(I) Physical CharacteristicsGunung Mulu is the largest national park in Sarawak (Jermy, 1982; SFD, 1982). The area comprises of gentle river valleys and floodplains in the northwest, rising to a line of steep, rugged limestone mountains and deep gorges running through the heart of the national park, incorporating peaks of Gunung Mulu (2,376 m asl), Gunung Benerat (1,600 m asl) and Gunung Api (1,692 m asl) and Gunung Buda (963 m asl) (SFD, 1982; Hazebroek and Abang Kashim bin Abang Morshidi, 2000). The national park also has one of the finest caves in the world (Smart, 1985; Brook et al., 1982). The entire south-eastern half of the national park is occupied by the Gunung Mulu massif, which is made up of shales and interbedded sandstones. Together with sedimentary rocks, they make up the Mulu Formation, estimated about 4,000-5,000 m thick and 40-90 million years old (Late Cretaceous to Late Eocene). Sandy soils have developed on the Mulu Formation rocks. The flanks of the mountain are dissected with steep valleys. The southern limestone hills are made up of the Melinau Limestone. The limestone landscapes are very rugged and are some of the world's best limestone weathering. In the north-western part of the area, overlying the Melinau Limestone, dark grey or blackish shales with minor sandstones form the Setap Shale Formation (Liechti et al., 1960). (II) Climatic ConditionsTemperature decreases with increasing altitude, from an average of 25oc around park hq (30 m asl) to an average of 16.3oC at 1,750 m asl. Annual rainfall is high with at least 5,000 mm throughout the park except at the summit of Gunung Mulu. Rain peaks in April-May and October-November, and the lowest in August-September. Rainfall increases then sharply decreases with altitude, rising from 5,078 mm at 65 m asl, to 6,802 mm at 1,700 m asl, then dropping sharply to 4,882 mm at the summit of Gunung Mulu (SFD, 1982).
Gunung Mulu National Park is one of the most important IBAs in Sarawak due to its rich bird diversity and vegetation type (Davison 1979; MacKinnon and Phillipps 1993) making it the best representative of the lowland and hill forest biome in Sarawak. Two hundred and sixty-two species have been recorded with 119 species (1 Endangered, 12 Vulnerable, 58 Near Threatened) restricted to the lowland forest and another nine to the montane forest. The national park is also known to contain large pheasants such as the Wattled Pheasant Lobiophasis bulweri and all eight hornbill species in Sarawak (Kemp and Kemp 1974). Other Near Threatened bird species found in the park include the Oriental Darter Anhinga melanogaster, Lesser Fish-eagle Ichthyophaga humilis and Bornean Frogmouth Batrachostomus poliolophus (Medway, 1980; Smythies, 1999). Twenty-four species are restricted to the Sundaic hill dipterocarp and montane forest EBA in Sarawak, of which three are Near Threatened.
Non-bird biodiversity: The national park boasts an incredible diversity of flora and fauna. Approximately 60 species of mammals (Hazebroek and Abang Kashim bin Abang Morshidi, 2000). 75 species of frogs and toads (Hazebroek and Abang Kashim bin Abang Morshidi, 2000).900 species of butterflies, 2,400 species of moths, 5,000 species of beetles and various others (Bright, 2000; Holloway, 1984a, 1984b).Incredible cave fauna including an enormous colony Wrinkle-lipped Bats (Tadarida plicata) estimated at between 600,000 to over 5 million. Their emergence from the structure at dusk is one of the most spectacular sights in the national park. Mossy-nest Swiftlets (Collocalia salagana) and Edible-nest Swiftlet (C. fuciphaga) roost and nest in the caves (Chapman, 1985).(I) Globally threatened mammals (IUCN, 2002): ENDANGERED: Orang-Utan Pongo pygmaeus; VULNERABLE: Pig-tailed Macaque Macaca nemestrina, Smooth-tailed Treeshrew Dendrogale melanura, Jentink's Squirrel Sundasciurus jentinki; NEAR THREATENED: Bornean Gibbon Hylobates muelleri, Long-tailed Macaque Macaca fascicularis, Grey Fruit Bat Aethalops alecto, Creagh's Horseshoe Bat Rhinolophus creaghi, Philippine Horseshoe Bat Rhinolophus philippinensis, Lesser Tailless Horseshoe Bat Coelops robinsoni; DATA DEFICIENT: Hose's Leaf-Monkey Presbytis hosei, Malayan Sun Bear Helarctos malayanus(II) Globally threatened reptiles (IUCN, 2002): No information.