A river journey throughGunung Leuser National

Park, SumatraMichael P. Ghiglieri

The Gunung Leuser National Park, establishedby the Indonesian Government in 1980, coversmore than 7900 sq km of forests, ranging fromtropical lowland to subalpine. It protects manyendangered and threatened species. InOctober 1984 the author, acting as a biologistand guide on an exploratory rafting expedition,floated along the Alas River, which runsthrough the Park. He describes his journey andthe primates he recorded along the way.

The Gunung Leuser National Park, an amalga-mation of seven reserves in northern Sumatra,was legally established on 6 March 1980. Thisconservation triumph followed a decade of effortby the Nature Conservation and Wildlife Man-agement Service (PPA, now PHPA) of Indonesiaand the World Wildlife Fund. The Park's approx-imately 7900 sq km is divided into four altitudinalzones: tropical lowland (below 600 m, 12 percent), upland (600-1500 m, 48 per cent),mountainous (1500-2500 m, 35 percent), andsubalpine (above 2500 m, 5 per cent) (VanStrien, 1978). More than half the species ofmammals found in Sumatra occur there, includ-ing populations of endangered and threatenedlarge mammals now extinct over most of theirformer ranges in the Malay Archipelago and therest of South East Asia. For example, GunungLeuser still contains viable populations ofSumatran rhinoceros,* elephant, tiger, cloudedleopard, wild dog, Malayan sun bear, orang-utan,siamang, serow and other species (see alsoMartin, 1983; Blouch, 1984).

Indonesia contains one-tenth of the world's

*Scientific names of animals are given in Table 1.

104

tropical forest (Caufield, 1984), but deforestationis rapidly accelerating (Frey, 1978; Myers, 1984)and patchy remnants of primary forest areincreasingly more common than large blocks. Inview of this, Gunung Leuser is probably the mostimportant conservation area in South East Asia.

In October 1984, I was a biologist and guide onan exploratory Whitewater expedition organizedby SOBER Expeditions Inc. (Angels Camp, Cali-fornia) down the Alas River, which bisectsGunung Leuser National Park. We travelled byinflatable river boat from Agusan, the uppermostpoint on the Alas accessible within a half-hour'swalk from the road (and with adequate flow for aboat), to the southernmost boundaries of thePark, then beyond to the Indian Ocean. Duringriver travel, I recorded all my sightings of largemammals and orang-utan nests within theriparian corridor. In addition, by means of a low-altitude reconnaissance provided by a Mobil Oilhelicopter, we flew from the Ketambe ResearchStation founded by Herman Rijksen (1978) in1971, upstream along the Alas to its source on(Mount) Gunung Leuser, and to the summit. Thisallowed a quick evaluation of the physical con-dition of the north-west corner of the Park. Theentire 322-km river journey combined withapproximately 100 km (each direction) by air,with 51 km of air and river travel overlapping,provided a unique opportunity to examine thePark between its most distant boundaries.

The Alas River and its riverine habitats are dividedinto contrasting sections, both naturally by geo-graphic features and artificially by roads (Figure 1,Table 2). Section 1, its headwaters on Gunung

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Pristine, primary tropical forest cloaking the steep slopes ofAlas River canyon in Section 1. upstream from and isolatedfrom Agusan (M.P. Ghiglieri).

Leuser, extends approximately 50 km to thevillage of Agusan (elevation 950 m) and is access-ible only by foot (or helicopter . . .) along verysteep terrain. The rain forest is subalpine andmountainous, with a discontinuous upper canopystudded with emergents at lower elevations, and

Table 1. Scientific names of animals mentioned in the text

Clouded leopardCrab-eating macaqueElephantGibbonLeaf monkeyMalayan sun bearOrang-utanPig-tailed macaqueSerowSiamangSumatran rhinocerosTigerWild dog

Neofelis nebulosaMacaca fascicularisElephas maximusHylobates larPresbytis thomasiHelarctos malayanusPongo pygmaeusMacaca nemestrinaCapricornis sumatrensisHylobates syndactylusDicerorhinus sumatrensisPantkera tigrisCuon alpinus

shows no sign of unnatural disturbance. Huntingmay occur, but we saw no evidence of it.

Section 2, extending 51 km from Agusan to theKetambe Research Station, is mostly steep gorge,but contains 6-10 km of relatively level riversideland, where there are official non-Park enclavesof human settlement. Within the last five years,the narrow track that runs roughly parallel withthe Alas, connecting Kutacane with Agusan, hasbeen paved with tarmac. This has made com-munication and the marketing of local agriculturalproduce and natural products of the region mucheasier, which in turn makes settlement along theroad more attractive. There are several villagesalong the road, and in many places, where thetopography permits, the Gayo people have cutsmall swidden fields of 1 -10 ha along the river.

