Southeastern Asia: Islands of Java and Bali in Indonesia

The Eastern Java-Bali Rain Forests [IM0113] are found on one of the most actively volcanic islands in the world. Once the home of the extinct Javan and Balinese tigers (Panthera tigris sondaicus and Panthera tigris balica, respectively), these forests still contain one of the most endangered and high-profile songbirds in the world, the Bali starling (Leucopsar rothschildi). Almost all of this ecoregion's natural habitat was cleared long ago by logging interests and for agriculture and settlements to provide for a rapidly expanding, dense human population. Only tiny fragments of natural forests remain, and these are also disturbed.

  • Scientific Code
  • Ecoregion Category
  • Size
    20,800 square miles
  • Status
  • Habitats

Location and General Description
This ecoregion represents the lowland moist forests of eastern Java and Bali in the Indonesian Archipelago. Based on the Köppen climate zone system, this ecoregion falls in the tropical wet and dry climate zones (National Geographic Society 1999), although as one moves east on Java there is increasing seasonality of precipitation. Java probably did not exist before the Miocene (24 m.y. ago). Bali did not emerge until as recently as 3 million years ago. Truly born of fire, the islands of Java and Bali are the result of the subduction and remelting of the Australian-Indian Ocean tectonic plate beneath the Eurasian tectonic plate at the Java trench. The melted crust has risen as volcanoes and, along with subsequent sedimentation, created Java. Therefore, the surface geology consists of Tertiary and Quaternary volcanics, alluvial sediments, and areas of uplifted coral limestone. Twenty of the volcanoes on Java and Bali have been active in historic times, and they are among the most active volcanic islands in the world. During previous ice ages, when sea levels were much lower, Java and Bali were connected to Sumatra, Borneo, and the rest of the Asian mainland (Whitten et al. 1996).

The climate in eastern Java and Bali is drier than in the western part of Java; therefore, the lowland forests are predominantly moist deciduous forests, with semi-evergreen rain forest along the south coast and dry deciduous forest along the north coast. No one family dominates the forests of Java, as is the case with the dipterocarps in Sumatra and Borneo.

Java and Bali's deciduous forests generally are lightly closed, with few trees exceeding 25 m. Borassus and Corypha palms are good indicators of the seasonal climates that generate deciduous forests in the region. Moist deciduous forests have 1,500-4,000 mm of rainfall annually, with a four- to six-month dry season. Dry deciduous forests have less than 1,500 mm of annual rainfall and more than six dry months. Common lowland deciduous trees in eastern Java and Bali are Homalium tomentosum, Albizia lebbekoides, Acacia leucophloea, A. tomentosa, Bauhinia malabarica, Cassia fistula, Dillenia pentagyna, Tetrameles nudiflora, Ailanthus integrifolia, and Phyllanthus emblica. Many herbaceous plants are confined to the deciduous forests (Whitten et al. 1996).

Semi-evergreen rain forest is slightly more seasonal than the evergreen rain forest found in western Java, with two to four dry months each year. The most common species in the rain forests of Java are Artocarpus elasticus (Moraceae), Dysoxylum caulostachyum (Meliaceae), langsat Lansium domesticum (Meliaceae), and Planchonia valida (Lecythidaceae). Little forest remains below 500 m in Bali, so the natural forest composition is somewhat unclear, but trees commonly found in the remnants of Bali's lowland rain forests include Dipterocarpus hasseltii, Planchonia valida, Palaquium javense, Duabanga moluccana, Meliosma ferruginosa, Pterospermum javanicum, and Tabernaemontana (Whitten et al. 1996).

Limestone forests on Java and Bali have basal areas similar to those of other lowland forest types and apparently contain no plant endemics, but because they often grow on steep slopes of shallow soils, their growth pattern is affected. Limestone forests are found on Nusu Barung and Nusa Penida (Whitten et al. 1996).

Biodiversity Features
The overall richness and endemism for this ecoregion are low to moderate when compared with those of other ecoregions in Indo-Malaysia.

The ecoregion harbors 103 mammal species. The Kangean Islands, off the northern coast of Java, have uplifted limestone deposits with numerous caves that harbor fourteen of these islands' fifteen bat species (Whitten et al. 1996). Fruit bats play an exceptionally important ecological role by pollinating and dispersing plants. Of special significance is the cave fruit bat (Eonycteris spelaea), which is a pollinator of the economically important durian tree (Durio zibethinus) (Whitten et al. 1996). The endangered Bawean (or Kuhl's) deer (Axis kuhlii), confined to the small island of Bawea (MacKinnon and MacKinnon 1986), is a strict endemic of this ecoregion (table 1). The other endemic mammal is the vulnerable Javan warty pig (Sus verrucosus). Additional mammal species of conservation significance are the endangered Javan yellow-throated marten (Martes flavigula robinsoni) and banteng (Bos javanicus). The Javan subspecies of leopard on Java (Pantera pardus melas) is also considered endangered (IUCN 2000). Two tiger subspecies, the Javan and Balinese tigers (Panthera tigris sundaica and Panthera tigris balica, respectively), once inhabited these islands but are now extinct. The Balinese tiger disappeared by the end of World War II, but reports of Javan tigers persisted into the 1970s in the southeast (Nowell and Jackson 1996).

