ORIGINAL ARTICLE

Franck Lavigne Æ Yanni Gunnell

Land cover change and abrupt environmental impacts on Javanvolcanoes, Indonesia: a long-term perspective on recent events

Received: 9 May 2005 / Accepted: 7 September 2005 / Published online: 11 February 2006� Springer-Verlag 2006

Abstract Based on a presentation of the spectacularlyabrupt environmental and societal processes occurringon Java since the 1990s, and using that as an analogue tocompare their consequences with the known environ-mental history of the island, we unravel the relativecontributions of natural and human impacts in shapingthe environment of Java. Our work is based on remotesensing, Geographical Information System analysis,field-based observations and measurements of responsesto abrupt land cover changes in the last 10 years. Eco-logical disturbance has been endemic to the long-termhistory of Java, but montane forests on volcanoes havesince ca. 1990 become the last frontier of colonisationand are for the first time rapidly receding. We revealhow human disturbance of natural ecosystems, today asin the past, tends to be the greatest where resistance isthe least. This appears true within the regional setting ofSoutheast Asia, where Javan forests since the last gla-ciation have constituted a biogeographical ecotone witha limited natural ability to regenerate after someimbalance. It is equally true at the scale of single eventswhere humans will turn a natural disturbance to theirown advantage. Overall, it remains difficult to decon-volve the signals of spontaneous human impacts and oflocalised natural events such as volcanic activity, ElNino-related forest fires or longer climatic anomaliesbecause humans are opportunistic in their attitudes tonatural variability and so the two are often inextricablylinked. The clearest impact on land cover and landdegradation comes from the history of state-organiseddeforestation, whether colonial or indigenous, becauseits impact has been systematic, pervasive and regionallyconsistent. Javan environments have shown astonishing

signs of resilience under the abrupt, cumulative impactsthat have been inflicted over the last four centuries insuccessive iterations, possibly because the high-energytropical and volcanic environment is a system in whichsediment turnover is naturally rapid and where pastscars of land degradation either heal rapidly or are soondestroyed by younger events. However, the volcanoesare the island’s keystone reservoirs of water, sedimentand biodiversity and command the geomorphic metab-olism of the lowlands. By removing forests fromincreasingly crowded mountain slopes, Javanese societyis following a trajectory in which new nonlinear re-sponses to environmental hazards and change may limitour capacity to anticipate and contain environmentalrisk to human life and property.

Keywords Volcanoes Æ Land cover Æ Landdegradation Æ Ecotone Æ Natural hazards ÆEconomic crisis Æ Nonlinearity Æ Java

Introduction

Most studies of Indonesian forests have focused onOuter Indonesia, where 97% of forests are found (e.g.Whitmore 1981, 1984). The island of Java, in contrast,represents Inner Indonesia: only 7% of the land areaand 3% of the forest, but 67% of the population. Itsagroeconomic and environmental identity are entirelydifferent: dominated by rice and sugarcane, Java isprobably the most accomplished exemplar in the Tropicsof state-organised timber mining and abrupt environ-mental destruction, where ‘scientific’ forestry spawned inengineering schools of France and Germany wasimplemented by Dutch colonisers after 1796, refined,and soon exported to other forested regions of theTropics (Peluso 1992). Although 23% of Java remainsclassified as state forest (7% protected or reserved, 16%for production), much of it involves plantations, andtherefore low richness, low diversity and a single canopylayer. As such, and given that ecological complexity is

Electronic Supplementary Material Supplementary material isavailable for this article at http://dx.doi.org/10.1007/s10113-005-0009-2 and is accessible for authorized users.

F. Lavigne (&) Æ Y. GunnellLaboratoire de Geographie Physique, CNRS UMR 8591,1 Place Aristide Briand, 92190, Meudon, FranceE-mail: lavigne@univ-paris1.fr

Reg Environ Change (2006) 6: 86–100DOI 10.1007/s10113-005-0009-2

commonly believed to be a major attribute of ecosystemresilience, Java is to many analysts a shocking epitomeof the deleterious ecological effects of agricultural andforestry monocultures. These carry all the potentiallydisastrous consequences suffered by simplified ecosys-tems in terms of vulnerability to pests through loss ofbiodiversity, and of flood hazards, slope instability, andsoil erosion.

The link between land cover change and land deg-radation is strong in most environments. Investigatingland cover change, however, requires discernment, aswoods do not cease to exist simply by being felled anymore than a meadow ceases to exist after a crop of hay(Rackham 1986). Asking why a wood disappeared doesnot directly address why it did not grow again. Linkingknowledge of the past with processes of the present liestherefore at the borderline between political economyand the environmental sciences, and requires an exami-nation of both historical and geological archives. In thispaper we do both, our basic hypothesis being thatwoodland increases infiltration over runoff, so defores-tation modifies runoff coefficients and hence affectssedimentary systems on slopes and in river floodplains ina specific and recognisable way. Based on a presentationof the abrupt environmental and societal processesoccurring on Java since ca. 1990 and using that as ananalogue to compare those impacts with the knownenvironmental history of the island, we attempt to un-ravel the relative contributions of natural and humanimpacts in shaping the environment of upland Java. Theisland being highly susceptible to natural geomorphichazards, we track whether the geomorphic scars of landcover change have followed recurrent patternsthroughout the Holocene, or whether the environmentalstigma recorded in the late twentieth century are uniqueand unprecedented. We also evaluate whether thecumulative environmental impacts through time havehad lasting systemic consequences on the geomorphicsystems of Java, or, given the literature on the aston-ishing resilience of Javanese society (particularly, its wet-rice agro-ecosystem: Geertz 1963), whether we are alsodealing with a particularly resilient environment.

Methods

Although the surface covered by the remaining forests ofJava has decreased drastically in most parts of the islandsince the 1990s, data to substantiate this and reports oncollateral geomorphic and hydrological impacts ofdeforestation are rare. When they exist, their accuracy isdoubtful because they come either from unpublishedreports of the State Forest Corporation (SFC), whichhas a vested interest in underestimating clear-felling offorests under its responsibility, or from journalists. Herewe present first-hand data on deforestation rates basedon satellite image processing and subsequent spatialanalysis at the regional scale using a Geographical

Information System (GIS: ArcView�). Forest recessionwas studied through a combination of aerial photo-graphs (1993), panchromatic Spot images (1997) and aset of multispectral Spot and Landsat TM images (1979,1991 and 2001) of Mts Sumbing and Sindoro. We sys-tematically applied the same image processing protocolto several other volcanoes in Central Java, includingDieng, Merapi, and Merbabu, and Mts Welirang, Ar-juno, Kawi, Anjasmoro and Semeru in East Java(Fig. 1). Image processing was completed at each site by12 months of field surveys, carried out during the rainyseason and spread over the period 1999–2003, in orderto update the land cover data, complete our databaseand assess the geomorphic and other environmentalimpacts of abrupt deforestation on the ground. Thisinvolved collecting existing hydrological, climatic andgeomorphic data from local offices (PT Jasatirta: Ma-lang; Brantas Project: Surabaya; PT Indonesian Power:Banjarnegara; BRLKT and BCEOM: Yogyakarta;BPTDAS: Solo); and acquiring first-hand data throughfield measurements of soil erosion, sedimentation inreservoirs and river suspended loads (Cimanuk, Serayu,Progo, Brantas, Konto, etc.). We also studied the con-text and impacts of several deforestation-related disas-ters that occurred between 1999 and 2003.

