Landscape Ecology13: 135–148, 1998. 135c 1998Kluwer Academic Publishers. Printed in the Netherlands.

The impact of shifting cultivation on a rainforest landscape in WestKalimantan: spatial and temporal dynamics

Deborah Lawrence1�, David R. Peart2 and Mark Leighton31Department of Botany, Duke University, Durham NC 27708-0339, U.S.A. (current address) and Department ofAnthropology, Harvard University, Cambridge MA 02138, U.S.A.;2Department of Biology, Dartmouth College,Hanover NH 03755, U.S.A.;3Department of Anthropology, Harvard University, Cambridge MA 02138, U.S.A.;�corresponding author

Received 7 September 1996; Revised 22 March 1997; Accepted 10 July 1997

Keywords:shifting cultivation, land-use change, deforestation, rainforest landscape, West Kalimantan, Indonesia

Abstract

To assess the role of shifting cultivation in the loss of rainforests in Indonesia, we examined the spatial and temporaldynamics of traditional land-use north of Gunung Palung National Park in West Kalimantan. We analyzed theabundance, size, frequency, and stature (by tree size) of discrete management units (patches) as a function of land-use category and distance from the village. Data were gathered from point samples along six 1.5-km transectsthrough the landscape surrounding the Dayak village of Kembera. Most land was managed for rice, with 5% incurrent production, 12% in wet-rice fallows (regenerating swamp forest), and 62% in dry-rice fallows (regeneratingupland forest). The proportion of land in dry-rice increased with distance from the village; rubber gardens (17%of the total area), dominated close to the village. The size of rubber trees declined with distance, reflecting therecent establishment of rubber gardens far from the village. Fruit gardens accounted for only 4% of the area. Frominterviews in Kembera and three other villages, we estimated rates of primary forest clearing and documentedchanges in land-use. Most rice fields were cleared from secondary forest fallows. However, 17% of dry-rice fieldsand 9% of wet-rice fields were cleared from primary forest in 1990, resulting in the loss of approximately 12 haof primary forest per village. Almost all dry-rice fields cleared from primary forest were immediately convertedto rubber gardens, as were 39% of all dry-rice fields cleared from fallows. The rate of primary forest conversionincreased dramatically from 1990 to 1995, due not to soil degradation or population growth but rather to changesin the socio-economic and political environment faced by shifting cultivators. Although the loss of primary forestis appreciable under shifting cultivation, the impact is less than that of the major alternative land-uses in the region:timber extraction and oil palm plantations.

Introduction

Shifting cultivation is frequently identified as the pri-mary cause of deforestation in the tropics (Myers1993; Riswan and Hartanti 1996) despite controver-sy about the ultimate causes of forest conversion.Because shifting cultivation is practiced by people liv-ing in or near the forest, it will have a continuingimpact on rainforests. To evaluate this impact, we haveassessed the rate of primary forest clearing associat-ed with shifting cultivation, explored the causes ofthis deforestation, and determined the ultimate fate of

cleared lands. Within this framework, we can properlyassess the role of shifting cultivation, both as a factorin the degradation and loss of tropical rainforests, andas a system of management for their conservation orrehabilitation.

In Indonesia, 1.2 million hectares (m ha) of trop-ical rainforest is deforested every year (FAO 1993).Selective logging disturbs an additional 1.2 m ha ofprimary forest per year, but this disturbance is not con-sidered deforestation, or permanent alienation fromforest use (Grainger 1984; FAO 1993). Deforestationfollowing logging is often blamed on shifting cultiva-

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tors, who are assumed to use logging roads to expandinto previously uncultivated areas. In the Philippines,however, Kummer (1992) demonstrated that failedeconomic development and extensive timber extrac-tion encouraged the expansion ofnon-shifting, small-scale agriculture. In Malaysia (Repetto 1988) andThailand (Feeny 1984), large-scale industrial agricul-ture replaced logged forest. Perhaps in Indonesia, asin the Philippines, much of the deforestation has beenwrongly attributed to shifting cultivation by the origi-nal, non-migrant hill farmers (see Collins et al. 1991;Riswan and Hartanti 1996).

Throughout the tropics, people who engage inshifting cultivation often exploit standing primary for-est for game, timber and other products, as well asclearing it for agriculture (Denslow and Padoch 1988;Poffenberger 1990; Anderson 1990). We distinguishshifting cultivation from other systems of “slash-and-burn” encompassing a wide range of land-uses thatrely on fire simply to clear rainforest for cultivation orfurther development. Under shifting cultivation, farm-ers return to clear and cultivate a patch after a giventime interval, whereas under some types of slash-and-burn they may never revisit the same patch.