Table 1. Endemic and Near-Endemic Mammal Species.

  Family Species
Suidae Sus verrucosus
Cervidae Axis kuhlii*

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

This ecoregion harbors almost 350 bird species, including ten endemic and near-endemic species (table 2). This ecoregion overlaps partially with the Java and Bali forests and Javan coastal zone EBAs. Together these two EBAs contain thirty-seven restricted-range bird species, only some of which are found in the lowlands of this ecoregion. Included are the critically endangered Bali starling (Leucopsar rothschildi) and the endangered Javan hawk eagle (Spizaetus bartelsi) (Stattersfield et al. 1998).

Table 2. Endemic and Near-Endemic Bird Species.

  Family Common Name Species
Accipitridae Javan hawk-eagle Spizaetus bartelsi
Charadriidae Javan plover Charadrius javanicus
Charadriidae Sunda lapwing Vanellus macropterus
Cuculidae Sunda coucal Centropus nigrorufus
Strigidae Javan owlet Glaucidium castanopterum
Sturnidae Bali myna Leucopsar rothschildi*
Timaliidae White-breasted babbler Stachyris grammiceps
Timaliidae White-bibbed babbler Stachyris thoracica
Timaliidae Crescent-chested babbler Stachyris melanothorax
Timaliidae Grey-cheeked tit-babbler Macronous flavicollis

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

Current Status
Almost all of this ecoregion's natural habitat has long been cleared by logging interests and for agriculture and settlements to provide for a rapidly expanding, dense human population. Only tiny fragments of natural forests remain, but they are also disturbed to some degree. The largest remaining blocks of forest in this ecoregion are found at Lebakharjo and Bantur, along the coast south of Malang (Whitten et al. 1996). There are eighteen protected areas that cover 2,330 km2 (4 percent), although the majority are small (less than 100 km2) (table 3). The largest is Meru Betiri National Park, although the total size of Gunung Raung that extends into the ecoregion exceeds 1,000 km2.

Table 3. WCMC (1997) Protected Areas That Overlap with the Ecoregion.

  Protected Area Area (km2) IUCN Category
Bawean 190 IV
Gunung Celering 30 I
Gunung Butak 10 I
Bekutuk 20 I
Gunung Maria 160 ?
Pulau Saobi (Kangean Islands) 60 ?
Sumber Semen 30 ?
P. Sembu 10 I
Nusu Barung 80 I
Eko Boyo 20 ?
Teluk Lenggasana 130 ?
Gunung Ringgit 60 ?
Gunung Beser 60 ?
Bali Barat [IM0167] 310 II
Meru Betiri [IM0167] 430 II
Gunung Raung [IM0167] 100 ?
Baluran 250 II
Banyuwangi 380 IV
Total 2,330  

Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.

Types and Severity of Threats
Anthropogenic fires are common here, and centuries of burning have resulted in monospecific stands of fire-resistant species, usually Tectona grandis (FAO 1981). Most of the larger trees usually are felled by villagers (Whitten et al. 1996) or have succumbed to logging operations. Hunting is rife. The larger fruit bats, known as flying-foxes, are hunted extensively in Indonesia for food and medicine, but generally all fruit bats are killed by orchard owners who think they damage crops, even though these species play an important role in flower pollination and seed dispersal (Whitten et al. 1996). Shifting cultivation by large and rapidly expanding populations has led to extensive erosion (IUCN 1991).

Justification of Ecoregion Delineation
MacKinnon (1997) included the islands of Java and Bali in biounit 22 (with three subunits). Western Java is wetter than the eastern half of the island, and the forests are richer in species (Whitten et al. 1996; MacKinnon 1997). There are also floristic differences between the lowland and montane vegetation in Java and Bali (Whitmore 1984; Whitten et al. 1996). Therefore, using MacKinnon's subunit boundary, we delineated the Western Java Rain Forests [IM0168] to represent the moister evergreen forests to the west and the Eastern Java-Bali Rain Forests [IM0113] to represent the drier, less species-rich forests of eastern Java and in Bali. However, we also extracted the montane forests into distinct ecoregions-Western Java Montane Rain Forests [IM0167] and Borneo Montane Rain Forests [IM0103]-using the 1,000-m elevation contour of a DEM (USGS 1996).

References for this ecoregion are currently consolidated in one document for the entire Indo-Pacific realm.
Indo-Pacific Reference List

Prepared by: John Morrison
Reviewed by: