Introduction

The Central Range Montane Rain Forests, which form the mountain spine of the island of New Guinea, contain more than 100 endemic vertebrates. The Central Ranges separate adjoining lowland on each side of the cordillera, and several constituent mountain ranges are isolated such that an extraordinary level of speciation has occurred within the Central Ranges. Some species are shared with outlying mountain ranges, but there are a significant number of locally endemic plants that are known only from a single mountain or mountain range.

Location and General Description

''Nothofagus'' forest, Irian Jaya, Indonesia. (Photograph by © WWF-Canon/John Ratcliffe)

This ecoregion is made up of the montane forests between 1,000 meters and 3,000 meters in the Central Cordillera of the island of New Guinea, in Irian Jaya, Indonesia and PNG, in the western Pacific Ocean north of Australia. The Central Cordillera is composed of a series of mountain ranges that are broadly grouped into the Snow Mountains in Irian Jaya, the Star Mountains in Irian Jaya and PNG, and the Central and Eastern Highlands in PNG. The climate of the ecoregion is tropical highland wet because of its elevation. The surface geology of the Central Cordillera is composed of metamorphic and intrusive igneous rocks. The metamorphic rocks were Cretaceous (100 m.y.) and Eocene (40 m.y.) ocean sediments that were folded between the Eocene and early Miocene Periods (20 m.y.). Pleistocene stratovolcanoes are also found in the Central Ranges.

There are three broad vegetation zones in the Central Ranges: lower montane forest, upper montane forest, and high mountain forest (although these are sometimes lumped into one lower montane rain forest). Lower montane forest continues up from the lowlands to approximately 2,500 meters. This zone is dominated by oaks, such as Castanopsis acuminatissima, elaeocarps, and laurels. Araucaria may form thick stands in lower areas. Nothofagus, sometimes in monotypic stands, is conspicuous in the moss-covered upper montane forest, which begins at about 1,500 meters. High mountain forest begins at approximately 2,500 meters and continues past the upper limits of the ecoregion, to 3,900 meters. The species-poor, high mountain forest includes conifers (Podocarpus, Dacrycarpus, Dacridium, Papuacedrus, Araucaria, and Libocedrus) and Myrtacae, with a thin canopy and prominent understory.

Biodiversity Features

The overall richness of this ecoregion is remarkable and ranges from moderate to high. The ecoregion contains some of the highest richness of vascular plants and herpetofauna in Indo-Malaysia and some of the highest endemism for mammals, birds, and vascular plants.

The mammalian fauna consists of a wide variety of tropical Australasian marsupials, including tree kangaroos. Ninety mammal species inhabit this ecoregion, of which an incredible forty-four are endemic or near endemic (Table 1). Four of these species are considered critically endangered: Bulmer's fruit-bat (Aproteles bulmerae), large leptomys (Leptomys elegans), eastern shrew-mouse (Pseudohydromys murinus), and lesser small-toothed rat (Macruromys elegans).

The avifauna of the ecoregion has a clear Australasian flavor, including representatives of several Australasian families such as Ptilonorhynchidae, Eopsaltridae, Meliphagidae, and Paradisaeidae. The ecoregion harbors 348 bird species, of which 55 are endemic or near endemic (Table 2). This ecoregion forms the majority of the Central Papuan mountains EBA, which contains fifty-three restricted-range bird species, eight of which are found in the adjacent Central Range sub-alpine grasslands, thirteen of which are shared with the adjacent Central Range sub-alpine grasslands, and seventeen of which are found nowhere else on Earth. Four of these species represent endemic genera. Archbold's bowerbird (Archboldia papuensis), ribbon-tailed astrapia (Astrapia mayeri), and the blue bird-of-paradise (Paradisaea rudolphi) are considered vulnerable.

Within this ecoregion, the Weyland Range (with nine endemic species) and the Hagen-Sepik-Wahgi Divide (with five endemic species) are both centers of butterfly endemism on the island of New Guinea.

Seven Centres of Plant Diversity are shared between this ecoregion and the adjacent Central Ranges sub-alpine grassland ecoregion. The Star Mountains-Telefomin-Tifalmin-Strickland Gorge CPD in PNG contains very rich (more than 3,000 vascular plant species) montane and high-altitude vegetation. The Hunstein Range-Bürgers Mountain-Schatteburg, Mt. Giluwe-Tari Gap-Doma Peaks CPD in PNG contains more than 2,500 vascular plant species and extensive stands of Agathis labillardieri and associated epiphytic flora. More than 3,000 vascular plant species are found in the Mt. Giluwe-Tari Gap-Doma Peaks CPD in PNG, including a unique Dacrydium swamp forest. The poorly known Kubor Ranges in PNG are a fragile ecosystem that probably contains many endemics on limestone and volcanic ash. The Bismarck Falls-Mt. Wilhelm-Mt. Otto-Schrader Range-Mt. Hellwig-Gahavisuka CPD has a wide variety of vegetation types and contains more than 5,000 vascular plant species. Important Araucaria cunninghamii, A. hunsteinii, and Castanopsis forests are found in the Mt. Michael-Okapa-Crater Mountain CPDs in PNG.

Current Status

The montane rain forests are generally undisturbed because of low population densities and traditional lifestyles. Some highland valleys are heavily populated, and this has resulted in local deforestation. A large and well-known hardrock mine is found in this ecoregion: the Freeport copper mine, located within the Lorentz Strict Nature Reserve in Irian Jaya. This is a large facility, and its location in a pristine area has caused concern about sedimentation and toxic runoff into adjacent stream and river systems. Petroleum extraction also occurs in Southern Highlands Province in PNG, but the environmental effects are minimal. More than half of the Lorentz Nature Reserve is under petroleum concessions.

Almost 20 percent of the ecoregion is covered by eleven protected areas (Table 3). The bulk of the protected area is in Irian Jaya, however. The largest protected area in the Central Ranges is the 21,500 km² Gunung Lorentz Nature Reserve in the Snow Mountains of Irian Jaya, although only 7,350 km² of the area is in this ecoregion.

Types and Severity of Threats

Logging concessions have been granted for large areas of the ecoregion. The threat of increased access (and subsequent hunting and illegal logging) via new roads is a significant concern. Mining poses threats in restricted locations.

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. The montane evergreen moist forests along the Central Cordillera, including the Snow Mountains, Star Mountains, Central Highlands, and Eastern Highlands, were placed in the Central Range Montane Rain Forests. This ecoregion roughly corresponds to MacKinnon's subunits P3g, P3h, and P3i. The moist forests in the southeastern peninsula were distinguished as the Southeastern Papuan Rain Forests. This ecoregion consists mostly of montane forests but also includes some lowland forests along the coasts and is roughly equivalent to MacKinnon's (1997) biounit P3n. We used the 1,000-meter contour from a DEM to define the montane-lowland transition. All along the Central Cordillera and in the Huon Peninsula, we separated the alpine habitat into a distinct (Central Range Sub-Alpine Grasslands) -ecoregion. Udvardy (1975) 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