Introduction

This ecoregion comprises the original "Spice Islands." The tropical islands that constitute the complex and mountainous terrain of the Halmahera Rain Forests are an important part of the region known as Wallacea, which contains a very distinctive fauna representing a mix of Asian and Australasian species. This small ecoregion contains an astounding twenty-six bird species, including four monotypic genera, which are found nowhere else in the world. Although there is some exploitation by logging and mining companies, extensive blocks of habitat still cover all the islands, and nearly 80 percent of its original forest still intact.

Location and General Description

Halmahera, Indonesia. (Photograph by Vincent Roelofs)

This ecoregion represents the moist forests on Halmahera, Morotai, Obi, Bacan, and the other nearby Maluku Islands in the northeastern Indonesian Archipelago. Based on the Köppen climate zone system, this ecoregion falls in the tropical wet climate zone. The geologic history of these islands is a very complex mixture of inner volcanic island arcs, outer volcanic island arcs, raised coral reefs, and fragments of continental crust. Halmahera is a product of a collision between two islands approximately 1-2 million years ago. The eastern half of the island was part of an outer arc on the Philippines tectonic plate and consists of sedimentary and igneous rocks. The western half of Halmahera and Morotai was part of an inner arc consisting of volcanic materials. Bacan is a mixture of volcanic inner island arc and some crustal materials.

The natural vegetation of these islands was tropical lowland evergreen and semi-evergreen forest. Most of the remaining habitat in this ecoregion is semi-evergreen rain forest and includes eight characteristic dipterocarp species: Anisoptera thurifera, Hopea gregaria, H. iriana, H. novoguineensis, Shorea assamica, S. montigena, S. selanica, and Vatica rassak. Volcanic soils and good aspect combine to produce almost optimal growth conditions. Most of the trees reach 30 meters or more and carry thick-stemmed lianas and woody and herbaceous epiphytes. Rattans that grow to 130 meters (m) and other epiphytes are common in old-growth forests. The most luxuriant rain forests occur in northwest Morotai and north Halmahera, as opposed to the south arm of Halmahera, which is in the rain shadow of north Halmahera and Bacan. Low, shrubby vegetation is found in poor soil conditions on patches of ultrabasic rocks.

Biodiversity Features

Overall diversity is low in this ecoregion, but overall endemism is moderate to high when compared with that of other ecoregions in Indo-Malaysia. This ecoregion falls within the Wallacean biogeographic zone, and thus exhibits a mixture of Asian and Australian fauna. Together with Seram, Buru, and the Banda Sea Islands, this island group forms part of a bioregion with perhaps the highest levels of bird endemism for its size anywhere in the world and the highest number of endemic birds of any area in Asia.

The mammal fauna is depauperate, containing only thirty-eight species with both Asian and Australasian affinities (cuscuses), but includes eight ecoregional endemics (Table 1). The Obi cuscus (Phalanger rothschildi) is considered vulnerable.

The ecoregion supports approximately 223 bird species, including 43 ecoregional endemism|species]] (Table 2). The ecoregion corresponds with the Northern Maluku Endemic Bird Area (EBA). There are four endemic monotypic genera: Habroptila, Melitorgrais, Lycocorax, and Semioptera. These species include the invisible rail (Habroptila wallacii), white-streaked friarbird (Melitograis gilolensis), paradise-crow (Lycocorax pyrrhopterus), and the standardwing (Semioptera wallacii). Of the forty-three restricted-range species found in this ecoregion (and EBA), an astounding twenty-six are found nowhere else in the world. Five vulnerable species, four of which are found nowhere else, are found in the ecoregion: invisible rail (Habroptila wallacii), caranculated fruit-dove (Ptilinopus granulifrons), chattering lory (Lorius garrulus), and white cockatoo (Cacatua alba).

The world's largest bee-the rare, 4-cm Wallace's giant bee Chalocodoma pluto-is also found on Bacan, Tidore, and Halmahera. Wallace discovered this species in 1858, and it was thought to be extinct until 1981, when it was recollected. This ecoregion also has conservation importance for butterflies and includes Troides aesacus, which may be the most primitive member of the T. priamus species group.

Current Status

The rich volcanic soils of Ternate, Tidore, and nearby islands have been aggressively cultivated for cloves and other spices for centuries. From the 1920s through the 1970s, commercial logging and enforced cultivation depleted the forests of Halmahera and Morotai. On Morotai, large tracts of lowland rain forest were cultivated with papaya (Carica papaya) during World War II. Currently, the wet evergreen lowland forests in the northwest of Halmahera are exploited by logging companies, primarily for the valuable damar trees (Agathis). The eastern forests are threatened by pulp plantations, especially using local transmigrants.

Extensive habitat blocks still cover all the islands, with only small areas near the coast cleared for human settlements. The seven protected areas cover 4,880 kilometers² (18 percent) of the ecoregion area (Table 3). Three protected areas are greater than 1,000 kilometers² in area, and the average size is 697 kilometers².

Types and Severity of Threats

With nearly 80 percent of its original forest still intact, the Halmahera Rain Forests ecoregion is largely free of intense habitat conversion threats. However, as the forests are lost on other Indonesian islands, there is an increasing potential for commercial forestry operations to move to Halmahera. A mining company, PT Halmahera Mineral (NHM), has already obtained an exploration license for Bacan and "neighboring islands" to look for gold and other minerals. A Canadian mining company has a license to mine nickel near Ake Tajawi on Halmahera.

Justification of Ecoregion Delineation

The Sula Islands were included within the Sulawesi Lowland Rain Forests, and the Aru islands in the Vogelkop-Aru Lowland Rain Forests. Buru Island, identified as a distinct subunit (13c) by MacKinnon and as an Endemic Bird Area (EBA) was delineated as a distinct ecoregion, the Buru Rain Forests. Seram, the larger island to the east of Buru, was also delineated as an ecoregion: Seram Rain Forests. The larger Halmahera Rain Forests ecoregion includes Obi Island, which MacKinnon recognized as a separate subunit (13b) from Halmahera Island (subunit 13a). We created the Banda Sea Islands Moist Deciduous Forests by combining the islands in the Kai and Tanimbar archipelagos, which were distinguished as a biogeographic unit by Monk et al. The primary vegetation on the islands in both these archipelagos is moist deciduous forests and semi-evergreen forests, whereas the vegetation in the other, nearby large islands (Seram and Aru) is evergreen rain forests.

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