In Indonesia, shifting cultivators create and man-age several types of secondary forest, in addition togrowing upland rice (e.g., Michon 1991; Padoch andPeters 1993; Salafsky 1994; Lawrence et al. 1995).Few households can establish all their land holdingsnear the village. Because household labor is limit-ed, travel time decreases productive work time. Thusdistant land is managed less intensively, even thoughthe effort necessary to avoid vertebrate pest damageincreases with distance. We hypothesize that the trade-off between productive work and travel influencesdecisions about the purpose, size, and location of dif-ferent forest types. These are the land-use decisionsthat have traditionally structured human-dominatedrainforest landscapes.

By necessity, traditional patterns of land-use arechanging in response to a changing economic, socio-political and ecological environment. These changesmay have profound implications for landscape scalepatterns of land-use, including the distribution of pri-mary forest, and they present major challenges to con-servation and development policy (Kartawinata et al.1984; Dove 1985a; Abell 1988).

A study of landscape dynamics, both spatial andtemporal, can elucidate the rationale behind land-use decisions by shifting cultivators. Furthermore, itshould allow us to predict both the effects of those

decisions on the landscape and the constraints onfuture land-use decisions. While studies on a region-al or global scale yield estimates of forest conver-sion for a wide area (e.g., Skole and Tucker 1993;Houghton 1994), detailed local analyses can be effec-tive in clarifying the context and mechanisms of con-version, which are important for a thorough under-standing of the dynamics of land-use and for effectivepolicy implementation (Dirzo and Garcia 1992; Ojimaet al. 1994). Ultimately, regional satellite-image basedanalyses should be integrated with ground based stud-ies of well chosen focal areas (Moran et al. 1994).

We restricted ourselves to a ground based casestudy because our primary purpose was to understandthe context, causes, and effects of deforestation ratherthan to monitor it on a large scale. We determinedthe rate of deforestation associated with shifting cul-tivation in an intensive study area. We examined theeffect of local management systems on secondary for-est structure, analyzing both the individual land-useunit (see also Lawrence et al. 1995) and the village-based landscape. We addressed the following ques-tions: 1) How much primary forest is cleared everyyear by shifting cultivators and for what purpose?2) What are the characteristics of the major land-usetypes found in the landscape under shifting cultivation(size, frequency, stage of development)? 3) How doesthe distribution of land-use types change with distancefrom the village? and 4) What is the future of the land-scape under shifting cultivation? Our simple and inex-pensive methods (interviews and long transects) couldbe widely applied for rapid assessment of landscapedynamics at a small scale, e.g., around national parksor timber concessions.

Methods

Study site

We conducted this study in the landscape surround-ing the Dayak village of Kembera in the SimpangHulu district of the Ketapang regency in West Kali-mantan, Indonesia (Figure 1a; note correction of thelocation stated in Lawrence et al. 1995). The areawas chosen for its location and history. Kembera isabout 25 km north of Gunung Palung National Park(GPNP, 90,000 ha), between the Gunung Juring For-est Reserve (GJFR, 10,000 ha) and an active timberconcession (60,000 ha). Markets are accessible in thewet season by boat (2–3 days roundtrip). Permanent

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village-based, long-fallow shifting cultivation and treecrop production have been continuous in this regionfor over 200 years in a system similar to that foundelsewhere in Kalimantan (Dove 1985b; Padoch 1985;Mackie et al. 1987; Inoue and Lahjie 1990). Com-mercial logging has occurred within 1–5 km of Kem-bera and nearby villages over the last 5 years. Overthis same time period, the GJFR boundaries have beenredrawn to include lands formerly claimed by the vil-lagers. Kembera and its neighbors thus fall within therealm of a potential buffer zone for conservation for-est (GPNP or GJFR) and production forest (the timberconcession).

From April 1991–April 1992, we conducted sur-veys in Kembera and the neighboring villages of Ban-jur, Keranji-Baya, and Jelutung (all Dayak villages,except Jelutung which was Melayu; Figure 1a). Thevillage of Kembera, inhabited by 475 people in 96households, was the largest of these. Lawrence etal. (1995) provide a detailed description of Kembera.With ca. 3500 ha of managed forest and agriculturallands, the population density of Kembera was ca. 14persons/km2 of cultivated land. The size of the othervillages ranged from 37–66 households, but the culti-vated areas were not quantified. Except for Jelutung,which was established 20–25 years ago, the villageswere established from 60–100’s of years ago.