(III) Globally threatened plants (IUCN, 2002): CRITICAL: Parashorea macrophylla, Shorea platycarpa, S. seminis, S. acuta, Hopea nutans, Dipterocarpus lowii; ENDANGERED: Dryobalanops beccari, Shorea albida, S. obscura, S. argentifolia, S. maxwelliana, S. ovata, Hopea vaccinifolia, Cotylelobium burkii; VULNERABLE: Santiria nigricans, Scaevola muluensis, Nepenthes lowii, N. muluensis, N. bicalcarata, Microtropis rigida, Combretocarpus rotundatus, Eusideroxylon zwageri, Callophyllum havilandii; NEAR THREATENED: Myristica lowiana; LOWER RISK/conservation dependent: Elaeocarpus cordifolius; DATA DEFICIENT: Pentaspadon motleyi
Habitat and land use
All the major inland vegetation types of Borneo can be found here (Anderson and Chai, 1982; Proctor et al., 1982, 1983). The vegetation of the Park can be classified as lower mixed dipterocarp forest, lower montane forest, mossy/upper montane forest, summit zone vegetation, lowland riverine forest, kerangas forest and peat swamp forest.Lower mixed dipterocarp forest (including lowland limestone forest). Species found here include Dryobalanops beccarii, Durio spp., Garcinia spp., Mangifera spp., Syzygium spp., Diospyros spp., Licuala spp., Pinanga spp., Hopea andersonii, Shorea multiflora, Amorphophallus cf. lambii and Paphiopedilum sanderianum.Lower montane forest (including lower montane limestone forest). Quercus subsericea, Eugeissonia utilis, Hopea argentea, Parishia maingayi and Tristaniopsis obovata can be found in this habitat.Mossy/upper montane forest (including upper montane limestone forest). Trees from the families Fagaceae, Myrtaceae and Podocarpaceae dominate the montane forest. Pandanus spp. and Nepenthes stenophylla is also common on the limestone forest.Summit zone vegetation. Rhododendrons (Ericaceae) dominate the landscape. The recently described Nepenthes muluensis occurs only in the summit region. Another 26 species of trees and shrubs have been recorded in the summit.Lowland riverine forest. Common in the floodplain of the Sungai Melinau. Species found here include Eusideroxylon malagangai, Parashorea macrophylla, Calamus spp. and epiphytes.Kerangas forest. Occurs on terraces raised above the present floodplains of the rivers. Shorea albida is the dominant tree species in this habitat.Peat swamp forest. This habitat is restricted to a small area between Sungai Tarikan and Meladam. Principal dominant trees include Dryobalanops rappa, Shorea albida, S. platycarpa, Gluta spp. and Calophylllum spp. Inland mangrove species such as Combretocarpus rotundatus is also present.
Pressure/threats to key biodiversity
The expansion of resort tourism facilities may encourage mass tourism with higher impacts on fragile cave ecosystem, increased pollution and energy consumption and noise pollution.The park is increasingly surrounded by disturbed and degraded habitats, including logged forest and cultivation. This results in increasing isolation from genetic exchange of the flora and fauna within the park. Coupled with high habitat diversity within the park (meaning, for example, that total areas of protected peat swamp forest and kerangas forest are quite limited) this may raise questions about the long-term sustainability of those populations requiring large forest areas for survival (Davison, pers. comm.). Population densities of some large mammals and birds (primates and hornbills) are low, related to traditional hunting practices (Davison, pers. comm.). Over-harvesting of the birds' nest could potentially inflict long-term damage to the wild population (Stephen Then, 2001).
Gunung Mulu National Park was established in 1974 and protected under the National Parks and Nature Reserves (Amendment) Ordinance 1990. However, traditional rights of the local people are maintained where they are allowed to hunt pig, deer, fish and collect forest produce for food or handicraft in specified areas of the National Park. An extension of 35,000 ha (Limbang Division) has been proposed (SFD, 1982; Anderson et al., 1979). Gunung Mulu National Park is listed under Category II of the IUCN Protected Area Management Categories and more recently declared a UN World Heritage Site (Anon., 2002).