed mixed forest genera for low rainfall areas as Pometia, Canarium, Anisoptera, Cryptocarya, Terminalia, Syzygium, Ficus, and Celtis.

Biodiversity Features
The ecoregion is distinctive botanically. Johns (1993) noted that the Louisiade Archipelago has long been known as an area with many endemic species. Misima stands out for having several ant plant species (Rubiaceae) and an endemic Pandanus. Rossel contains an undescribed Diospyros species and several Hopea species. Perhaps most impressive is that Rossel also contains an undescribed genus in the family Burseraceae. The archipelago is also noteworthy for its endemic reptiles and amphibians. Allison (1993) listed eight total endemics, including five frogs and two lizards.

There are twenty-four mammal species in the Louisiade Archipelago rain forests. Most of these species are bats (eighteen) in three families (Pteropodidae, Rhinolophidae, and Vespertilionidae), followed by rodent species (Muridae). No mammal species are endemic to the Louisiade Archipelago, but three species are near endemics (table 1). St. Aignan's trumpet-eared bat (Kerivoula agnella) is the only IUCN (1996) threatened (VU) mammal in the ecoregion and is recorded from Misima and Sudest.

Table 1. Endemic and Near-Endemic Mammal Species.

Family Species
Pteropodidae Nyctimene major
Pteropodidae Pteropus pannietensis
Vespertilionidae Kerivoula agnella

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

For the most part, the ecoregion matches the Louisiade Archipelago EBA (Stattersfield et al. 1998). There are five endemic bird species in the ecoregion and two near endemics (table 2). Stattersfield et al. (1998) stated that very little is known about any of these birds, and four of the seven species are listed as data deficient (DD) by IUCN (1996), meaning that a category of threat cannot be determined.

Table 2. Endemic and Near-Endemic Bird Species.

Family Common Name Species
Meliphagidae White-chinned myzomela Myzomela albigula*
Meliphagidae Tagula honeyeater Meliphaga vicina*
Pachycephalida White-bellied whistler Pachycephala leucogastra
Cracticidae Tagula butcherbird Cracticus louisiadensis*
Zosteropidae White-throated white-eye Zosterops meeki*
Zosteropidae Louisiade white-eye Zosterops griseotinctus
Dicaeidae Louisiade flowerpecker Dicaeum nitidum*

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

Current Status
Vegetation maps show that as early as a quarter century ago the habitats of Deboyne, northwest Sudest Island, and nearby Pana Tinani were all degraded as either anthropogenic grasslands or agricultural lands (Paijames 1975). Allison (1993) noted that much of the forest is gone from Sudest and that the forests around Mt. Riu must be protected if many of the endemic species of the Louisiades are to remain. Beehler (1993) also stated that the forests from Mt. Riu eastward are very important to the survival of the Tagula honeyeater and the Tagula butcherbird. Gold mining has been very destructive on Misima (Johns 1993). There are no protected areas in the ecoregion.

Types and Severity of Threats
The main threats to the ecoregion are logging, conversion of habitat into agricultural lands, and gold mining.

Justification of Ecoregion Delineation
The Trobriand Islands Rain Forests [AA0125] and Louisiade Archipelago Rain Forests [AA0110] were made distinct ecoregions based on Stattersfield et al. (1998). MacKinnon (1997) placed these two ecoregions together into subunit P3o. 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 Lamoreux
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.