Location and General Description
This ecoregion represents the semi-evergreen dry forests of Timor, Wetar, and some smaller islands in the provinces of Nusa Tenggara and Maluku in the eastern Indonesian Archipelago. This ecoregion has a dry climate, with the most xeric being the mountains of Timor. Moa, in the Leti Islands, receives an average of 1,329 mm rainfall spread over just sixty-six days of the year. Based on the Köppen climate zone system, this ecoregion falls in the tropical dry climate zone (National Geographic Society 1999). The geology of the islands is a combination of inner and outer volcanic island arcs. Wetar, Romang, Damar, and the Banda Islands are part of the inner arc, and Timor, the Leti Islands, Sermata, and Babar are part of the outer arc. The inner arc islands are a result of the subduction and partial melting of the Australian tectonic plate below the Eurasian plate. With the exception of Wetar, the inner arc islands represent young volcanoes that have coalesced with lava and sediment. The basement rock of the outer islands, on the other hand, is composed of actual continental margin from the Australian plate that has not been subducted. These outer islands are less than 4 million years old. The resulting surface geology consists of complex sedimentary and metamorphic rocks: uplifted coral reefs over complex basement rocks (Monk et al. 1997).
The forest types in the ecoregion are dry deciduous, dry evergreen, and thorn forests. Below 1,000 m the common tree species include Sterculia foetida and Calophyllum teysmannii (both of which produce oil-bearing seeds) and Aleurites moluccana. The lowland monsoon forests are dominated by Pterocarpus indicus, especially in the lowland monsoon forest remnants of West Timor and in the well-drained, dry soils north of Oebelo on the Bena coastal plain in south Timor (Monk et al. 1997). Semi-evergreen rain forest is found on southern hill slopes at Buraen, which are kept moist by southeast trade winds, and on the Damar Islands (Monk et al. 1997). East Timor's few remaining forest patches contain the last natural stands of Eucalyptus urophylla (now widely used in plantations) and Santalum album, the sandalwood tree (Whitten and Whitten 1992). The shrub layer in these forests includes Verbenaceae, Rubiaceae, and Euphorbiaceae, and the herbs include Acanthaceae, Tacca palmata, the root parasite Balanophora fungosa, and ground orchids such as Corymborkis (Monk et al. 1997). Four types of savanna are found here, each characterized by palm, Eucalyptus, Acacia spp., and Casuarina spp. On Timor's larger coastal plains, the vegetation ranges from grassland to open stands of deciduous trees, with increasing forest cover toward the moister southern mountains.
This ecoregion has the greatest number of bird species of any tropical dry forest ecoregion in the Indo-Pacific region. Because of the long isolation with the mainland communities, there are several endemic species from several taxonomic groups.
The ecoregion has thirty-eight mammal species, five of which are endemic or near endemic (table 1). Both Asian species and an Australasian cuscus (Phalanger orientalis timorensis) are found on the islands. Crocidura tenuis (Soricidae), possibly introduced by man, and the Flores giant rat (Papagomys armandvillei) are considered vulnerable (IUCN 2000).
Table 1. Endemic and Near-Endemic Mammal Species.
The bird fauna consists of about 229 species. The bird fauna also represents a mix of mostly Asian species with some Australasian birds. Endemism is extremely high for these islands, with thirty-five species that are endemic or near endemic (table 2). The ecoregion encompasses with the Timor and Wetar EBA (Stattersfield et al. 1998). Thirty-five restricted-range bird species are found in the Timor and Wetar EBA, twenty-three of which are found nowhere else on Earth. Five of these species are considered vulnerable: black cuckoo-dove (Turacoena modesta), Wetar ground-dove (Gallicolumba hoedtii), Timor green-pigeon (Treron psittacea), Timor imperial-pigeon (Ducula cineracea), and iris lorikeet (Psitteuteles iris).
Table 2. Endemic and Near-Endemic Bird Species.
Timor also harbors the endemic and rare Timor python (Python timoriensis) (Whitten and Whitten 1992).Current Status
Other than one remaining large block of forest near the center of Timor Island, this ecoregion contains only fragments of natural habitat. Nearly two-thirds of the original extent of forest has been cleared, mostly for agriculture. Most of the original monsoon forest on these islands has been replaced by savanna and grassland. On East Timor, the south escarpment of the Fuiloro limestone plateau originally was covered by primary rain forest, but in the 1950s this area was degraded to secondary forest. Wetar is threatened by poorly managed gold mines that have been passed from company to company, causing major environmental damage. There are twenty-four protected areas that include roughly 10 percent (3,661 km2) of the ecoregion area, but all are small, with the average size being only 152 km2 (Monk et al. 1997) (table 3).
Table 3. WCMC (1997) Protected Areas That Overlap with the Ecoregion.
Deforestation is occurring very rapidly as people burn the forests for hunting, shifting cultivation, and fodder production (Whitten and Whitten 1992; Monk et al. 1997; WWF-Indonesia n.d.). Logging has also grown in importance; for instance, Damar Island was densely forested until the late 1980s, when logging began on a large scale to supply timber to the outer arc islands, where the forests had already been more heavily exploited. As a result, fire-resistant Casuarina junghuhniana grows in pure stands in cleared areas, and Mt. Mutis, on West Timor, is covered almost exclusively by Eucalyptus urophylla (Monk et al. 1997). This problem is worsening as the human populations expand. Savanna areas are especially prone to erosion. This ecoregion is highly threatened. In previous centuries, many forest resources such as sandalwood were depleted through uncontrolled exploitation (Monk et al. 1997).
Justification of Ecoregion Delineation
The drier forests in Nusa Tenggara were placed in three ecoregions that corresponded to the biogeographic units identified in Monk et al (1997). These are Lesser Sundas Deciduous Forests [AA0201], which includes the chain of islands extending from Lombok, Sumbawa, Komodo, Flores, and the smaller satellite islands corresponding to the Flores biogeographic unit; Timor and Wetar Deciduous Forests [AA0204], corresponding to the Timor biogeographic unit; and the Sumba Deciduous Forests [AA0203], corresponding to the Sumba biogeographic unit. All three ecoregions belong to the tropical dry forests biome.
References for this ecoregion are currently consolidated in one document for the entire Indo-Pacific realm.
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.
For more general information on this ecoregion, go to the WildWorld version of this description.All text by World Wildlife Fund © 2001