Pulau Bruit
Location:
2°21'-2°47'N, 111°17'-111°25'E; in the Rajang Delta, 150 km northeast of Kuching, Daro District, Sixth Division, Sarawak.
Area:
c.53,000 ha
Altitude:
0-1.5m.
Biogeographical Province:
4.25.12.
Wetland type:
02, 06, 07, 19 & 21.
Description of site:
A low-lying island in the delta of the Rajang River, with extensive intertidal mudflats and actively accreting mangroves at the northern end, and agricultural areas in the south. There is a small estuary at Tanjung Sink. The interior of the island consists of degraded peat swamp forest and rice fields with some areas of mature peat swamp forest. The peat swamps are of recent origin and have a maximum depth of 6.7m. They are dome-shaped and drain radially on the surface. Salinities in the coastal zone range from 18-34 p.p.t. The swamps in the interior of the island are flooded during the monsoon period (November-January), and are fresh to brackish. The site includes the highly productive coastal inshore waters up to a depth of 6m.
Climatic conditions:
Humid tropical climate with an average annual rainfall of less than 2,000 mm. The wettest months are April and October-December, the driest, January-February and July. The climate is generally equatorial, with rain from both the northeast and southwest monsoons, although the latter is mitigated by the mountains of Sumatra.
Principal vegetation:
Predominantly accreting mangrove forest dominated by Avicennia marina with an admixture of other species further inland. These include Bruguiera gymnorhiza, B. parviflora, Ceriops sagal, Rhizophora mucronata, Sonneratia alba, Hibiscus tiliaceus, Kandelia candel, lylocarpus granatum, S. ovata. Excoecaria agallocha, Acrostichum aureum and Acanthus ebracteatus. There is some peat swamp forest in the interior of the island. Other areas are mainly rice fields.
Land tenure:
The southern half of the island is state owned (Protected Forest) and the remainder is mainly state land, although there may be some private ownership in the interior of the island.
Conservation measures taken:
Partly included in the Pulau Bruit Protected Forest.
Conservation measures proposed:
It has been proposed that the intertidal area along the west coast of the island from Tanjung Sink to Kampong Bruit be declared a Wildlife Sanctuary (Edwards et al., 1986; Howes et al., 1986; Bennett, 1986). The National Parks and Wildlife Office of the Sarawak Forest Department is implementing gazettement of this sanctuary (the Tanjung Sink Wildlife Sanctuary). Howes et a!. (1986) have recommended that further research should include (a) studies on all aspects of the links between the mudflat/mangrove ecosystem, offshore fishing yields and the utilization of the mudflats and mangroves by migratory and resident waterfowl populations, and (b) agricultural feasibility studies prior to further development of rice fields in the northern sector of the island.
Land use:
Fishing and harvesting of mangrove products. The inshore waters are a major fishing ground for prawns and fin fish. Some hunting also occurs, mainly of Cervus unicolor. Much of the interior of the island is cultivated for rice and water melons.
Possible Changes in Land use:
The Department of Drainage and Irrigation has proposed that the northern part of Pulau Bruit, near Tanjung Sink, be drained and reclaimed for the cultivation of rice and coconuts. This scheme would affect some 9,000 ha, and would include 1,840 ha of Skim Pengaliran Tanjung Sink, Blocks A & C. The effect of the scheme on the mangroves at the north end of the island is uncertain. Restricting the flow of water would at best impede the accretion of the mangroves and at worst might kill them off (Bennett, 1986). I Also, it is very unlikely that the cultivation would be successful as most of the area comprises organic soils with severe limitations to agriculture (Department of Agriculture, 1982b).
Disturbances and threats:
Reclamation of a part of the island for cultivation is likely to affect the natural drainage and energy flow through the mangrove forest, and this could lead to decreased accretion or coastal erosion, with consequent devaluation of the area for wildlife and fisheries production.
Economic and social values:
The mangrove forest and mudflats are important in maintaining the offshore penaeid prawn fisheries. In 1983, 1,700 metric tonaes of prawns were landed from the adjacent waters (Bejie, 1983). The wetlands also support a locally important fishery, providing protein for the villages on the island. The island provides excellent opportunities for scientific research on accreting mangrove systems, zoo-benthic biomass in intertidal areas and shorebird utilization. Most of the area is highly unsuitable for agriculture.
Fauna:
The island is extremely important for herons and egrets, migratory shorebirds and terns. At least 500 herons and egrets of twelve species, 16,000 shorebirds of 25 species and 14,000 terns of seven species utilize the area at certain times. The island may be a regular wintering area for the rare Chinese Egret Egretta eulophotes; 16 were observed in November 1985 and five in April 1986. The mudflats are particularly important for the Asian Dowitcher Limnodromus semipalmatus and Far Eastern Curlew Numenius madagascariensir, over 5% of the known world population of the former and over 4% of the known world population of the latter have been recorded. Some 380 Garganey Anas querquedu!a were present in November 1985, an unusual concentration of this species in Borneo. The island may be a breeding area for the Lesser Adjutant Stork Leptoptilos javanicus.
Mammals known to occur include Macaca fascicularis, Sus barbatus, Lutra sumatrana, Cervus unicolor, Felis bengalensis -and Rastus exulans. The Silvered Langur Presbytis cristata, a species endangered in Sarawak as a whole, is common. All the residents of Kampung Tekajong interviewed by Bennett (1986) said that the Proboscis Monkey Nasalis larvatus occurs, and a few individuals were observed by P. Ngau (NPWO) in 1972 and Howes in 1986. Reptiles include the River Monitor Varanus salvator.
The waters around the island support a rich fish fauna, notably species of Clupeidae, Rajiformes, Scaenidae, Trachysunidae, Tnichiunidae, Carangidae, Chinocentridae and Stomateidae. Prawn species of commercial importance include Penaeus indicus, P. penicillatus, P. merguiensis. Metapenaeus brevicornis, M. lysianassa, M. aff is, M. joyneri, Parapeneopsis gracillima and P. hardwickii.
Special floral values:
The area contains an excellent example of accreting Avicennia marina forest, with typical Bruguiera mangrove forest on its landward side.
Research and facilities:
A forest inventory has been carried out and research plots have been established by the Forest Department. Annual fish and prawn surveys are conducted off the island as pant of a general survey of Sarawak waters, and some studies have been made on the wildlife, particularly the waterfowl.
References:
Anderson (1964); Bejie (undated); Bennett (1986); Cheong (1975); Department of Agriculture (1982b); DID Sanawak (1979/80); Edwards et al. (1986 & in prep); FAO (1974); Gambang (1986); Howes & NPWO (1986b); Scott (1969).
Criteria for Inclusion:
123.
Source:
Albert Chuan Gambang, John R. Howes and National Parks and Wildlife Office (Sarawak Forest Department).