Despite this, the riverine rain forest upstream ofKetambe is still pristine, with limited evidence ofvegetative disturbance. Even after 10 cm of rainin October, the Alas here ran clear. Primates,

River journey through Gunung Leuser NP

Aerial view of non-park enclave near tarmac road in Section 2(M.P. Ghiglieri).

105

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especially crab-eating macaques, leaf monkeys,gibbons and siamang seemed common relative tohabitats outside the Park. I saw no orang-utans,but their nests were common locally.

Section 3, extending 60 km from Ketambe toMuara Setulen, is another elongated enclave onnon-Park land (the initial 8 km or so of this stretchis within the Park). This region is known as theAlas Valley and is populated by thousands ofAceh Alas people, primarily Muslim, plus morerecent immigrants of Christian Karo Batak. Asone travels downstream from Ketambe, thevalley widens and flattens and there is more andmore agricultural land. From Kutacane to MuaraSetulan, the valley is virtually one patchwork farmdotted with semi-natural plots. Near the river hereI saw no non-human primates.

The hills 1-2 km west of the Alas have beeneither clear cut, partially felled, or otherwise dis-turbed. Here, near the confluence with theMamas River, the Alas became increasingly

turbid with silt, presumably from agricultural run-off. To the east beyond Kutacane, the Alas Valleyhas long been inhabited by people.

Section 4, the Lower Gorge, begins about 2—3km downstream of Muara Setulen and extends32.5 km to the confluence with the Renun River.The west side of the Alas is in Gunung Leuser.Here the river has carved a course between twomountain ranges (approximately 2000-2500 melevation). Upstream of the Renun the habitat ofthe Lower Gorge is pristine rain forest. In order ofnumbers of sightings, long-tailed macaques,langurs, siamang, lar gibbon and orang-utans andtheir nests again appeared common.

The river is regularly fished using gill nets. In theforest I found a series of brush fences punctuatedwith eight polypropylene snares set apparentlyfor argus pheasant. The lower 100-400 m of thecanyon is extremely steep and offers only smallfishing camps under rock overhangs. Perhaps

ACEH

J Gunung Leuser NP

0 50 100 150I I I I

GAY0 HIGHLANDS/

RIAU

Figure 1. TheGunungLeuserNP, North Sumatra. This map is taken from Rijksen (1978).106 OryxVol 20 No 2, April 1986

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because of the steepness, the forest is virtuallyundisturbed and magnificent.

Section 5, the final 11 km of the Lower Gorge, liesbetween the confluences of the Alas with theRenun [here only a few kilometres west of JohnMacKinnon's (1974) study site for orang-utan]and with the Bengkong downstream. The Beng-kong forms the south-west boundary of GunungLeuser; the Renun side is unlogged timber con-cession. Here again, only the west side of the Alasis in the Park. Towards the end of the LowerGorge, the east side showed increasing signs ofexploitation and slash-and-burn agriculture.Poaching of individual trees on both sidesbecame more pronounced. Approximately 5 kmdownstream of the Renun confluence a bulldozerwas grading a timber extraction road from theeast. The operator told me it had taken him 8months to build the 30 km of road, then nearlyready for use. In this riparian corridor my sightings

Right: Recently cleared riparian forest adjacent to Alas River inSection 2 in preparation for swidden farming (M.P. Ghiglieri).

Table 2. Ecological characterization of the Alas River, from Gunung Leuser National Park to the Indian Ocean, Sumatra

Section

1.

2.

3.

4.

5.

6.

7.

End-points

Gunung Leuser toAgusan

Agusan toKetambe ResearchStation

Ketambe toMuara Setulen

Muara Setulen toRenun River

Renun River toBengkong River

Bengkong River toGelombang

Gelombang toIndian Ocean

Lengthin km*

50

51

60

32.5

11

58

110

Portionin park

100%

90%

10%

45%

50%

None

None

Navigability

Nil

Class VI, teamof experts only,portages

Class III toKutacane, thendugout canoe

Dugout canoe

Dugout canoe

Motor launch

Motor launch

Topography

Very steepgorge

Mostly steepgorge

Low gorge,majority isalluvial openvalley

Steep gorge

Low gorge

Low hills,open alluvialvalley

Ratalluvialvalley

Riverinehabitat type

Pristinerain forest

Rain forest

Agriculturemostly, someforest

Rain forest

Rain forest

Agriculture,rain-forestremnants,secondary

Agriculture,some secondgrowth forest

Influenceof humans

Nil

Minor

Complete

Minor

West, minorEast, substantialand increasing

Impacted,largestmammals notpresent

Complete

SubjectiveImpressionof wildlifestatus

Undisturbed(?)