Land-use/forest conversion surveys

To define major categories of land-use and to esti-mate transition rates among them, we conducted inter-views in all four villages in 1991–2, and we returnedto Kembera for follow-up surveys in 1993 and 1995.We interviewed 20–50% of the households (random-ly sampled) in Banjur, Keranji-Baya, and Jelutung. In1991, we sampled 29% of all households in Kembera(22 randomly selected households plus an additionalsix of eight trader households); 71% were sampled in1993 and 42% in 1995 (these were opportunistic sam-ples depending on the availability of residents at thetime of the survey). Respondents were asked what typeof forest they had cleared to plant the previous year’srice field, the disposition of the field after the rice har-vest, and other questions on local land-use classifica-tion and practices, forest use, marketing activities, andhousehold demographics. These discussions led to thedesignation of seven major land-use types, which wereconfirmed through observations in the field (Table 1).

Sampling the landscape

Managed land surrounding the village of Kemberawas sampled along six 1.5-km long transects arrayedin a stratified, random design. Managed land wasdefined as that which had been previously clearedand planted and was currently in use or lying fal-low. It included rice fallows (jamih in the Kember-an language orbawas in Indonesian), dry and wetrice fields (mu, payak/ladang, ladang payak), fruitgardens (kampung buah/tembawang), and rubber gar-dens (kebun geta/kebun karet). The only land-use typethat was not systematically sampled, nor encounteredon the transects, was the homegarden (pekarangan)although almost every house had one. Like fruit gar-dens, but generally much smaller in extent (< 500 m2)and stature (< 20 m), the homegardens contain food,ornamental and medicinal plants, and are restricted tothe area around houses.

Transects were placed perpendicular to the centralaxis of the village which was clearly defined by a footpath running east-west from the edge of primary forestin the mountains to the border of village lands down-river (Figure 1b). Sampling was centered on the 2 kmof this path that ran through the center of the village;2 km were added at either end of this central seg-ment. The transects were stratified such that one tran-sect originated within each km of the central axis, run-ning alternately north and south from this line. Withinthese spatially defined strata, transects were randomlyplaced. The 1800 ha area defined by the transect lay-out (6 km� 3 km) represents about half of the totalarea managed by the village.

At sample points every 25 m along the transects,we classified land within a radius of 12.5 m as one ofthe seven land-use types in Table 1. We also estimatedthe diameter at breast height (dbh) for the largest treeswithin this radius. Because stands of trees in man-aged land are dominated by an even-aged cohort thatbecomes established after the most recent clearing, thetree community within a land-use unit tends to be quiteuniform in stem size. This characteristic was useful fordefining patch boundaries. Successive points along thetransect that were classified as the same land-use typeand had like-sized tree communities were consideredas part of one patch or unit (i.e., originally cleared atthe same time). We further assumed that the mean sizeof patches was proportional to the mean length of thetransect traversing the patches. Transect-length wascalculated as the number of sequential points compris-ing one land-use unit (patch) multiplied by the dis-

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Figure 1. a) Map of Kalimantan with inset (to scale) showing location of the study area north of Gunung Palung National Park. b) Map of thestudy area, Kembera, showing the location of transects (n = 6), each 1.5 km long.

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Table 1. Characteristics of the seven major land-use types in Kembera.

Forest type Patch size Tree Basal area Characteristic vegetation

range, density of trees

mean � 10 cm � 10 cm

(ha) dbh dbh

(trees ha�1) (m2ha�1)

Dry rice fielda 0.6–1.5, 1.1 0 0 several varieties of upland rice with annual vegetables such aseggplant, cucumbers, corn, relishes, various greens; often cassa-va or rubber seedlings; no standing trees

Dry rice fallowb as above 523 23 tree community ranging from homogeneous to diverse (3–42spp/0.10 ha); often simple vertical structure with monolayer oftree crowns

Wet rice fielda 0.1–1.0, 0.5 0 0 several varieties of wet rice; no standing trees

Wet rice fallowc as above ca. 20 � 1 few woody shrub species sparsely distributed, mostly sedges

Fruit gardenb ca. 0.1–0.7, 0.5 406 58 diverse tree community (14–32 spp/0.10 ha); tree crowns in mul-tiple layers