Results

Abrupt clearance of forests on Javan volcanoes sincethe 1990s

Observational evidence

With ca. 120 million inhabitants and averages of 700–900 people per square kilometre on agricultural land inhill areas, Java is the most densely populated region ofSouth-East Asia and has maintained some of the mostintensively used agricultural land in the world for cen-turies. As a result, extensive tracts of sparsely inhabitedand unlogged forest are almost absent, except for a fewnatural forest patches protected as nature reserves(731,000 ha in 1990) and monospecific protection forests(419,000 ha in 1990). These are mainly located on thehigher slopes of the volcanoes. These forests are man-aged by the SFC, which is also in charge of 1.8·106 ha ofproduction forests in 1990 (Suwardi Machfud 1990).

Until recently, highland forest has survived due toremoteness and impracticalities of agricultural develop-ment. However, the montane forests have become thelast frontier of colonisation in Java as observed in thecontext of the 1997 economic crisis. Everywhere on theisland, forest clearance on the volcanic slopes hasreached its highest rates since the colonial period. Aclear example is given by the flanks of the Sumbing andSindoro volcanoes (Central Java), where the forestedareas have been declining since the late 1980s (Fig. 2).The forested area declined at a very low rate from 1979

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to 1994 (700 ha cleared). The accelerated recession be-tween 1994 and 1997 (7,100 ha lost in 4 years) is mainlydue to fires that occurred in Central Java in 1995. Since1997, high deforestation rates (�600 ha year�1) resultfrom the upslope expansion of tobacco fields by localfarmers. The trend is similar on the volcanic slopes ofEast Java where the forest areas drastically decreasedbetween 1990 and 2000 (Fig. 3).

Based on local-scale field enquiries, it is clear thatcurrent deforestation has not affected all types of forestequally. Private and communal forests (hutan rakyat)suffer little from logging. The principal victims ofspontaneous forest clearance are the state forests (hutan

negara) managed by the SFC. Protected teak forests inthe nature reserve on the slopes of Mount Welirang(East Java), for instance, are being rapidly thinned byillegal loggers. Some forests recently managed by theSFC have been converted to agriculture, as observed inthe Mondo river catchment north of Kebumen. Evenareas that were reforested at the end of the 1980s or atthe beginning of the 1990s through a Regreening Pro-gramme currently suffer from illegal logging. Forexample, the surface area of reforested slopes in theUpper Kali Konto Project (East Java) decreased from29,625 to 24,843 ha between 1994 and 2003, i.e. a loss of16% in 9 years (Boun Heng et al. 2004). In the mid-1990s, administrators of the Dieng Plateau in CentralJava received an award for the success of its reforesta-tion and land conservation plan. In 2000, 60% of the20,000 ha of forest in this region had already disap-peared (Guyomarc’h 2003).

Causes and mechanisms

The causes for late twentieth century deforestation onJava are unprecedented. The years 1997 and 1998 werea turning point for Indonesia. With a financial crisisaffecting the Far East, Indonesia sank into a deepeconomic and political crisis. The stock exchange cra-shed and the devaluation of the rupee caused manybankruptcies. This situation was worsened in Indonesiaby three aggravating circumstances. Firstly, the years1997 and 1998 recorded the strongest ENSO anomaly

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Fig. 1 Location of the main volcanoes and rivers (white lines) of Java, and sites mentioned in the text

Fig. 2 Decrease of the forest area on the Sumbing and Sindorovolcanoes since 1979 (after Texier 2003)

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of the twentieth century. The intense El Nino-generateddrought of 1997, followed by catastrophic La Nina-related floods in 1998, destroyed the food resources ofthe country, which had to import rice to prevent fam-ine. Secondly, the fall in oil prices by 30% compared tothe previous year caused a sudden state treasury deficit.Thirdly, austerity measures imposed by the Interna-tional Monetary Fund plunged the population deeperinto insecurity. Prices of consumer goods rose rapidly,triggering social unrest which ended in the fall of theNew Order regime of General Suharto. The politicalvacuum left in the wake of this regime change, orReformation, left the country in a state of socio-eco-nomic chaos. In the rural areas, impoverished farmersencroached on forest lands to grow subsistence crops.These efforts by villagers to illegally occupy the forestare the continuation of a civil disobedience traditionstarted during the colonial period (Peluso 1992), but in1997–1998 they were specifically driven by the lack ofaccess to land for farming, lack of employmentopportunities and low household incomes. Whereasforest clearance was a localised and discrete phenome-non at the beginning of the 1990s, after 1997–1998 itincreased in intensity everywhere in Indonesia, includ-ing the volcanic slopes of Java.

Different strategies were adopted by the peasants tomake arable land available on the upper slopes of vol-canoes. The easiest and least confrontational tactic wasnot to fight the El Nino-related forest fires in 1997.Newly burned slopes were used by the farmers forplanting subsistence crops even though the land was stillunder the jurisdiction of the SFC. We observed a similarattitude during the extensive fires that burned the stateforests on the slopes of the Merapi and Merbabu vol-canoes in October 2002. A second and more activefarmer tactic consisted in invading a state forest in order

to convert it to agriculture. Invaders were either localvillagers, as on the southern flank of Mount Sindoro, orexotic groups in conflict with the local farmers, as on thenorthern flanks of Mount Welirang (Chenet 2003). Inboth the cases, encroachment on state land remainsillegal.

The Reformation has been advertised by the media asthe main scapegoat for current environmental problems.However, in many upland areas, deforestation is not anew phenomenon. It is rather the acceleration of aprocess that has lasted for decades. Lands under thejurisdiction of the SFC and classed as protection forestsare called ‘‘disputed lands’’ (tanah sengketa: SuwardiMachfud 1990). This problem has been attributed toconflicts over production policies inherited since theSecond World War between the SFC, the Department ofAgrarian Affairs (Departemen Kehutanan) and individ-ual farmers (Peluso 1992). Illegally cultivated forests andestate lands on Java already covered >105 ha in the1980s (Palte 1989). This was conspicuous on military-owned land, where farmers are allowed to cultivatecertain tracts. In other areas called magersari lands(lands made temporarily available by the state), toler-ated forest camps are converted by landless farmers intopermanent settlements. These fait accompli end up beingunofficially accepted by the SFC.

Since the 1980s, the traditional subsistence crops andcoffee plantations in the upper and mid-slopes of vol-canoes have progressively been transformed into anagricultural production system dominated by commer-cial crops (sugarcane and tobacco). During colonisationthese were mainly confined to the low-elevation flood-plains. Nowadays, apple orchards cover the slopes of MtArjuno near Malang, potatoes have become a mono-culture in the Dieng caldeira, and tobacco fields reachtheir thermal limits on the slopes of the Sumbing and

Fig. 3 Forest recession in theBrantas watershed between1990 and 2000. This GISthematic map results from aspatial analysis based on twocolour composite Landsat TMsatellite images

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Sindoro volcanoes. As a result, subsistence crops havealso been progressively pushed upslope towards thesteeper areas, with poor terracing or shelter plantingsystems and increased erosion hazards. This is the priceto pay for personal enrichment: in 2001, the averageannual takings of a potato planter at Dieng reached 26millions rupiah (i.e., �2,600€: Balai Teknologi Pen-gelolaan Daerah Aliran Sungai, 2002, unpublisheddata), which is equivalent to the annual income of auniversity professor in Indonesia. As in other mountainsof the Tropics, this phenomenon is related to the risingdemand in cool climate fruit and vegetables from cor-porate multinationals (potatoes on the Dieng Plateauare commissioned by, among others, Kentucky FriedChicken) and from the population in the rapidly grow-ing cities. The end of the 1990s is therefore marked by anunprecedented shift to highland farming on volcanicslopes above 1,200 m a.s.l. (Ruthenberg 1980; Palte1989; Nibbering 1997). By effectively ushering in theconversion of protection forests to agriculture on thedisputed lands at high elevations, the Reformation actedas an abrupt and significant increment in a secular trendof land degradation.