Apparentlyundisturbed

Impacted tononeremaining

Lightlyimpacted

Impacted

Impacted

Almostnoneremaining

Information from US Army Map Service (Corps of Engineers) maps, Edition 1-AMS, Series T-503, Sheets NA 47-1, 2, 5, and 6 (1954).

River journey through Gunung Leuser NP 107

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of primates (with the exception of orang-utans,which I did not see, and their nests, which wererelatively rare) appeared only slightly reducedbelow those of Section 4.

Section 6 consists of 58 km of the Alas from theBengkong confluence to Gelombang. Lowrounded hills attenuate to nearly flat topography.Human habitation predominates and the level ofhuman modification to the riverine habitatincreases with proximity to Gelombang. How-ever, even in this section, on steep slopes withuncut blocks of rain forest I saw long-tailedmacaques, pig-tailed macaques, langurs,siamang, and lar gibbons. But these 'island'habitats became ever more scarce as we travelleddownstream.

Section 7, 110 km from Gelombang to the IndianOcean, is ecologically almost an extension ofSection 6. The main differences are that thetopography is level and the influence of humanscomplete. During our round-the-clock combineddescent and return to Gelombang, I saw only onegroup of langurs and one of long-tailedmacaques, both in patches of secondary forest.Many people in Gelombang, however, ownjuvenile or adolescent long-tailed macaques,which can be purchased for US$10.

Current laws regulating use of the Park by thepeople around it allow for continued access tosome of its natural products under the 'adat'system. Adat refers simply to traditional culturalpractices restricting the harvesting of forestproduce. In short, people can still enter the Parkto collect plants for medicinal or other personalneeds, but not for commercial exploitation. Intheory, the adat system is harmonious with theperpetuation of an ecosystem in a state close tothat of nature. Rijksen (1978) points out thatsome adat restrictions 'appear to aim at con-serving the delicate ecological balance in theclan's territory', but admits that this balance ispreserved only if the population governed byadat is itself kept in balance by ecological andcultural factors. Because of the impact of newlyimported ideologies, this is no longer the case.Over much of Sumatra, Rijksen warns, slash-and-burn agriculture stripped of adat restrictions ishighly destructive.108

A long-tailed macaque, the most common primate of theriparian habitat of the Alas River (M.P. Ghiglieri).

The adat system is easily abused by extending itto commercial exploitation. Van Strien (1978)noted the local disappearance of commercialspecies of rattan in Gunung Leuser through over-harvesting, for instance, and the local depletion ofmany dipterocarp species through the collectingof aromatic gums for the market by bark-girdlingtechniques, which kill the trees.

Other conflicts of interest exist between the goalsof the Park and the needs of people livingadjacent to it or within it. According to the Head ofthe Park, Mr Nasori S. Djajalaksana (pers.comm.), between 1979 and 1984, 19 peoplewere killed by tigers in or near the Park in forestand peripheral villages. Stock losses were morefrequent. During the same period, an average oftwo tigers per year were killed by poison bait ortrapped by the park staff using live bait for transferto zoos. In addition, elephants have occasionallydestroyed crops, necessitating compensationpayments (see also Caufield, 1984).

One solution is to move people out of the Parkand/or to centralize those living on its periphery.

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Public education is vital for such moves tosucceed, but even with it they are traumatic. Theexpensive failure of the Uning Puni relocationproject sponsored by the World Wildlife Fundillustrates this difficulty. Hundreds of forest Gayoliving in the Park and engaged in slash-and-bumfarming were relocated to a new village along theAlas in Section 2. The standard allocation for suchtranslocations is to provide each family with 2-25ha for growing commercial crops plus another 1 -5ha for their subsistence garden (see Caufield,1984). Within two years, the relocated Gayoabandoned Uning Puni and returned to theforest. Van Strien (1978) stressed the necessity togo beyond policing and public education bypromoting land reforms, intensifying existingagriculture, and promoting family planning.However, public education of local people doesremain a major need in the management ofGunung Leuser. Some local people reportedlybelieve it is a national park because the land hasbeen bound as a lien for debts incurred by

Below: Abandoned relocation project at Uning Puni inSection 2 of the Alas River in non-park enclave (M.P.Ghiglieri).

Above: Abandoned swidden plot 1 km upstream from theLower Gorge (Section 4) near boundary of Gunung LeuserNational Park (M.P. Ghiglieri).

River journey through Gunung Leuser NP

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Indonesia to The Netherlands (J. DeRuiter, pers.comm. at Ketambe). This explains for them theotherwise difficult to understand interest of Dutchresearchers at the Ketambe Research Station.