Rubber gardenb ca. 0.5–2.0, 1.2 337 20 primarily rubber trees, often intercropped with fruit trees (3–15spp/0.10 ha); simple vertical structure unless natural recruitmentby rubber is advanced

Primary forestd 10,000 ha ca. 584 42 species rich tree community with complex vertical structure 23–35 spp/0.075 ha);

aThe sizes of dry- and wet-rice fields were determined by mapping currently planted fields (n = 11 for dry-rice, n = 8 for wet-rice). Meansize of rubber gardens was estimated by dividing the number of trees per garden (from interviews, n = 25 gardens, range = 60–300 trees)by the mean density per garden (217/ha[Lawrence 1996]). The size of fruit gardens (n = 30)was estimated by walking through gardens oralong their perimeters.bFor dry-rice fallows (18–30 yrs old, n = 11), fruit gardens (> 50–150 years old, n = 10) and rubber gardens (12–30 yrs old, n = 11),density, basal area, and species richness of trees> 10 cm dbh were determined from plot data (Lawrence et al 1995).cYoung wet rice fallows (ca. 3–10 yrs) were preferred for cultivation. Older wet rice fallows were not sampled; while abundant, thesewere seldom returned to cultivation. Density and basal area of woody vegetation in young wet rice fallows were estimated from visualtallies at each transect sample point.dData for primary forest are from 4 plots (each 0.075 ha) in Gunung Juring Forest Reserve, near Kembera. The area of primary forestaccessible to people in Kembera was estimated as the protected area within 15 km of the village (not including logged forest).

tance between points (25 m). By examining patterns inthe sizes of the largest cohort of trees in these patches,we assessed landscape-wide variation in the stature ofdifferent land-use types.

In analyzing the percentage of the managed land-scape in each land-use type, we excluded the sam-ples (11%) that fell in primary forest (see eastern-mosttransect, Figure 1b). To analyze the effects of distanceon the proportion of different land-use types, we per-formed a series of permutation tests. The null hypoth-esis was that the distribution of land-use types doesnot vary with distance from the central axis (our “neu-tral model” of landscape structuresensuGardner et al.1987). According to this null hypothesis, the observedsequence of patches along a transect is as likely as anyother, random ordering. Constraining the data to keepthe points that fell within a single patch together andto keep the patches within their original transect, werandomly ordered the patches of each transect 1000

times. For each such ordering, we calculated the meandistance from the central axis for patches of each typeand then calculated a mean for each type over all sixtransects. With these 1000 mean distances, we createda reference distribution of possible means. We com-pared the mean distance observed in the field againstthis distribution to evaluate the probability that a giv-en type was generally observed closer or farther awaythan expected. We computed P-values by counting thenumber of averages that were more extreme than theobserved average and dividing by 1000. We analyzedchanges in patch size and tree size by linear regressionagainst distance to the central axis.

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Figure 2. Allocation of managed land to different uses within1.5 km of the central axis of Kembera. n = 366 point samples along6 transects, each 1.5 km long. Primary forest (encountered on onlyone transect) accounted for 11% of total transect samples and wasexcluded from the data shown.

Results

Spatial patterns resulting from shifting cultivation inKembera

In 1992, 79% of the managed land (i.e., excluding pri-mary forest) was in current rice fields or secondaryforest fallows, 17% in rubber gardens, and 4% in fruitgardens (Figure 2). Dry-rice production accounted for65% of the sample; 4.6% of this dry-rice land (or 3%of the sampled area) was in current production. Non-irrigated wet-rice occupied 14% of the land of which14.3% was in current production.

For 94 patches encountered along transects inKembera, land-use types were non-randomly distrib-uted with respect to distance from the central axisof the village. Dry-rice was found farther away fromthe village than expected under the null hypothesisof no distance-dependence (p = 0.012). Wet-rice andrubber were found closer than expected (p = 0.042and p< 0.001 respectively). Only six fruit gardenswere recorded, with no significant trend in their abun-dance with distance. The proportion of land in dry-rice production increased from 47% within 0.5 km to75% more than 1.0 km away (Figure 3). In contrast,land in rubber production decreased from 38% with-in 0.5 km to 3% beyond 1.0 km. Wet-rice in Kem-bera (current fields and fallows) was limited to the areawithin 1.0 km.