Environmental impacts of the post-1997 land cover crisis

Disturbances of physical resources

There are several examples in Java where it is proventhat forest clearing disrupts the climate at the local scale.On Dieng Plateau, e.g. frost during the dry season hasbeen reported for the first time whereas this phenome-non was still unknown at the beginning of the 1990s.Around Malang city, deforestation caused by urbangrowth has recently increased recorded daily maximumtemperatures. During the dry season, high deforestationrates increase the chronic water resource problem of thedry season related to the high permeability of volcanicsoils. For example, on the south flank of Mt Arjuno,spring discharge at the source of the Brantas, one of thelargest rivers in Java, recently decreased from 7 m3 s�1

to less than 1 m3 s�1 (P.T. Perum Jasa Tirta, oral

communication, 2002). As a result of high sedimentationrates, and due to water pumping for irrigation of thenew potato fields that have replaced the forests since2000, some volcanic lakes in the Dieng caldeira such asTelaga Balai Kambang or Telaga Swivi now dry outduring the dry season. This is unprecedented withinhuman memory.

Everywhere on the volcanic slopes in Java, erosionrates have increased significantly since the Reformation.Data from several experimental erosion monitoringplots have given rates of 50–60 t ha�1 year�1 in tobaccofields on the slopes of the Sindoro and Sumbing volca-noes. Rates reach 400 t ha�1 year�1 in potato fields onDieng Plateau (Guyomarc’h 2003). In 2002, calculatedsoils loss rates ranged from 4.21 mm year�1 in the upperSerayu catchment to 13.7 mm year�1 in the upper Me-rawu catchment, whereas rates in the 1990s neverexceeded 2 mm year�1 in either of those (Balai Reha-bilitasi Lahan dan Konservasi Tanah Opak-Oyo-Serayu,oral communication, 2002). Therefore, past affirmationsthat slope erosion rates in volcanic areas were up to tentimes lower than in the sedimentary hill zones of Java,where deforestation has historically been extreme (e.g.Karmono 1980), are no longer valid in the currentenvironmental context where accelerated soil erosion isalso affecting the volcanoes.

The hiatus between a temporary but abrupt socio-economic situation such as the Reformation, and thedefinitive impact this has on erosion systems and envi-ronmental balances, epitomises the dramatic situation ofthe Javan environment today: avoidable or reversibleeconomic instability generates lasting changes in thephysical environment. The high erosion rates in theupper volcanic catchments result in rapid siltation of thedownstream reservoirs, thus reducing their life span andleading to considerable financial loss. This has beenrecorded at the Sudirman reservoir on the Serayu River(Fig. 4), and in the reservoirs of the Brantas River: from1997 to 1999, the Sutami reservoir was filled by7.1·106 m3 of deposits (Perum Jasatirta, unpublisheddata). In the upper Konto watershed, the storagecapacity of the Selorejo reservoir decreased from42.8·106 to 36.5·106 m3 between 1999 and 2003 (Boun

Fig. 4 Sediment progradationwedge in the Sudirmanreservoir on the Serayu riversince its construction in 1989.The reservoir has accumulatedmore than 60·106 m3 ofsediments, which represents40% of the storage capacity(unpublished data from PTIndonesian Power).Sedimentation peaked in 2000(7·106 m3) at the onset of forestclearing on the rims of Diengcaldeira

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Heng et al. 2004). Resulting from high erosion rates, anincrease in suspended load has been observed in severalrivers such as the Konto, where daily data sampled atthe Selorejo dam are available since 1997 (Fig. 5). In thisriver, the increase in sediment discharge since the Ref-ormation is related to the increase in rainy season riverdischarge.

Figure 6 shows that this recent trend does not reflectthe hydrological evolution of the Konto River duringthe last half-century. Despite great discharge variationsin the Konto River, three main periods may be distin-guished: 1957–1982, when rainy season runoff was veryhigh relative to annual rainfall (related to a period ofdeforestation); 1982–1998, when, due to a period offorest recovery as part of the Upper Kali Konto Project(1979–1988), extreme discharges were subdued evenwhen annual rainfall was high; and post-1998 whenagain river discharges rose despite a decline in rainfall(renewed deforestation since the Reformation).

Increasing hazards and societal risks

Population densities have not only risen in cities but alsoon the volcanic slopes. Recent deforestation in Java hasthus increased both natural hazards and risks to humanlife and property. While some hazards occur chronicallythroughout the island, others are more specific to eitherthe western or eastern parts of the island. The high-energy Javan environment being naturally prone tofrequent catastrophic events, caution should be takenbefore systematically pinning on deforestation everydisaster that occurs each year because correlations arenot always supported by fact. Nevertheless, recent forestclearing by Madurese immigrants on the southern flankof Mount Semeru (Fig. 3) has increased volcanic haz-ards because pyroclastic flows and surges, and over-

flowing lahars, are no longer slowed down by trees.Flash floods often evolve into debris-flows, called banjirbandang, due to the high sediment supply from the clear-felled or only recently reforested slopes. The most recentdisaster related to this hazard occurred on the Cumplengriver in Pacet (Mt Welirang, East Java) on December 11,2002 (Chenet 2003). Transporting large boulders, thedebris flow destroyed a spa complex and killed 26bathers as a consequence of recent deforestation on thenorthern slope of Mount Welirang. This is consistentwith another large flash flood that occurred four yearsearlier (La Nina: 1998), while no event of this type hadbeen previously recorded within living memory.

Among the 970,000 ha of forests that cover WestJava, 50% are considered as critical lands by the SFC. Inthe wet environment of this region, major hazards andrisks are related to landslides: in 2001, 40 out of the 54landslide events that occurred in Indonesia occurred inWest Java. In 2002, landslides killed 71 people inIndonesia, 51 of those in West Java (Dr. Surono, head ofthe Geological Hazard Mitigation Division, Directorateof Volcanology and Geological Hazard Mitigation,2003, personal communication). In some specific geo-morphic contexts, a landslide that has dammed a deepvalley may trigger a mud or debris flow due to suddendam breaching. Such an event occurred on Mt Kelut(East Java) in 1994 and Mt Guntur in 2003. During thelast eruption of the Papandayan volcano in November2002, the water of three lakes ponded by landslides wassuddenly drained off after the lakes were filled bymaterial from a debris avalanche. The resulting laharprogressed downstream in successive pulses for ca. 9 hand destroyed 245 houses (Lavigne et al. 2003). In suchcases, the disaster results both from a natural event andfrom human recklessness as the landslides in that par-ticular chain reaction were caused by forest clearing.

In the drier lands of Central and East Java, landslidesare less frequent. Forest fires, partly of human origin,are the main cause of land cover change and the initia-tion of abrupt geomorphic processes. Illegal logging isresponsible for large gaps in the forest canopy, allowingthe rapid growth of fire-sensitive undergrowth speciesthat increase the vulnerability of the forest. As a result,the October 2002 fires (see Appendix S1) burned 500 haof forests at the Arjuno-Lalijiwo Natural Reserve, and300 ha on the slopes of Mt Merapi, where an additional1.2·106 m3 of water were lost as a consequence of springquelling (data from the Ministry of Forests).

In this environmental context, a few conservationmeasures have been implemented, such as the incitationof farmers to substitute tobacco for coffee trees on theslopes of Mts Sumbing and Sindoro, in agreement withthe SFC. Other soil conservation projects, for instance inthe upper Mondo catchment, involve reforestation pro-grammes. These are mostly based on the planting ofyoung pine trees (Agathis), occasionally mixed withnitrogen-fixing lantorogung (Leucaena leucocephala).However, such programmes are sometimes unsuccessful:in the summer of 1999, for instance, the regional Forestry

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Department of Cilacap district decided, in agreementwith the local population, to clear a teak forest in orderto replace it with pine trees. These are more lucrative forthe local people in the short term. All previous trees werelogged and replaced by young 30-cm-high pine saplingsand subsistence crops such as peanuts, cassava, sweetpotatoes and banana plants on steep slopes. Geomorphicimpacts were almost immediate: the first heavy rainfallfollowing the land cover change triggered several shallowlandslides (Fig. 7), and this has recurred every yearduring the rainy season since 2000.

Disturbance and resilience of Javan ecosystems:how the long view informs the present

The history of the Javan environment is one ofcumulative impacts in which successive iterations ofabrupt deforestation have intensified ecological disor-ders. The century 1830–1930 inspired what Geertz(1963) has called the ‘agricultural involution’ of Java:without changing its essential structure, the wet-rice(sawah) agro-ecosystem absorbed into its mould newcash-crop substitutions to paddy and adjusted bymaking its inner workings ever more complex (rota-tional cropping on rice fields). The engine of colonialprosperity was the apparently limitless labour force,but its resilience was, eventually, pushed to the limitsand to the detriment of subsistence paddy cultivation.The solution to relieving the strain on the lowlandsawah agro-ecosystem was either to emigrate (organisedTransmigration) or to turn to ever more intense tegaldry-cropping (crop-and-fallow dry fields on hillsides)on ever steeper slopes. As elsewhere in the Tropics,firewood cutting has been responsible for ‘illicit’deforestation as a consequence of coercive restriction ofaccess to forest resources by the state (Gillis 1988). Thepartitioning between perennials in the mountains(except for spices, grown in the swidden systems long

before Dutch colonisation) and annuals in the plainscontributed to accentuate the bipolar character of thebotanical landscape between the sawah and tegal agro-ecosystems. Tegal itself is a substitution by permanentcrops to the traditional ladang, or short-cycle swiddenplot, which today survive among limited ethnic groupsin remote hill areas of West Java, where the Dutchdemarcated tolerance areas rendered essentially unsus-tainable due to their small size.

Despite these impacts, it remains extraordinary thatno dramatic change of a systemic nature has been in-flicted on the Javan environment until very recently. Wenow discuss in greater detail the long-term trajectory ofland cover change on Java, and examine both why thatisland, rather than any other, became Inner Indonesia,and what the main distinctions are between human andnatural impacts based on past records.

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Fig. 6 Monthly discharge of the Konto river and annual rainfall atSelorejo dam since 1957 (after Boun Heng et al. 2004). Thedischarge curve shows a sinusoidal shape which reflects normalfluctuations between the rainy season and the dry season. Adetailed analysis shows a tendency towards an abatement ofextremes through time, contrary to the rain-related curve which

shows a clear increase of extremes since 1983. This sharp contrastbetween the hydrological and rainfall data is even more obvioussince 1998. The last 5 years were characterised by a regular drop inthe annual rain totals whereas flow discharges have tended to rise.The conjunction results from recent land cover changes in theupper watershed since the Reformation

Fig. 7 Shallow landslide occurrence after deforestation of a teakforest in Cilacap prefecture (Photo: F. Lavigne)

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Learning from biogeographical history and pre-colonialhuman disturbance

Palynology is widely used to reconstruct past floristicassemblages and obtain a measure of differences be-tween modern vegetation and past patterns of landcover. However, its potential as a tool for reconstructinglowland tropical floristic assemblages is limited on Javabecause most native lowland species have disappearedfrom the present-day vegetation. As no modern ana-logues of natural vegetation really exist, it remains dif-ficult from a study of the modern pollen rain to calibrateand characterise the ecological boundary conditions ofthe past through the use of transfer functions. The fewexisting studies of modern pollen spectra in lowlandlakes on Java (Beuning 1996; van der Kaars et al. 2001)show that the pollen signal essentially reflects localvegetation. Lakes with similar moisture regimes mayshow similar pollen spectra, but signals unique to indi-vidual lakes also exist. So, detecting the intensity ofhuman overprints on natural changes in land coverduring the past and understanding forward ecologicaltrajectories to the present on the basis of floristic indi-cators remains problematic due to the difficulty inextracting regionally meaningful signals out of diverselocal situations. Despite these difficulties, potential veg-etation types on Java have been reconstructed.

Historically, natural ecotones have fallen prey tohuman disturbance much earlier than biome core zones.Java seems to be no exception. Although the colonialand post-colonial impacts, examined later in the dis-cussion, were decisive in transforming the land cover ofJava, intrinsic reasons for its more rapid degradationthan in Outer Indonesia lie in its biogeographical posi-tion within SE Asia. Contrary to the two core areas ofperhumid and aseasonal equatorial rain forest in Sun-daland (to the north-west) and Papuasia (to the east),Java is characterised by a seasonal monsoon climatewith only one area of rainforest restricted to the westernuplands. The eastern part contains large enclaves ofsharply seasonal climates, which represent the western-most outposts of drier climates that prevail in theMoluccas and Lesser Sunda islands. In East Java,

rainforests thus only survive as isolated pockets on thesouth-facing slopes of elevated volcanoes where cloudspersist and rain is received from onshore winds. Theposition of Java at the periphery of the adjacent rainforest biomes is reflected in its sharing 21–37% of itsplant flora with all of the neighbouring biogeographicalisland groups (Whitten et al. 1996), and its natural for-ests are, relatively, species-poor (Backer and Backhuizenvan den Brink 1963). Given this ecotone status, thenatural ability for Javan forests to regenerate after someimbalance, whether natural or human-related, hastherefore probably long been weak. Climatic forcingduring the Pleistocene, as well as ENSO oscillationsduring the Holocene, may thus have affected Java moreacutely than Outer Indonesia. Most of all, humaninfluence at the beginning of the Holocene, which was aperiod of extensive land use involving patch dynamicscharacterised by biological diversity (Semah et al. 2003),was the greatest where resistance was the least, and itmay be no surprise that this insular ecotone was to be-come Inner Indonesia.

