Rajang Mangrove Forest
Location:
1°58'-2°27'N, 111°09'-111°32'E; the western part of the Rajang Delta, 40 km west of Sibu, Sixth Division, Sarawak.
Area:
125,000 ha; Rajang Mangrove Forest Reserve 87,544 ha.
Altitude:
Mostly near sea level, with hillocks rising to 90m.
Biogeographical Province:
4.25.12.
Wetland type:
06, 07 & 11.
Description of site:
A large area of mangrove forest in a complex deltaic system of channels and islands at the mouth of the Batang Rajang. Some fourteen subtypes of mangrove forest have been described for the area, including nipa swamp. Most parts of the forest are situated on raised ground created by the mound-building mud lobster. Rotational clear-felling for wood-chips has been practised since 1968 and has severely degraded a substantial area of the mangrove forest. The coast south of Kuala Rajang consists mainly of accreting mangrove and Casuarina on a sandy substrate. Between Kuala Rajang and Kuala Beiawai, the predominant vegetation is Casuarina, with accreting mangrove at Jerijeh Sands. North of Kuala Belawai, there are areas of eroding mangrove forest, Casuarina, agricultural land and some accreting mangrove on sandy or muddy substrate. The median tidal range at Rajang is 3.5m.
Climatic conditions:
Humid tropical climate with an average annual rainfall of 3,000 mm. The region is not directly exposed to the northeast monsoon. The peak monthly rainfall occurs in December and January.
Principal vegetation:
Extensive mangrove forests; Chai (1975) has recognized fourteen subtypes as follows:
1. Sonneratia alba
2. Avicennia alba and A. marina
3. Bruguiera parviflora with Xylocarpus granatum and Heritiera littoralis; Excoecaria agallocha, Oncosperma tigillarium and Myrsine umbellulata further inland.
4. Rhizophora apiculata
5. Rhizophora apiculata and Xylocarpus granatum
6. Bruguiera gymnorhiza
7. Bruguiera sexangula
8. Excoecaria agallocha
9. Nypa fruticans
10. Rhizophora apiculata and Bruguiera spp
11. Bruguiera spp, Rhizophora apiculata and Xylocarpus granatum.
12. Xylocarpus granatum, Bruguiera spp, Rhizophora apiculata and Excoecaria agallocha
13. Heritiera littoralis, Bruguiera sexangula and Excoecaria agallocha
14. Acrostjchum aureu
Land tenure:
Mainly state owned.
Conservation measures taken:
Some 87,544 ha are included within the Rajang Mangrove Forest Reserve.
Conservation measures proposed:
No information.
Land use:
Commercial and subsistence fishing, and commercial forestry (clear-felling of mangroves for the production of wood-chips). Traditional fishing activities include the use of gill nets, barrier nets, fishing stakes, beach seine nets, cast nets, crab traps and fish traps, and the collecting of molluscs and jelly-fish (Pang, 1985). The Sarawak Woodchip Company was first issued a licence in 1968, since when it has been operating using a 25-year rotation and annual coupe of about 600 ha (1,500 acres). However, regeneration is poor, with less than 10% successful regeneration in exploited areas. The Rajang is a major waterway for boat traffic, with the towns of Sibu and Sarikei both situated on the river bank.
Possible Changes in Land use:
No information.
Disturbances and threats:
The principal threat is over-exploitation of the forestry resources. Hatchlings of the Estuanine Crocodile Crocodylus porosus are caught for sale to commercial rearing pens in Sanikei and Sibu. There are unconfirmed reports of an illegal live trade in crocodiles to Singapore. River traffic and intensive fishing activities cause a considerable amount of disturbance to the crocodiles.
Economic and social values:
The mangroves maintain a fishery of great commercial importance both within the delta area and offshore. Pang (1985) has discussed the economics of the traditional fishing activities. It has been estimated that the value of the mangrove forest to the prawn fishery is far greater than the income derived from the wood-chip industry (Sarawak State Conservation Strategy). Some of the area is moderately suitable for agriculture but most of it has no agricultural potential whatsoever (Department of Agriculture, 1982b).
Fauna:
An important staging and wintering area for large numbers of migratory shorebirds and terns. During a waterfowl survey in September-November 1985, 330 shorebirds and 2,300 terns were recorded between Kuala Selalong and Kuala Rajang, and a further 750 shorebirds and 900 terns between Kuala Rajang and Kuala Belawai. Twenty-one species of shorebirds and six species of terns were present, the most abundant shorebirds being Tringa totanus, Xenus cinereus, Charadrjus leschenaultjj and Numenjus phaeopus, and the most abundant terns, Sterna albifrons and S. hirundo. The shorebirds included six Numenius madagascariensis (between Kuala Rajang and Kuala Belawai).
Mammals include the endangered Proboscis Monkey Nasalis larvatus, and reptiles include the Estuarine Crocodile Crocodylus porosus. The latter breeds near Sungei Mu, but is now rare, presumably because of the harvesting of hatchlings.
At least 43 species of fishes have been recorded, and four species of prawns are harvested on a commercial scale. Thalassina anomala occurs in great abundance.
Special floral values:
An extremely rich mangrove forest with many different forest subtypes; one of the most diversified mangrove forests in Sarawak.
Research and facilities:
Forest inventories were carried Out in 1951-54 and 1967 (Yong, 1967c), and the Department of Agriculture (1982b) has conducted a soil survey in the area. Other research has included a crocodile survey in 1985 (Cox & Gombek, 1985), several studies on the mangrove vegetation (e.g. Chai, 1975), a study of the Proboscis Monkeys (Salter & MacKenzie, 1981), a study of traditional fishing methods (Pang, 1985), and a coastal habitat and shorebird survey (Edwards et al., 1986).
References:
Cox & Gombek (1985); Chai (1974 & 1975); Chai & Lai (1980); Department of Agriculture (1982b); Edwards et al. (in prep); Pang (1985); Salter & Mackenzie (1981); WWF Malaysia & State Planning Unit of Sarawak (1985); Yong (1967c).
Criteria for Inclusion:
1b, 1e, 2a, 2c, 3b.
Source:
National Parks and Wildlife Office (Sarawak Forest Department), Sarawak Marine Fisheries Department and Asian Wetland Bureau.