Figure 3. Change in land allocation with distance for Kembera in1992. Values are percentages of transect point samples within eachdistance range that fell within each land-use category. Values fordry- and wet-rice include both active rice fields and fallows. Primaryforest in the sample was excluded.

The size of individual rubber gardens decreasedwith distance (p = 0.020), while that of dry-rice fieldsand fallows increased (p = 0.040). Neither the size ofwet-rice fields and fruit gardens nor the size of trees inrice fallows and fruit gardens showed any trend withdistance. The size of rubber trees decreased signifi-cantly with distance (p = 0.035).

Variation in forest stature across the landscape

Overall, managed forests in Kembera were composedof small to medium-sized trees, with the largest cohortof trees in a given patch rarely exceeding 50 cmdbh. When all types of forest (i.e., excluding currentwet- and dry-rice fields) were considered together, thelargest cohorts of trees were< 30 cm dbh in 75% of allpatches (Figure 4e). Very large trees were found onlyin fruit gardens (60–109 cm dbh, Figure 4d). In 52%of the rubber gardens, trees in the largest cohort were< 20 cm dbh (not yet productive); 40% of the gar-dens had trees 20–29 cm dbh (productive), leaving 8%with trees up to 49 cm dbh (senescent, Figure 4c). Fordry-rice fallows, which dominated the managed land-scape, the modal tree size class was 10–19 cm dbh(32% of all point samples, Figure 4a). Only 20% ofthe dry-rice fallows had a community dominated bytrees< 10 cm dbh; an additional 42% contained treesbetween 20 and 39 cm dbh, and 6% had trees between40 and 59 cm dbh. In contrast, 47% of the wet-rice fal-lows had trees< 10 cm dbh. Analysis of size structureconfirmed field observations of two distinct types of

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Figure 4. Size structure of trees in managed forest land. Values arepercentages of land in each land-use type whose largest cohort oftrees is within the size range indicated.

wet-rice fallow in Kembera. Forty-nine percent of thefallows encountered were dominated by sedges with afew woody stems; 51% were dominated by medium-sized trees and looked much like natural swamp forest.

Forest clearing and conversion: patch dynamicsunder shifting cultivation

Most households in the region farmed two rice fieldseach year, one wet and one dry. These fields werecleared either from primary forest (in the timber con-cession or in GJFR) or secondary forest fallows. In1990, over all four villages, an average of 17% ofdry-rice fields and 9% of wet-rice fields were cleareddirectly from primary forest (Table 2). The proportionof dry-rice fields converted from primary forest washighest in Keranji-Baya (32%), and lowest in Jelutung(8%), where the proportion of wet-rice cleared direct-ly from primary forest was highest (17%). In 1990,between 3 and 15 ha of primary forest were clearedper village, or an average of 0.18 ha per household in1990. The remaining fields, i.e., 68–92% of dry-ricepatches and 83–100% of wet-rice patches (dependingon the village), were established by clearing secondaryforest. The average fallow length in the area for fieldsconverted from secondary forest was 12.9 years fordry-rice and 2.7 years for wet-rice (20.5 and 3.5 yearsrespectively, in Kembera).

The second major transition between land-usetypes, besides the conversion from forest to rice, isthe creation of rubber gardens. Rubber gardens alwaysoriginate in dry-rice fields. In 1990–1991, half ofall dry-rice fields in the region were planted to rub-ber (Table 3). However, the conversion of rice fieldscleared from primary forest was much greater than thatof fields cleared from fallows. Across the four villagessurveyed, 97% (87–100%) of fields originally clearedfrom primary forest were converted to rubber, vs. only39% (13–50%) of rice fields originally cleared fromfallows.

In the focal village of Kembera, the rate of prima-ry forest conversion changed dramatically from 1990to 1995. In 1990–1991, only 11–15% of all dry-ricefields were cleared from primary forest (Figure 5a).Since 1992, the proportion of fields that were con-verted from primary forest increased, reaching 64% in1995. As a result, the amount of primary forest clearedby the village as a whole increased to ca. 58 ha peryear, or 0.61 ha per household per year. The lengthof the fallow for fields converted from secondary for-est showed no significant trend over the period 1990–1995, varying from 13–27 years, and averaging 19years for the 6-year period (Figure 5b).

The rate of establishment of rubber gardens alsoincreased in Kembera from 1990 to 1995. Kemberahad the lowest rate of conversion from fallows to rice

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Table 2. Origin of dry- and wet-rice fields north of Gunung Palung National Park in 1990: conversion fromprimary forest and secondary forest fallows.