Potential vegetation types on Java have been recon-structed according to the conventional criteria of vege-tation series mapping (Fig. 8). Evergreen forest isconfined to West Java (<2 dry months, >2,000 mmrainfall). Dry deciduous forest, dominated by teak(Tectona grandis), occurs potentially only in East Javawhere rainfall <1,500 mm and the dry season exceeds6 months, but it is doubtful that any such woodlandremains on the island today (van Steenis and Schippers-Lammertse 1965). Where dominant species are reducedto Acacia tomentosa, Acacia leucophloea and Borassuspalms, the woodland is believed to represent regrowthon ancient fields abandoned during religious wars be-tween Hindus and Muslims prior to colonisation (vanSteenis 1961). Cemera (Casuarina junghuhniana) iswidespread above 1,400 m a.s.l.

Moist deciduous forest prevails under 4–6 drymonths and 1,500–4,000 mm of annual rainfall. It is alsodominated by teak but associated with Bombax, Dua-banga and Tetrameles (Whitmore 1984). Teak, which isnative to Myanmar but extends to India and Indonesia,may not be indigenous to Java. There is, however, no

Fig. 8 Natural biogeographical provinces of Java based onbioclimatic criteria commonly used in the Tropics (simplified afterWhitten et al. 1996). 1 aseasonal montane forest (>1,000 m a.s.l.),2 evergreen rain forest, 3 semi-evergreen rain forest, 4 seasonalmontane forest (>1,000 m a.s.l.), 5 dry deciduous forest and 6

moist deciduous forest. Moist deciduous forest is also referred to insome texts as ‘monsoon forest’ (Whitmore 1984). The evergreenforest core is fringed by an aureole of semi-evergreen forest(evergreen species mixed with a few deciduous species, 2–4 drymonths) on the drier north-facing slopes of the island’s mountains

93

doubt that its success, and particularly its numerousgregarious stands, is directly linked to two human-re-lated factors:

1. Firstly, its probable introduction around 200 AD byHindu colonisers. By 1000 AD, it is believed that up to1.5·106 ha of plots, initially cleared for agriculture,were replaced by teak after exhaustion of soil fertility(Whitten et al. 1996). The recession of forest taxacaused by human deforestation preceding Dutch col-onisation has been documented on the volcanic slopessurrounding the Ambarawa swamp in Central Java(Semah et al. 1992): in a context of long-term pre-cipitation decline, forest clearance occurred duringthe sixth century AD, followed by a definitive reces-sion in the early fifteenth century. Teak was thus anearly coloniser essentially for reasons of cultural andeconomic preference by pre-Dutch foreign settlers:teak stands, by filling the gaps already opened in theforest by indigenous shifting cultivators, caused thedynamics of gap rotation to progressively coagulate.

2. Secondly, the ecology of fire has played a major rolein the success of teak as its seedlings are both fire-resistant and grazing-resistant. If fire has probablybeen used for at least the last 1 m.y. (Semah 1986;Swisher et al. 1994), teak as a dominant species isdefinitely the result of at least two millennia ofdeliberate refinement through fire (refinement: for-estry term referring to assistance in the survival oftrees of a target species by selective removal of oth-ers). Furthermore, the outward spreading roots, highwater uptake and shade given by teak trees after ca.5 years affords them supremacy over competingwoody species—a natural form of liberation (forestryterm describing the freeing of a desired tree fromcompetition by increasing light and reducing rootcompetition). In sum, the Dutch apparently arrivedafter 1600 AD on an island where the estimatedpopulation was 3.4 million (Reid 1984) and teak wasalready dominant. Teak planting has constituted upto this day ca. 90% of the total Javanese timberharvest, but the establishment of Dutch plantationswas merely an additional, if brutal, increment in thelonger-term process of moist deciduous refinement.

Finally, the average upper limit of occurrence of allthe dominant forest types (evergreen, dry and moistdeciduous) is 1,200 m a.s.l. Teak itself does not prospermuch above 1,000 m. The elevation band between sealevel and 1,200 m corresponds to sedimentary plateauxaccreted during Cenozoic plate subduction and is his-torically that which has suffered most from indigenous,colonial and post-colonial deforestation. The limestoneplateaux (Gunung Sewu, Bojonegor, Blora), with shal-low soils and presumably more stunted trees, were thefirst to be entirely clear-felled (Lombard 1974). Except inCentral Java the high volcanoes had remained relativelyunscathed, so that the current distribution of naturalforests is highly skewed in favour of montane types.

Learning from a colonial history of timber mining

Records of past deforestation on Java prior to 1,800 aremeagre (Lombard 1974; Brookfield 1997). The king-doms of Mojopahit (fourteenth century AD) andMataram (seventeenth century AD), were major periodsof forest colonisation involving permanent agriculturalsettlement in large clearings. As in Europe, this devel-oped under the impetus of monastic influence. Java’shistory of land use since the early nineteenth century, incontrast, has been described extensively (Raffles 1817;Nibbering 1991; Palte 1984, 1989; Peluso 1992; Whittenet al. 1996). However, the main focus being on timber asan economic resource, the collateral impacts of defor-estation such as erosion and risk enhancement haverarely been addressed in detail. The population of Javawas 4.6 million in 1815 (Raffles 1817). Since its creationin 1602, the East Indies Company (Dutch acronym:VOC) had been conducting mercantile politics but directland cover disturbance was limited to a few mountainslopes covered by coffee plantations in West Java. After1810, land cover change in the uplands was not agradual clearing process but occurred in four main stepssummarised in Table 1. The three major stages are re-flected in the spectacular progress of river deltas aroundJava (Fig. 9). After peaking between 1897 and 1937(�22,000 km2 removed), deforestation brought naturalforest cover down to 23% in 1939, 11% by 1973(Donner 1987) and 7% of the surface area (0.96·106 ha)in 1990 (FAO 1990). As a result, very few natural foreststands survive anywhere in Java (Fig. 10) even though itremains difficult to track precisely which areas, foresttypes and altitudinal zones suffered most (Durand 1989).The Konto river catchment is one of the better docu-mented, where only 7% of the forest has remainedundisturbed due to its remoteness, but where theremaining 93% show stigma of long-term human dis-turbance with impacts on soil erosion and sedimentbudgets (Smiet 1992).

Awareness of the need for soil conservation appearedonly at the end of the colonial period, under pressurefrom the sugar industry. Due to a decline of canal irri-gation water caused by deforestation and reduced riverdischarge, the need for watershed management byreforestation (protection forests) was acknowledged inthe Forest Law of 1920 (Smiet 1990). Reforestation ofthe uplands therefore initially occurred as a consequenceof ecological stress experienced in the lowland sawahecosystems. Fast-growing, non-native tropical pines(Agathis) were planted mostly as protection forests onthe steeper and wetter south-facing slopes of the volca-noes as a soil conservation measure. These forests in thelate twentieth century have been the main source ofconflict (the ‘disputed lands’) between the state and localcommunities, although predominantly for the forestland rather than the trees themselves. An IndonesianRegreening Programme began in the early 1970s undergovernment control, involving the planting of furtherprotection forests and perennial crops on slopes, the

94

construction of check dams outside state forests, and ofSabo dams on the more active volcanoes to check lah-ars. Regreening has also been a focus of conflict (Peluso1992).

