Wasur National Park, Irian Jaya, Indonesia (Photograph by [WWF]-Canon/John Ratcliffe)

The Trans Fly Savanna and Grasslands ecoregion is one of the most extensive lowlands on the island of New Guinea. Its seasonally dry climate is unusual for the island of New Guinea and more like that of northern Australia. The habitats in this ecoregion are still relatively intact.

Location and General Description

This ecoregion is made up of the monsoonal savanna and grassland habitat along the southern coast of New Guinea, in both Indonesia and PNG. The climate of the ecoregion is strongly seasonal tropical dry, a climate that only this portion of New Guinea shares with much of Australia. Although the island of New Guinea is an active tectonic area with a complex geologic history, the geology of the West Papuan shelf, where this ecoregion is located, shows little folding, an indication of relative stability. The surface geology of the ecoregion consists of alluvium on active and relict alluvial plains and fans.

This ecoregion is composed primarily of grasslands, although almost a third of the region is savanna, and there are areas of dry evergreen forest. The pronounced seasonal rainfall, local relief, drainage, and the frequency of burning contribute to the variation in floristic structure. The savannas have strong structural and floristic affinities with those of northern Australia. The dominant trees in the savannas include Eucalyptus, Albizia, and Melaleuca. The Melaleuca forest dominates areas that are submerged in up to 1 meter of water during the wet season. An extensive belt of bamboo dominated by Schizistachyum occurs along the transitional stage between the adjoining forests and the savanna vegetation of the monsoonal area. The dune and beach communities in this ecoregion contain the uncommon Barringtonia asiatica.

Biodiversity Features

The overall richness and endemism of this ecoregion are low to moderate when compared with those of other ecoregions in Indo-Malaysia. There are forty-four mammal species in the ecoregion, including five species that are endemic or near endemic (Table 1). Three of these species, the Papuan planigale (Planigale novaeguineae), the bronze quoll (Dasyurus spartacus), and the dusky pademelon (Thylogale brunii) are considered vulnerable.

The ecoregion represents a portion of the Trans Fly Endemic Bird Area, EBA, which contains six restricted-range bird species. Five bird species are endemic or near endemic, including the vulnerable Fly River grassbird (Megalurus albolimbatus)(Table 2). Tonda Wildlife Management Area is a globally significant wintering ground for migratory waders and waterfowl from Australia and the Palearctic.

This ecoregion forms the heart of the Southern Fly Platform Centre of Plant Diversity. Its flora is closely related to that of Australia.

The Trans Fly region is also critical habitat for several species of endemic amphibians and reptiles and is the only location of the pitted turtle (Carettochelys insculpta), a unique species in its own family.

The key ecological process in savannas is fire. Although fires can occur during any rainless period, most savannas burn at the end of the dry season, when conditions are most favorable.

Current Status

Although the region is inhabited by a large number of sparsely distributed tribal groups, population pressure is low. Access from the outside of the ecoregion is poor, and there is generally little disturbance. More than 90 percent of the original habitat is still intact in this ecoregion. The five protected areas, well-distributed between Indonesia and PNG, cover 9,530 kilometers², representing about 36 percent of the ecoregion area (Table 3). Tonda, in PNG, and Wasur, in Indonesia, form a transboundary protected area complex that covers most of the coastal habitat.

Types and Severity of Threats

There is some threat on the Indonesian side from transmigration settlements, which result in increased hunting, wildlife trade, agricultural conversion, and unsustainable forestry practices. This would only be exacerbated by new roads, such as the planned Trans-Irian Highway.

The introduction of rusa deer (Cervus timorensis) from other areas of Indonesia has had serious impacts on the grasslands of this ecoregion.

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 savanna and grasslands in the Trans Fly region were placed in the Trans Fly Savanna and Grasslands under the Grasslands, Savannas, and Shrublands biome. This ecoregion also extends across the Arafura Sea to Australia, which was outside the region of analysis. 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