Village Number of From From Primary forest Primary forest Mean

fields primary fallowa converted converted fallow

sampled foresta village total /household length

(ha)b (ha)c

Dry-rice

Banjur 21 3 (14%) 18 (86%) 9.6 0.15 12.9 (n = 14)

Keranji-Baya 19 6 (32%) 13 (68%) 12.2 0.32 12.5 (n = 12)

Jelutung 12 1 ( 8%) 11 (92%) 3.1 0.08 5.6 (n = 7)

Kembera 26 4 (15%) 22 (85%) 15.0 0.16 20.5 (n = 6)

Average – 17% 83% 10.0 0.18 12.9

Wet-rice

Banjur 3 0 3 (100%) 0.0 0.00 –

Keranji-Baya 7 1 (14%) 6 (86%) 2.0 0.05 3.7 (n = 6)

Jelutung 6 1 (17%) 5 (83%) 2.3 0.06 1.0 (n = 5)

Kembera 23 1 ( 4%) 22 (96%) 1.6 0.02 3.5 (n = 8)

Average – 9% 91% 1.5 0.03 2.7

aNumber, percent of fields converted.b Village total from dry rice = (Pr)(Ht)(Hd)(Ad) where Pr= percent of fields converted from primary forest torice (in table), Ht= total number of households in the village, Hd = percent of households farming dry rice, andAd = average size of a dry rice field. For Kembera, Ht = 96; Hd was estimated, conservatively, at 0.9, becausesample data were lacking. Ad = 1.13 ha. Village total from wet rice = (Pr)(Ht)(Hw)(Aw) as above, substitutingHw = percent of households farming wet rice for Hd(percent farming dry rice). In Kembera, Ht = 96; in Banjur,Ht = 66; in Keranji-Baya, Ht = 38; in Jelutung, Ht = 37. For all villages, Hw and Aw were estimated based ondata from Kembera: Hw = .82 and Aw = 0.46 ha.c Conversion per household = village total/Ht.

Table 3. Number and percent of dry-rice fields converted to rubber in 1990–1991, classified byoriginal forest type.

Village Cleared from Cleared from Overall

fallows primary forest

fields Converted fields Converted fields Converted

sampled to rubber sampled to rubber sampled to rubber

# # (%) # # (%) # # (%)

Banjur 16 8 (50%) 3 3 (100%) 19 11 (58%)

Keranji-Baya 12 5 (41%) 6 5 (87%) 18 10 (56%)

Jelutung 10 5 (50%) 1 1 (100%) 11 6 (55%)

Kembera 24 3 (13%) 4 4 (100%) 28 7 (25%)

Averagea – 39% – 97% – 49%

aAverage of percents, treating each village as an independent sample.

to rubber in 1990–1, but reached or exceeded the rateof conversion in other villages by 1992–3 (Figure 5ccompared with Table 3). The proportion of rubbergardens that were created in rice fields cleared fromprimary forest was similar to that in other villages,

and very high (> 80%) for the entire period. Becausethe number of fields converted from primary forestincreased, the total amount of land converted from pri-mary forest to rice to rubber increased as well (Fig-ure 5d).

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Figure 5. Changes in land-use dynamics in Kembera from 1990–1995. a) percent of dry-rice fields converted from primary forest;b) mean fallow length of dry-rice fields converted from secondaryforest fallows; c) percent of fields converted to rubber gardens;d) estimated amount of land converted to rubber (number of dry-rice fields� percent of dry-rice fields from primary forest� fieldsize� percent of fields converted to rubber). For c) and d)- - -originally cleared from fallows; — originally cleared from primaryforest.

Discussion

Deforestation: shifting cultivationvs. industrialland-use

In Kembera, over 50 ha of primary forest have been cutannually for several years, and much of this land hasbeen converted to rubber gardens (Figure 5). Kembera,Jelutung, and Keranji-Baya lie within a 60,000-ha tim-ber concession between GPNP and GJFR, along withthree other small villages. We estimate primary forestclearing in all six villages is around 200 ha per year.