Indigenous agroforestry: the fingerprint of anenvironment inextricably linked to human disturbance

The blanket term ‘agroforestry’ covers a multitude ofcategories, the nearly extinct ladang being the indige-nous prototype. Involving the fallowing of natural trees,it must be distinguished from the tumpangsari system,which was introduced from Burma (taungya system) bythe Dutch in 1873 and involved the fallowing of plantedtrees in addition to rotational cropping. It has since the1970s evolved into a varyingly successful form of socialforestry. The penghijauan system, also a Forestry Ser-vice introduction, appeared as part of the post-colonialregreening policy, with intercropping of annuals andshort-lived perennials. Finally home gardens, ubiqui-tous around villages, represent a diverse intergrowth oftree and/or agricultural, and forage and/or green man-ure crops. The first official record of Javan home gar-dens defined as agroforestry systems dates back to acharter of 840 AD (Soemarwoto and Soemarwoto1984). The aspect of man-made forests (talun-kebun,literally: perennial-annual crops) of such garden com-pounds, even in sawah areas, as a persistent leitmotiv inthe landscape, probably reflects how ingrained the cul-ture of agroforestry is through its many derivatives andadaptations to increasing population densities and amarket economy (Soemarwoto 1984).

The upshot is that the multiple forms of agroforestryprobably make it impossible to treat the botanical het-erogeneity of past Javan forest vegetation as natural(Michon et al. 1983). Agroforests were until recentlyviewed by western forestry engineers as a primitive, pre-domestication stage of selected forest trees. New find-ings have shown instead that they represent a highlysophisticated domestication of entire forest ecosystemswith a bias towards multi-purpose trees through aprocess of long-term refining (Michon and Foresta1997). Case studies have shown it is possible to find upto 250 cultivated species (not counting varieties) on theterritories of single hillside villages of West Java (Ab-dullah and Isnawan 1980). Trees are subjected toindigenous horticultural techniques, designed to shortenthe period of improductivity and increase the growthrate of fruit, which appear to have evolved over milleniarather than years or centuries. It would thus be toosimplistic to reduce the colonial history of Javan foreststo a case of ruthless ravaging by the Dutch of virginecosystems that an environmentally aware indigenoussociety was engaged in the noble act of preserving.Conflict was over the political control of forest as aresource (Peluso 1992), whether to claim the treesthemselves or the land for agriculture, not over forestprotection for moral, aesthetic or spiritual reasons as weT

able

1Periodisationofcolonialim

pactsonJavanlandcover

Events

andim

pacts

Historicalperiods

Raffles

interregnum

and

WarofJava(1811–1830)

Compulsory

cultivationsystem

(CCS,orcultuurstelsel)

(1830–1915)

Corporate

plantation

system

(CPS)

(1880–1930)

Japaneseoccupation

(1942–1945)

Officialpolicy

New

taxes

andstatute

labourlaws

State-runmercantilism

commandeers

20%

ofbestvillagelandforcash

cropsandim

poses2monthsper

yearofforced

labour

1874AgrarianLaw:privateers

extendcoffee

beltinto

uplandsandsugarcrops

insawahanddeltas

Landscommandeeredfor

commoditycropsandfood

insupport

ofWWII

effort

Socio-economic

consequences

Flightofrefugeesto

thinly

populatedmountains

Continued

retreatto

volcanoes

New

roadandrailwaycuttings

Ruin

oflandmanagem

entsystem

s

Environmentalconsequences

(basedonwritten

eyew

itness

reportsandarchives)

Deforestationvolcanoes

inCentralJava:Dieng,

Sumbing,Sindoro,Merbabu

Intensificationofsawahecosystem

sContinued

clearingofDieng,

Sumbing,Sindoro,Merbabu

Deforestation(300,000ha)of

east

CentralandWestJava

(Kawahijen,Kelt,Preanger,...)

Destructionof200,000haofforest,

acceleratedsoilerosion

Note:compiled

from

Raffles

(1817),Junghuhn(1854),Nibbering(1991),Durand(1989),Hoek

(1992),Peluso

(1992)andSevin

(2001)

95

see in modern environmental campaigning. In the OldWorld, for instance in Medieval England, the word‘Forest’ (with a capital F) was primarily a land of deer,not a land of trees: Forests could be wooded, but notnecessarily so (Rackham 1986). The same seems to applyto Javan forests (Lombard 1974), where late into thenineteenth century big game hunting was an importantpastime among the indigenous nobility and the colonialaristocracy.

The forest is therefore, in most cultures, a resource,not a place of recreation where trees are valued as anantidote to urban lifestyles. Much evidence exists on thenegative connotations of forest in Javanese mentality(Lombard 1974; Whitten et al. 1996). Forest on Javadoes not have a high cultural value, so it is debatablewhether home gardens, for instance, which may haverepresented an indigenous resource pool and at times alast bastion of economic privacy and resistance againstDutch hegemony (Table 1), should in any way be viewedas an emblem of conscious ecological conservation. Insummary, it seems that the Dutch and Javanese unwit-tingly shared a common enemy: natural forests. As aproof of that, to this day the relict natural forests of MtsHalimun and Slamet have faced lower attrition ratesthan those at lower elevations partly due to inaccessi-bility, but mostly due to fear and legend. As such theyhave retained higher than average levels of faunisticbiodiversity.

With something that can be harvested almost dailyfor household subsistance or for cash, the total pro-duction of agroforestry is estimated to be higher and lesslabour-intensive and capital-intensive (no chemical fer-tilisers or pesticides) than sawah systems. Crucially,however, agroforestry has never been regarded by gov-erning establishments as a rational use of land andlabour, and hence never received any support. Self-suf-ficiency in agriculture is by nature contrary to the rein-forcement of the State, and forest-dependentcommunities lose more than they gain from centralisedstate control over forests, whether reserved or planta-tions (Blaikie 1985): the colonial and post-colonial his-tory of Java is a vindication of this.

Population, transmigration and deforestation

By the middle of the twentieth century, about 107 ha offorest, or some 80% of its original area in Java, had beenconverted to agricultural land (Smiet 1990). At the sametime, the population was multiplied by ten in 130 years(1815–1945). The correlation between population den-sity and forest clearing is therefore evident and the ideaadvocating the conquest of new arable land as a pro-vider of economic welfare has been widely used in thetwentieth century for justifying the politics of Transmi-gration, i.e. the organised rural colonisation and settle-ment of Outer Indonesia by 1.7 million Javanese farmersin the decade 1971–1980, as part of a state-sponsoredpolicy to reduce population pressure on Java and itsenvironment (Sevin 2001).

However, fundamental to understanding the currentconquest of the volcanoes as the last frontier of theJavan rural environment is the backlash of the settle-ment policy, which generated a return flow of at least 0.5million after 1980. Rather than being reabsorbed intothe rural web, the returning migrants settled in Jakarta(Repetto 1986). The urban population of Java has sincebeen growing twice as fast as the rural, so it is ironic that

0 4 kmCimanuk R.