While expatriate researchers sometimes makegood watchdogs against incursions into the Park,and often train their Indonesian counterparts todo the same, neither fundamentally alters localpeoples' opinions about their own rights.Degradation of habitat due to incursions is aserious risk, one which threatens the geneticviability of populations of large mammals in thePark, for example orang-utans (Rijksen, 1982). Ingeneral, the growth of human populationsaround enclaves of great ape habitat seriouslythreatens the apes (Frey, 1978; Ghiglieri, 1984a,b). Mitchell (1984) recommended more surveysto categorize the distribution and abundance ofhabitat types and rare species in Gunung Leuser,plus more support for Indonesian graduatestudents in forest ecology to conduct research onthe effects of human-caused perturbations onhabitats, and more assistance to national parkstaff to revive the public relations programme ofthe 1970s.

Along with public education, increased tourismshould be promoted so that the Park may notonly begin to pay for itself, but also pay some ofthe people living around it (Ghiglieri, 1984b).Although the orang-utan rehabilitation centre atBohorok on the eastern side of the Park nearMedan receives many local tourists and functionsas an important centre for public education(Aveling and Mitchell, 1982), tourism in the AlasValley is barely in its infancy. The potential forincreasing it is great. Whitewater rafting, dugoutcanoeing in the Lower Gorge (both with riversidecamping), photographic safaris, or guided ascentsof Gunung Leuser are potentially lucrativeindustries, which should be subject to properfeasibility studies. Such developments should beconsidered more than desirable: they should beconsidered essential to the future of GunungLeuser.

Despite its difficulties, Gunung Leuser as anational park is a triumph for conservation and alaudable achievement of world importance by theGovernment of Indonesia. Gunung Leuser's7900 sq km are sufficient to sustain genetically110

viable populations of several vanishing species,including orang-utans, tigers and rhinos. It is to behoped that it is also large and healthy enough toresist the kind of catastrophic damage sustainedby forests in East Kalimantan due to drought andfire in 1983 {Asiaweek, 1984). It acts as animportant watershed, which is critical for agri-culture downstream, provides numerous otherservices including climate moderation and carboncycling (Woodwell et a/., 1983), and is a store-house of genetic diversity; the uses of many of itsspecies remain to be assessed.

References

Asiaweek Staff. 1984. Wound in the world. Asiaweek. July13. 32-55.

Aveling. R. and Mitchell. A.H. 1982. Is rehabilitating orang-utans worthwhile? Oryx, 16, 263-271.

Blouch. R.A. 1984. Current Status of the Sumatran Rhinoand Other Large Mammals in Southern Sumatra. WorldWildlife Fund: IUCN/WWF report no. 4. Project 3033 fieldreport.

Caufield. C. 1984. Pioneers of the outer islands. NaturalHistory, 93(3), 22-32.

Frey. R. 1978. Management of orang-utans. In WildlifeManagement in Southeast Asia (Eds J.A. McNeely, D.S.Rabor, and E.A. Sumardja), pp. 199—217. Biotrop.,Bogor, Indonesia.

Ghiglieri. M.P. 1984a. The Chimpanzees of Kibale Forest.Columbia University Press. New York.

Ghiglieri. M.P. 1984b. The mountain gorilla: last of a vanish-ing tribe. Mainstream, 15,3-4, 36-40.

MacKinnon, J. 1974. The behaviour and ecology of wildorang-utans (Pongo pygmaeus). Anim. Behau. 22,3—74.

Martin, E.B. 1983. Rhino Exploitation in India, Indonesia,Malaysia, Burma, Japan, and South Korea. World WildlifeFund, Hong Kong.

Mitchell, A.H. 1984. Primate Conservation and the GunungLeuser National Park. Indonesia. IUCN/SSC PrimateSpecialist Group Newsletter no. 4; 40—41.

Myers, N. 1984. The Primary Source. W. W. Norton. NewYork.

Rijksen, H.D. 1978. A Fieldstudy on Sumatran Orang-utans(Pongo pygmaeus abelii Lesson 1827) Ecology, Behav-iour and Conservation. H. Veenman & Zonen B.V.,Wageningen, The Netherlands.

Rijksen, H.D. 1982. How to save the mysterious 'man of theforest'?. In The Orang-utan. Its Biology and Conservation(Ed. L.E.M. de Boer), pp. 317-341. Dr W. Junk, TheHague.

Van Strien, N.J. 1978. Management Plan for the ProposedGunung Leuser National Park. World Wildlife FundReport.

Woodwell. G.M., Hobbie J.E.. Houghton. R.A.. Melillo. J.M.,Moore. B.. Peterson. B.J. and Shaver. G.R. 1983. Globaldeforestation: contribution to atmospheric carbondioxide. Science. 222,1081-1086.

Michael P. Ghiglieri. 814 N. Leroux, Flagstaff. AZ 86001,USA.

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