The area disturbed annually by industrial loggingin this same area is probably 2–3.5 times that dis-turbed by shifting cultivation. In a 60,000-ha conces-sion, selective logging by the Indonesian TPTI sys-tem allows the exploitation of 10–17 blocks of 100 ha(depending on the density of harvested species; afterCurran and Kusneti 1992). Sixty percent of the forestis accessible to mechanized logging, and 70% of thelogged area is moderately to heavily disturbed (Can-non et al. 1994), resulting in substantial disturbance of400 to 700 ha of lowland rainforest per year. AcrossKalimantan, an increasing proportion of selectivelylogged forest is converted to monospecific plantations,as concessionaires turn to plantation forestry in lieu ofwaiting for a second cut under the selective loggingsystem. As in Malaysia and Thailand, disturbance dueto logging may ultimately represent a permanent lossof mature forest whether or not shifting cultivators arenear by.

An industrial oil-palm plantation on the easternborder of GPNP had planned to clear-cut and burn3000 ha per year from 1993 to 1997 (V. Suma, ex-mayor of Kembera, pers. comm.). If this deforestationwere evenly distributed over the entire lifetime of theoil-palm trees (ca. 25 years), it would result in the lossof 600 ha per year. This rate of deforestation is threetimes that of shifting cultivation and affects an areafour times as large.

In contrast to plantation forestry or industrial agri-culture, disturbance by shifting cultivation sharesseveral important characteristics with natural distur-bances due to tree falls, wind throws and small-scaleforest fires and landslides. With shifting cultivation,relatively small patches of disturbed forest are pro-duced at a low rate, dispersed non-uniformly in thelandscape, and distributed consistently through time.The disturbance associated with plantation establish-ment is not distributed evenly in time or space. Meangap size under shifting cultivation (ca. 1 ha) is signif-

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icantly larger than that found in primary forest (10–120 m2) and naturally regenerating secondary forests(80 m2; Yavitt et al. 1995 and references therein). Con-sequently, the grain of the landscape is quite different,and yet, percent open area is similar. In primary forest,1–7.5% of the landscape is in the gap-phase (see Yavittet al. 1995); primary rain forest in Indonesia is likelyto fall into the lower end of this range (Poore 1968).In 80-yr old, neotropical secondary forest, Yavitt et al.(1995) found 4.3% of the area in gaps; in this study ofshifting cultivation, we found 5% cleared at any onetime (Figure 2).

Despite recent increases in primary forest clear-ing, shifting cultivation, as practiced in the Kemberaregion represents a land-use alternative that minimizesthe extent of primary forest loss compared to industri-al timber extraction or plantation forestry. Will shiftingcultivation continue to have a relatively low impact onprimary forests? The answer depends on what factorsdrive primary forest clearing and whether their effectsare changing over time.

Causes of deforestation by shifting cultivators

The expansion of cultivated land into primary rainfor-est near Kembera has been caused by the desire foreconomic development and political security. The peo-ple of Kembera want the goods and services procuredwith cash, especially secondary education for theirchildren, health care and quality housing. They rely onrubber cultivation to meet their cash needs. Poor fami-lies can borrow land for rice cultivation. By traditionallaw, however, they may not convert this borrowed landto rubber; they must claim and cut primary forest forrubber cultivation.

The total area of productive rubber gardens (thosewith trees> 20 cm dbh) should increase by 40%from 1992 to 2002, assuming a conservative diame-ter growth rate of 1 cm per year (Lawrence, unpub-lished data). This increase far out-paces populationgrowth of approximately 2% per year (P. Kleinman,pers. comm.). Over the next five years, conversion torubber could decline considerably, at least temporar-ily, as labor becomes limiting. High rates of primaryforest conversion to rubber may persist, however, ifthe political environment does not change.

The most recent expansion of rice cultivation intoprimary forest, followed immediately by rubber cul-tivation, was the result of an organized effort to gaintenure over lands traditionally owned by the villagebut presently exploited by timber concessionaires. It

was a direct response to the threatened replacementof selective logging (natural forest management) byindustrial plantation forestry. The villagers believedthat monospecific plantations could not provide themwith the benefits of primary forest or selectivelylogged forest (e.g., locally useful and marketable tim-ber, habitat for wild game, and clean water). Ratherthan forfeit current and future use of the land, the vil-lagers decided to claim the land by planting rubber. ByIndonesian law, unmanaged fallows are not in use, andthus may be expropriated. In contrast, planted treessignify an “improvement” and indicate that the landis in use. Furthermore, rubber, like oil-palm or woodpulp, is a significant source of foreign exchange andrevenue for the national government. Thus, rubber gar-dens may be tolerated as an alternative to industrialplantations, but this remains to be seen.