Java Sea N

Rambutan R. SINDANG

INDRAMAYU

1974

185719171946

Fig. 9 Growth of the Cimanuk delta, north Java, during and sincethe colonial period (after Hehanussa et al. 1975). Given the rapidresponse of sedimentary systems to recent and well constrainedland degradation events (cf. Figs. 4, 5), progress due to increasedsediment discharge between 1857 and 1917 is clearly correlated hereto the compulsory cultivation system (CCS) period (Table 1), whilethe 1946 position of the coastline probably reflects further build-upcaused by the CPS and maybe also the Japanese occupation. Deltasof Central and East Java recorded equivalent or higher rates ofprogradation. Thick black lines indicate rivers (some channelised)

Fig. 10 Natural forest cover on Java in 1891, 1963 and 1987 (afterWhitten et al. 1996). Dramatic recession and fragmentation haveoccurred in less than one century. Timber plantations andreforestation schemes, however, are not represented but wouldalso count as woodland. These maps thus mostly reflect the threatof deforestation to wildlife habitats and biodiversity rather than togeomorphic stability. Patches of natural forest along the island’saxis coincide with areas on volcanoes sensitive to volcanic hazards,which themselves are a source of natural stability for forestvegetation

96

the current deforestation of Javan volcanoes is partly anindirect consequence of the failed Transmigration pol-icy, which was precisely designed to relax stresses on theeconomy and environment of Inner Indonesia. Thisphenomenon comes as an overprint on the longer-termdecline in labour use for paddy cultivation since thecolonial period, which has generated a surplus of land-less farming labourers that the rice sector is no longerable to absorb (Repetto 1986), and who must thereforeseek a livelihood elsewhere. By targeting the volcanoes,which dominate the geomorphic metabolism of theisland, the process of agricultural involution in Javaanalysed by Geertz (1963) has probably reached in thelast 5 years a point of no return.

Population growth and high rural population densi-ties are not, however, sufficient to explain the recurrentprocess of forest clearing. It has in particular been de-bated whether the Regreening Program, involvingplantation forests, has not simply continued the CCS(Table 1) by transposing it to the uplands. Restrictingaccess to land increases population pressure withoutreally avoiding encroachment by marginal farmers,conflict with the authorities, and social unrest (Peluso1992). It seems, therefore, that post-independence Javahas continued to fulfil the prophecy of agriculturalinvolution (Geertz 1963): farmers are having to evolveever more intensive forms of agriculture while momen-tum for developing non-farm employment through thepromotion of indigenous entrepreneurship in craft andindustry is minimal (Repetto 1986).

Disorder in the Javan landscape: synthesisand perspective

Knowledge of pre-disturbance states on Java is limitedbecause few undisturbed analogues have survived. Thelong-term perspective given by the foregoing overviewconfirms that the current situation of accelerated envi-ronmental change on volcanoes has no clear-cut ana-logue in the past. Discriminating the frequencies ofhuman impacts from the periodicities of natural distur-bance regimes is made difficult by the fact that high-magnitude, externally driven natural processes involvingslope and river channel instability occur episodically evenin the intensively managed Javan agro-ecosystems oftoday. The high-energy Javan environment is a system inwhich sediment turnover is rapid and where past geo-morphological scars either heal rapidly or are soon de-stroyed by younger events. The ‘‘normal’’ state of natureon Java is to be recovering from the last disaster, notequilibrium and repose. Given this chronic state of dis-equilibrium, our short-term data is confirmed by thelonger-term evidence that human impacts and naturalphenomena are often inextricably linked, humans beingopportunistic in their attitudes to natural variability:El-Nino-related fires are used to expand upland agri-culture; juvenile volcanic debris are soon co-optedto agricultural land; prograding deltas, supplied by

sediment loads sourced by soil erosion in the hinterland,are developed into polders; river channel banks aredeliberately eroded by farmers to extend agriculturalland in floodplains (a practice called ngagugur: Diemontet al. 1991). The implication is that palaeoenvironmentalresearch on Java is faced with a chicken and egg problem,as any sedimentary archive (debris flow deposit, landslidescar, etc.), although generally recognisable on the basis ofdiagnostic criteria, cannot be unequivocally attributedeither to a natural cause or to a human-related distur-bance. Studying land cover changes in the Late Glacialand earlier, where charcoal levels are not matched withtell–tale pollen indicators of food crops or weeds, Vander Kaars et al. (2001) have also expressed uncertaintyover whether open vegetation around the Rawa Danauswamp (West Java) and the Bandung palaeolake wascaused by forest clearance, or whether people occupiedthe lake shores after vegetation had become more opendue to natural fires or climate change.

The known impacts of colonial land degradationwere soil erosion, increased river suspended sedimentloads, reduced dry season baseflow and rainy seasonfloods. Towards the end of the CPS period (Table 1),lowland farmers expressed complaints of diminishedbaseflow in Central and East Javan rivers during the dryseason. This record clearly agrees with trends (cf. Fig. 6)detected since 1997 by our own study of the Konto river.Although high evaporation in evergreen forests maydampen discharge potential, changes in land use otherthan forest/crop ratios (e.g. urbanisation) may changerunoff coefficients (e.g. Bruijnzeel 1982; van der Linden1983), and catchment size should control hydrologicalbehaviour, the generality of reduced river dischargeirrespective of catchment size clearly confirms the fun-damental role of forest cover on Javan volcanoes as afactor of infiltration and delayed supply of river flow bywater tables during the dry season.

Our characterisation of environmental change in thelast 10 years reveals that changes occurring as a conse-quence of periodic (e.g. ENSO) rather than exceptionalexternal forcing factors can be pushed over criticalthresholds by human design. Ensuing changes attainmagnitudes that are not commensurate with the mag-nitude of the initial triggering cause. Palaeoenviron-mental evidence of a vegetation change, or the onset ofan erosional episode, may not necessarily imply a majorchange in climate, land use or other forcing factors, butmerely critical threshold breaching of an unstable systemin response to a small, short-term perturbation such asfire, a severe storm or a major volcanic hazard. This isan expression of nonlinearity in natural systems (Phillips2003) that has remained elusive in the proxy analysis ofpalaeoenvironments, where change has overwhelminglytended to be interpreted in terms of external forcingwithin stable systems rather than nonlinear bifurcationwithin unstable systems. Consequently, in man-managedecosystems of the past, it remains difficult to unravellinearity from nonlinearity unless the natural andhuman (e.g. social, economic) settings are equally well

97

documented. This close link between natural factors ofenvironmental change and humans immediately ampli-fying a disturbance to their own advantage is probablyeven more true in the more distant past when the tech-nical means to disrupt natural balances were limited:cultivation of forest land probably made most progressin the wake of ENSO-related fires, and permanent teakplanting took advantage of existing swidden clearings.Awareness of such problems of interpretation of theenvironmental record is fundamental to ensuring thatwhat we learn from the past is not just a matter ofarbitrary perception or prescriptive prejudgement ofwhat is or is not disorder in the landscape.

The basic difference between natural and man-madeenvironmental disturbances in the long term is thatnatural disturbances essentially have local impacts (e.g.a lahar, a pyroclastic flow, a flood, a forest fire; ash fallwill cover wider areas but is beneficial to agriculture andpresents a limited risk to human life and property). Incontrast, human transformations can be designed andorganised in a systematic way to impact widely upon avast territory, as clearly illustrated by four centuries ofDutch and Indonesian resource mining. Traditionalshifting cultivation, as a form of local and transientimpact on the land cover, mimics the local impacts ofnatural instability. A study (1926–1933) apparentlynever repeated (cited in Whitmore 1984) involvedclearing small (0.1 ha) gaps in primary forest on MountGede in West Java. It was shown that such ladang wererapidly recolonised by surviving young individuals ofprimary forest trees. Meanwhile, in larger gaps of0.2–0.3 ha, which may represent a critical thresholdbetween the ladang (better suited to maintaining long-term ecosystem steady states) and clear-felling, the pri-mary forest trees were replaced by a dense growth ofsecondary forest pioneers. This example shows theimportance of thresholds in impacts on botanical sys-tems. The unprecedented problem generated by defor-estation of the volcanoes is, specifically, that due to theirtopographic supremacy and position on the island’sdrainage divide, a small or local change on any of themmay provoke regional repercussions out of proportionwith the size of the initial disturbance.

