Danau Sentarum
Location:
0°45'-1°02'N, 111°57'-112°20'E; north of the Kapuas River, 700 km upstream from Pontianak, West Kalimantan.
Area:
80,000 ha.
Altitude:
35m.
Biogeographical Province:
4.25.12.
Wetland type:
14 & 21.
Description of site:
A low-lying plain with some 40,000 ha of lakes and almost 40,000 of freshwater swamp forest and peat swamp forest, in the upper Kapuas river basin, some 700 km upstream from the delta. The plain is surrounded by hills rising to 400-500m, and a few isolated hills occur within the plain. This region, with its numerous lakes of various sizes and many interconnecting water courses, acts as a buffer for flood waters from the Kapuas River during the wet season, and regulates the flow of water further downstream. The lakes are shallow and ephemeral, and are best seen as extensive flood plains bearing a close similarity to the Grande Lac system in Kampuchea. The maximum depth of water during the wet season is about 7-8m. In most dry seasons, the lakes dry out completely leaving only a series of small streams. The pH is 5.0 in the lakes, 5.5-6.0 near the Kapuas River and about 4.0 in the peat swamps. The lake waters are coloured dark brown by tannic acids.
Climatic conditions:
Humid tropical climate with an average annual rainfall of about 4,500 mm. The wettest months are October, November, December, March and often April; the driest months, June, July and August. The maximum temperatures are 35.0-35.5°C; the minimum, 2 1.5-22.0°C.
Principal vegetation:
The aquatic vegetation includes Eichhornia crassipes, Polygonum spp, Cyperaceae and Poaceae. Stunted swamp forest is dominated by Barringtonia acutangula, Crown spp, Eugenia spp, Garcinia spp and Ixora mentangis. There are two types of freshwater swamp forest: forest near the Kapuas River is dominated by species of Calophyllum, Eugenia. Garcinia, Dyospyros and Melanorrhoea; elsewhere the swamp forest is characterized by Fragraea fragrans, Mallotus spp and Shorea balangeran. The peat swamp forest is dominated by Calophyliwn spp, Dryobalanops abnormis, Eugenia spp and Shorea seminis. Plant communities in adjacent areas include heath forest, hill dipterocarp forest and secondary forest.
Land tenure:
State owned (PHPA).
Conservation measures taken:
The area was declared a Wildlife Reserve (Suaka Margasatwa) in 1982. This conservation status is considered to be adequate, but actual protection is lacking
(Giesen, 1987).
Conservation measures proposed:
Giesen (1987) has made the following recommendation
1. that logging and shifting cultivation be prohibited within the primary forest areas;
2. that various restrictions be placed on fishing activities, including curbs on mechanization and the prohibition of fine-meshed nets;
3. that village growth be curtailed;
4. that the boundary of the reserve be realigned to follow natural boundaries such as rivers
Land use:
Fishing, shifting cultivation, cultivation of rice and hunting. About 2,800-3,500 1 people live in some twenty villages within the reserve. Most are dependent on fisheries for
their livelihood, while cultivation, logging and trade are of marginal importance.
Possible Changes in Land use:
Large tracts of the surrounding forests have been granted in concession to logging companies. There are plans to construct six dams for irrigation purposes and electricity generation on tributaries of the upper Kapuas River. These will have a profound effect on the water regime of the Sentarum lakes and floodplain, and may result in a decline in fisheries production.
Disturbances and threats:
Illegal logging, heavy hunting pressure and considerable human disturbance from the many small villages in the area. The forests are very susceptible to fire, and many hundreds of hectares have been lost to forest fires in recent years. Less than 1% of ~ the reserve has been affected by shifting cultivation, but 50-70% of the adjacent hill slopes have been cleared of their original vegetation. The population of Asian Arowana Scieropages 1 formosus is declining rapidly because of excessive trapping for the ornamental fish trade. Although the Arowana has been listed on Appendix I of CITES since 1975, international trade in the species continues.
Economic and social values:
At least 3,000 to 4,000 fishermen are active in the lakes within the reserve. The annual production of fishes in the reserve is estimated at 3,000 metric tonnes. Productivity is high compared to other floodplain fisheries: 37.5 kg/ha/year for combined lakes and inundated forests, and 75 kg/ha/year for lakes alone. The total value of the fisheries in 1985 was calculated to be over 15,000 million rupees for edible fish and 775 million rupees for ornamental fish (Giesen, 1987). Some 300 tonnes of fish are consumed locally; the remainder is dried and salted for sale.
Of 207 plant species investigated by Giesen (1987), no fewer than 87% have a known use in the area, and most of these are useful to man.
Fauna:
Some 113 species of fishes have been recorded. The commonest genera are:
Puntius (7 species) Kryptopterus (6 species)
Osteochilus (6 species) Ophiocephalus (5 species)
Rasbora (5 species)
The most abundant species in the fish catches are Helostoma temmincki, Mystus nemurus, Cyclocheilichthys janthochin, Osteochilus melanopleura and Kryptopterus micronema. There is a marked seasonal migration of fish to and from the Kapuas River, and an annual cycle in the relative abundance of herbaceous and predatory fishes. The popular and very expensive red variety of the Asian Arowana Scieropages formosus occurs in the lake. Individuals of this variety, which in Indonesia is known only from West Kalimantan, may sell for as much as US$2,700 in Jakarta.
The lakes and swamp forests support a wide variety of waterbirds including Anhinga melanogaster, Ixobrychus cinnamomeus, Ardeola bacchus, Egretta spp, Ardea purpurea, Ciconia (episcopus) stormi, Sterna albifrons, the raptors Haliastur indus, Ichthyophaga ichthyaetus, 1. nana, the fish-owl Ketupa ketupu and the kingfisher Pelargopsis capensis.
Mammals known to occur in the swamp forests include Amblonyx cinerea, Nannosciurus melanotus, Nasalis larvazus, Macaca fascicularis, Cervus unicolor, Hystrix brachyura, Sus barbatus and Tragulus spp. Other species occurring in surrounding hill forests include Arctogalidia trivirgata, Helarctos malayanus, Hylobatus muelleri and Pongo pygmaeus.
Frogs are common. Common reptiles include Chitra indica, a tortoise, probably Testudo emys, Varanus borneensis and V. salvator. The Estuarine Crocodile Crocodylus porosus and False Gharial Tomistoma schlegelii still occur in the swamps, but are now uncommon.
Four species of molluscs have been recorded, including two species of freshwater mussels.
Special floral values:
Giesen (1987) recorded 282 species of plants of 70 families, including the first Bornean record of Gluta pubescens (Anacardinaceae) and a possible new species of Vazica (a dipterocarp). The latter is one of the commoner tree species in the inundated forests.
Research and facilities:
The area has been visited by few scientists. The main expeditions to date have been those of Molengraaff, a geologist, in 1900, Polak, a soil scientist, in 1949, Vans, an ichthyologist, in 1952, and Giesen, an ecologist, in 1984.
References:
Giesen (1987).
Criteria for Inclusion:
1b, 1e, 2a, 2b, 3b.
Source:
Marcel J. Silvius and Eva T. Berczy.