Indonesia: Island of Java

The Western Java Rain Forests [IM0168] are found on one of the most actively volcanic islands in the world. Once the home of the extinct Javan tiger (Panthera tigris sondaicus), these forests still contain one of the two remaining populations of one of the world's most threatened mammal species, the critically endangered Javan rhinoceros (Rhinoceros sondaicus). Unfortunately, only about 5 percent of the original habitat of this ecoregion remains.

  • Scientific Code
  • Ecoregion Category
  • Size
    16,100 square miles
  • Status
  • Habitats

Location and General Description
This ecoregion represents the lowland moist forests (less than 1,000 m) of western Java, Indonesia. Based on the Köppen climate zone system, this ecoregion falls in the tropical wet climate zone (National Geographic Society 1999), although as one moves eastward on Java there is increasing seasonality of precipitation. Java probably did not exist before the Miocene (24 m.y.). Truly born of fire, the island of Java is 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 was connected to Sumatra, Borneo, and the rest of the Asian mainland (Whitten et al. 1996).

The natural forests in the lowlands of western Java once included several forest subtypes, including extensive evergreen rain forest, semi-evergreen rain forest, moist deciduous forest along the northern coast, and dry deciduous forest, also along the northern coast of the island. The differences are mostly related to the seasonality of rainfall. There are also small areas of azonal limestone and freshwater swamp forests. No single tree family dominates the forests of Java, as is the case with the dipterocarps in Sumatra and Borneo (Whitten et al. 1996).

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). Semi-evergreen rain forest differs from evergreen rain forest by being slightly more seasonal, with two to four dry months each year (Whitten et al. 1996).

Java'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 to 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 found 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).

Limestone forests on Java 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 Mt. Cibodas, Nusu Barung, Padalarang, and Nusa Penida (Whitten et al. 1996).

Patches of freshwater swamp forest found throughout the ecoregion are relatively poor in species (Whitten et al. 1996). Rawa Danau, Banten in west Java is the largest remaining area of swamp forest in Java and Bali, and it contains many tree species now nearly extinct elsewhere in Java, such as Elaeocarpus macrocerus, Alstonia spathulata, wild mango (Mangifera gedebe), and Stemonurus secundiflora. Other rare plants include the sedge Machaerina rubiginosa, the aroid Cyrtosperma merkusii, and floating water plants such as Hydrocharis dubia and water chestnut (Trapa maximoviscii) (Whitten et al. 1996).

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

The ecoregion harbors 101 mammal species, including five endemics and near endemics (table 1). The larger of the two known populations of the critically endangered Javan rhinoceros (Rhinoceros sondaicus) is found in the extreme western part of the ecoregion, in Ujung Kulon National Park. The Javan gibbon (Hylobates moloch) is also critically endangered (IUCN 2000). Other species of conservation significance include the globally threatened surili (or Java) leaf monkey (Presbytis comata), fishing cat (Felis viverrina), wild dog (Cuon alpinus), Javan warty pig (Sus verrucosus), banteng (Bos javanicus), and slow loris (Nycticebus coucang) (MacKinnon and MacKinnon 1986; Whitten et al. 1996; IUCN 2000). The Javan subspecies of the yellow-throated marten (Martes flavigula robinsoni) and leopard on Java (Pantera pardus melas) are also considered endangered (IUCN 2000).

Table 1. Endemic and Near-Endemic Mammal Species.

Family Species
Rhinolophidae Rhinolophus canuti
Molossidae Otomops formosus
Hylobatidae Hylobates moloch
Suidae Sus verrucosus
Muridae Sundamys maxi

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

More than 350 bird species are known to occur in the ecoregion, including 9 endemics and near endemics (table 2). This ecoregion overlaps with two EBAs (Stattersfield et al. 1998): Java and Bali forests and Javan coastal zone. These two EBAs contain a total of thirty-seven restricted-range birds, including the extinct Javanese lapwing (Vanellus macropterus). Nine of these restricted-range birds are found in this ecoregion of lowland west Java (including the extinct lapwing) (Stattersfield et al. 1998; MacKinnon and Phillipps 1993).

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
Zosteropidae Javan white-eye Zosterops flavus
Timaliidae White-breasted babbler Stachyris grammiceps
Timaliidae White-bibbed babbler Stachyris thoracica
Timaliidae Grey-cheeked tit-babbler Macronous flavicollis
Timaliidae Crescent-chested babbler Stachyris melanothorax

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

The forests of west Java are more species-rich for plants than the rest of the island, with more than 3,800 species, including two endemic genera (MacKinnon and MacKinnon 1986; Whitten et al. 1996). These forests harbor two species of the giant insectivorous Rafflesia (R. rochussenii and R. patma) (Whitten et al. 1996).

Current Status
Only about 5 percent of the original habitat of this ecoregion remains. There are thirty-three protected areas that cover 3,045 km2 (7 percent), but most of the protected areas (twenty-eight) are small (less than 100 km2) (table 3). The largest, Ujung Kulon National Park, is significant for its Javan rhinoceros population.

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

Protected Area Area (km2) IUCN Category
Pulau Sangiang 20 DE
Gunung Tukung Gede 50 I
Muara Angke 30 I
Rawa Danau 70 I
Carita 30 V
Yanlapa 10 I
Depok 20 I
Tanjung Pasir 20 ?
Mawuk 20 ?
Gunung Karang 50 ?
Jayabaya 40 ?
Muara Gembong 30 ?
Muara Bobos 90 ?
Tanjung Sedari 90 ?
Muara Cimanuk 80 ?
Ujung Kulon 1,120 II
Cikepuh 140 IV
Peson Subah I, II 10 I
Ulolanang Kecubung 30 I
Unnamed 40 ?
Gunung Unggaran 70 ?
Ciogong 40 ?
Salatri 30 ?
Bojong Larang Jayanti 20 I
Gunung Selok 30 V
Leuwang Sancang 110 I
Pasir Salam 70 ?
Nusakambangan 200 ?
Gunung Kendeng 30 ?
Cikencreng 30 ?
Telaga Bodas 5 ?
Telogo Ranjeng 20 I
Gunung Pangasaman [IM0113] 400 ?
Total 3,045  

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

Java is one of the most densely populated islands in the world, so it is not surprising that very little natural habitat remains here (MacKinnon and MacKinnon 1986). Anthropogenic fires are common, and over the centuries burning has resulted in monospecific stands of fire-resistant species, usually Tectona grandis (FAO 1981). In many annual cropping systems, soils are left exposed during critical periods, resulting in extensive erosion (IUCN 1991). Illegal farming and felling even within protected areas are widespread, and an important timber tree Altingia excelsa has been nearly eliminated from the lowland forests (Whitten et al. 1996). In freshwater swamp forests, the exotic Mimosa pigra has the potential to become a very serious pest because it is fire-resistant and capable of forming impenetrable thickets (Whitten et al. 1996). Plans to construct a dam at the outlet of the Cidanau will destroy Rawa Danau, the only remaining extensive area of freshwater swamp in Java (Whitten et al. 1996).

Types and Severity of Threats
The threats that have degraded or destroyed most of this ecoregion in the past still threaten the remaining forest fragments. Political instability will continue to contribute to rampant destruction of these forests as existing environmental laws are routinely ignored and not implemented.

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 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: