Trusan-Sundar Mangroves
Location:
4°53'-4°58'N, 115°09'-115°19'E; stretching from Sungei Bangau in the west to Sungei Siang Siang in the east, near Sundar, Lawas District, Fifth Division, Sarawak. On the border with Brunei Darussalam.
Area:
c.20,300 ha.
Altitude:
Sea level.
Biogeographical Province:
No information.
Wetland type:
02, 06, 07 & 21.
Description of site:
An accreting deltaic mangrove system with extensive intertidal mudfiats and sand flats, and some freshwater swamp forest on the landward edge. The area is dominated by one main river, the Sungei Trusan, which supplies a heavy silt load for mud and sand flat deposition. The majority of the area is contained within Kenalian, Bumbun and Terentang Forest Reserves, where logging has been extremely intensive. Areas of up to one hectare or more have been virtually clear-felled. Only the area between Sungei Sepatai and Sungei Awat Awat is relatively untouched with a more or less intact canopy. Salinities range from 18.4 p.p.t. at Kampong Sinempuan to 0.92 p.p.t. at Sundar Besar, and less than 0.38 p.p.t. upstream from Kampong Aru. The median tidal range at Punang is 1.4m.
Climatic conditions:
Humid tropical climate with an average rainfall of 3,500-4,500 mm. The rainfall is more or less evenly distributed throughout the year, although there is a slight peak during the monsoon from September to January (400 mm per month).
Principal vegetation:
Mainly mangrove forest dominated by Rhizophora apiculata; also, areas inland where Nypa fruticans, Bruguiera gymnorhiza and Lumnitzera coccinea occur. Areas cleared of Rhizophora become infested with the fern Acrostichum aureum, and the eroding seaward edge is colonized by Casuarina equisetifolia. Fig trees Ficus spp are abundant along the Sungei Awat Awat. Heavily logged freshwater swamp forest occurs inland from the site.
Land tenure:
State owned (Sarawak State Government).
Conservation measures taken:
The mangroves are included within the Kenalian, Bumbun and Terentang Forest Reserves.
Conservation measures proposed:
Howes and NPWO (1986) proposed the creation of a Wildlife Sanctuary and the management of mangrove production forest. These proposals are in line with the concept of an International Coastal Resource Conservation Area within Brunei Bay which would include this site, site 28 and adjacent areas in Brunei Darussalam. Salter and MacKenzie (1981) proposed that undisturbed mangrove forest between Kuala Bangau and Kuala Trusan be made into a Wildlife Sanctuary for Proboscis Monkeys Nasalis larvatus. Bennett (1986) stressed the need for protection of the relatively undisturbed areas.
Land use:
Large-scale production forest (mangrove) for producing cord-wood for export to Taiwan. The area also supports a local fish-smoking industry and small-scale fishing for domestic consumption, and there is some hunting of Cervus unicolor and Sus scrofa. There are several settlements and patches of cultivation in the surrounding areas.
Possible Changes in Land use:
No information.
Disturbances and threats:
The clear-felling of mangrove forest continues on a large scale, and no efforts are being made to manage the resource on a sustainable yield basis. Illegal logging also takes place.
Economic and social values:
The mangrove swamps and intertidal mudflats are of great importance in maintaining the neighbouring inshore fishery. In 1973, the harvest of penaid prawns from the adjacent sea was valued at M$3 million. The mangroves are also an important source of fuel for a local fish-smoking industry. The soils are highly susceptible to the acid sulphate condition after clear-felling, and although some of the area is moderately suitable for agriculture, most of it has too severe limitations to be of any agricultural value (Department of Agriculture, 1982c).
Fauna:
Over 100 species of fishes have been recorded in the associated waters. The mudflats are of considerable importance for migratory shorebirds; seventeen species are known to occur, and up to 1,000 birds have been recorded at one time (e.g. in May 1986). The commonest species are Charadrius leschenaultii. Tringa totanus and Xenus cinereus. Other waterfowl include the rare Chinese Egret Egretta eulophotes and six species of terns, the commonest being Chlidonias hybrida and C. leucoptera. Mammals include the endangered Proboscis Monkey, Silvered Langur, Long-tailed Macaque and Irrawaddy Dolphin (Nasalis larvatus, Presbytis cristata, Macaca fascicularis and Orcaella brevirostris). Reptiles include the Estuarine Crocodile Crocodylus porosus and River Monitor Varanus salvator.
Special floral values:
The site constitutes a good example of Rhizophora forest, with Avicennia and Sonneratia forests to the seaward side and mixed Rhizophora and Bruguiera forest to the landward side.
Research and facilities:
Forest inventories were carried out in 1961, 1964 and 1978 (Ngui, 1978), and a soil survey has been undertaken (Department of Agriculture, 1982c). The Proboscis Monkeys have been investigated by Salter and Mackenzie (1981) and Bennett (1986), and Howes and NPWO conducted some shorebird research in May 1986.
References:
Bennett (1986); Department of Agriculture (1982c); Howes & NPWO (1986a); Ngui (1978); Salter & Mackenzie (1981).
Criteria for Inclusion:
1b, 1e, 2a, 2c, 3b.
Source:
John R. Howes, National Parks and Wildlife Office (Sarawak Forest Department) and E.L. Bennett.