An interesting perspective to this history of defor-estation is that the state of land cover attained onJava today is similar to that of England (Fig. 11),where the decline of wildwood (i.e. natural woodlandunaffected by Neolithic or later civilisation) over thelast 5,000 years is well documented (Rackham 1986):80% of the original forest was lost by 2000 BP, fallingto <10% during the last 700 years. To this must beadded the impact of fragmentation, with less than 2%covering areas exceeding 100 ha (Spencer and Kirby1992). England and Java are the same size, but pop-ulation is nearly treble in Java and far more rural inproportion. Despite sharing similar levels of land coverloss, the biological impacts of fragmentation have beenfar greater on Java as natural biodiversity was initiallymuch greater. By contrast, however, the severity of

geomorphological and sedimentological impacts iscomparatively greater in England because the Javanlandscape has a greater capacity to adjust to brutaland sometimes radical changes following a great dis-turbance. Large-scale volcanic eruptions affect the re-gional climate, destroy the surrounding vegetation andincrease river sediment loads for years to decades.With >5070·106 m3 of ash deposited across Javaduring the last 100 years, however, andesitic volcanismalso boosts soil fertility and the vegetation rapidlyregrows in the warm humid environment. Meanwhile,soil erosion in England operates at the expense of anon-renewable stock of relict superficial deposits(loess, etc.) inherited from the ice ages or earlier. Withits rapid sediment turnover and dynamic slopes andriver channels, the geomorphic metabolism of Java ismore spectacular and exposes the population locally tomuch greater risk, but it has sustained far greaternumbers of people. With the widespread conservato-ries of engineered biodiversity in the form of homegardens, it is also debatable whether the overall impactof deforestation on Javan ecosystems as human life-support systems is more threatening than in the Eng-lish context. Historically, English society found outletsto domestic problems relating to the sustainability ofresources through colonisation and emigration. TheTransmigration programme to Outer Indonesia, al-ready practiced during Dutch rule, is a similar re-sponse to the problems of Inner Indonesia. This,however, has now come to an end due to strenuousresistance by host populations to ‘‘Javanisation’’.

Montane forest (> 1000 m a.s.l.)

1600 1700 1800 1900 1990

% o

f tot

al la

nd a

rea

JAVA: Time (years AD)

Cultivated land (sawah, tegal)

Lowland forest(< 1000 m a.s.l.)

Teak forest

Estates

Non-teakplantationforest

1600

3000 BC 2000 1000 0 1000 2000 AD

0

50

100

ENGLAND: Time (years)

1 23

4

Fig. 11 Decrease of forest area and land use changes on Java,1600–1990, and in England in the last 3,000 years (after Smiet 1990and Whitten et al. 1996). Dashed line refers to England, othercurves to Java. 1 Roman invasion, 2 increase due to growth ofsecondary woodlands, 3 Domesday survey and 4 beginning ofwoodland planting. The levels of natural forest decline are similarfor these territories of ca. 130,000 km2, but in Java decline occurredca. eight times faster. Lowland forest has suffered most, teak foresthas been maintained by management, while montane forest, thelast frontier of colonisation on Java, has survived relatively betterdue to remoteness, impracticalities of agricultural development andsuperstitious avoidance

98

So, in the twenty-first century the last frontier of InnerIndonesia lies within Java itself.

Conclusion

Javanese society has known nothing but restricted forestaccess imposed by the Dutch, the Japanese and its owngovernment. Java’s key non-renewable resources are itsoil and its volcanoes. Macroeconomic prosperity comesfrom the oil wealth, situated offshore, but this fluctuateswith global oil crises. In the early 1980s, an oil crisissimilar to the Reformation occurred, but the Transmi-gration policy was still an outlet that indirectly preservedthe Javan highland environment from abrupt defores-tation. Considering the fundamental function of thevolcanoes in the topographic configuration and hy-drogeomorphic metabolism of the island, it is unlikelythat the ongoing deforestation is just another iteration inthe long list of cumulative impacts that have alreadyscarred the island. The volcanoes represent a smallfraction of the land area and of the remaining forest, butthe final blow that would consist in destroying it is likelyto bring about systemic change out of all proportionwith the magnitude and extent of the disturbance. Theprospect of treeless volcanoes implies that volcanichazards are no longer mitigated by the friction of trees,and maximised runoff coefficients increase the risk offlash floods and soil erosion. The systemic consequencesof this extreme situation are that the life span of dam-med reservoirs, which did not exist at the time of pre-vious (colonial) land degradation crises, is dramaticallycurtailed. Their purpose of hydrological regulation andwater storage is hence defeated. Furthermore, sedimentstorage in these man-made reservoirs causes a lastingreduction in sediment delivery to deltas, so that coastalerosion can be expected despite increased sediment yieldfrom the catchments.

We learn from the Javanese past that cumulativecausation through time has damaged but not irreversiblydisrupted the resilience of the Javan environment.However, its paddy agro-ecosystem is intrinsically moreresilient (Geertz 1963) than its upland ecosytems. Thismay explain why it has absorbed so many iterations ofabrupt land cover change, land degradation and agri-cultural intensification for so long. Our study has pro-vided some baseline insight into the endemic instabilityof the Javan environment and hence the inappropriate-ness of envisaging environmental management policiesbased on assumptions of steady-state equilibria.Knowing from the past that the volcanoes have neverendured large-scale deforestation is critical to ourunderstanding of current events. However, what we canleast predict or anticipate based on past knowledge isenvironmental risk to human life and property giventhat population growth and human occupation of vul-nerable sites (steep volcano slopes, floodplains) has at-tained unprecedented levels. In this no-analoguesituation, this is where the future is most uncertain.

Biosketches

Dr. Franck Lavigne: Reader in Geography, University ofParis 1, specialises in natural hazards and environmentalrisks in volcanic settings. After working on lahars onMount Merapi, he has extended his field research toquantifying hydrological and erosional processes on theJavan volcanoes in relation with recent deforestation.

Dr. Yanni Gunnell: Reader in Physical Geography,University of Paris 7, and member of the Institut Uni-versitaire de France. He works on bioclimatology, soilscience, quantifying past erosion and sediment transferrates, and studies human impacts on forest and waterresources in the Tropics.

Aknowledgements The authors thank the students who contributedto field data acquisition and processing: M. Boun Heng, P. Texier,E. Guyomarc’h, M. Chenet. We are also grateful to our Indonesiancolleagues for their help, in particular Prof. Sutikno (UniversityGadjah Mada) and Ir. Sumaryono (Sabo Research Center) andthank the Centre National d’Etudes Spatiales (CNES) and SpotImage for affording data at discount rates. John Dearing, SimonHaberle and an anonymous reviewer provided thoughtful reviewsof the manuscript.

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