Deforestation in Kembera is not a direct conse-quence of soil degradation caused by unsustainablecultivation practices (Kleinman et al. 1996), nor sim-ply a response to population growth. If land availabil-ity had decreased due to population growth, we wouldexpect some farmers to respond by clearing primaryforest to maintain adequate rice production. Others,however, are likely to have shortened the fallow periodof land already in cultivation because clearing primaryforest requires more labor than clearing secondary for-est (Freeman 1955). Where primary forest still exists,both responses to land scarcity should occur togeth-er. However, the increase in primary forest clearingin Kembera was not correlated with a decrease in fal-low length (Figure 5a, b), supporting our assertionthat deforestation is currently driven by political andeconomic factors and not primarily by ecological con-straints on rice production.

Considering the relationship between fallow lengthand primary forest conversion over a broad geograph-ic range reinforces this point. We combined data oneight villages in East Kalimantan (Inoue and Lahjie1990) with our data from West Kalimantan before landtenure became a major issue (1990–1). In general, lessprimary forest was cleared when the fallow period waslong (Figure 6). Despite variation in settlement histo-ry, population density, and proximity to major urbancenters none of the villages exceeded an apparent lim-it to this relationship between fallow length and pri-mary forest conversion. The striking exception to thispattern was Kembera in 1994–5.

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Figure 6. The relationship between primary forest clearing and fal-low length for eight sites in East Kalimantan (EK, Inoue and Lahjie1990) and four sites in West Kalimantan (WK, this study). Dashedline drawn by eye to indicate the apparent limit in the relationshipbetween fallow length and the percent of fields converted from pri-mary forest in a given village.� indicates villages close to majorurban areas.

Integrating rubber and rice in the landscape(ca. 1950–1992)

Although most rubber has been planted in fieldscleared from primary forest over the past five years,rubber has also replaced secondary forest fallows at alower rate, since ca. 1950. The spatial pattern result-ing from this replacement may reflect the hypothe-sized trade off between travel and productive work.In 1992, rubber dominated close to the village (Fig-ure 3) because efficient exploitation requires regular,but short (� 1/2 day) visits over many months. Onlyrecently did villagers begin planting rubber more thana kilometer from the village, as evidenced by the low-er frequency of rubber gardens and the smaller sizeof rubber trees further from the village. Rubber gar-den size also decreased with distance. Once villagersdecided to plant rubber farther away, they may havechosen to reduce future labor requirements of the pro-ductive garden by limiting its size. Alternativley, theymay have reduced the time invested in vigilance duringthe establishment phase when deer browsing is severe,especially at the edges of gardens far from the village.

Managing a distant rubber garden often entailsrelocating the household for several years (an optionwhich has been pursued in Kembera). In contrast, ricecan be cultivated further from the village (Figure 3)because households can move to the fields for daysor weeks if necessary during seasonal periods of high

labor demand. During these periods, they can pre-vent incursions from vertebrate pests such as monkeys,deer, and birds. Further, the effects of any crop loss-es are mitigated by the increased size of rice fields atgreater distances, as in other parts of Kalimantan (Jes-sup 1981; Dove 1985b; Mackie et al. 1987).

Implications of the expansion of rubber(1993–present)

Adding long-lived tree crops to subsistence farmingsystems inevitably results in an adjustment of the bal-ance among food crops, fallows, and forest. Becauseputting land into rubber means keeping it out of rice,the decision may ultimately affect both the rate atwhich primary forest is converted and the length ofthe fallow. Changes in either parameter would affectboth the composition of the landscape and its abilityto supply resources to the village.

Because both primary and secondary forest arebeing converted to rubber (Table 3), the land base fordry-rice cultivation diminishes every year. To meetfuture rice needs, either more land must be broughtinto cultivation or land-use must be intensified. Clear-ing primary forest in the reserve is already prohibited,and the villagers have agreed to respect the boundariesin exchange for input into defining them. Similar con-straints exist for land in the timber concession. Accessto this land will be more restricted if it is converted toa plantation. Villagers could look for additional landwithin their managed forest area, but they are unlikelyto clear fruit or rubber gardens. Land-intensive alter-natives are clearly needed.

The people of Kembera could shift from cultivat-ing both dry-rice and wet-rice to cultivating wet-riceonly, a trend already evident in other areas of WestKalimantan (Padoch 1985). Other options would beto shorten the fallow or to extend the cultivation peri-od. Shortening the fallow may not be a viable optionif soil fertility declines and fertilizer inputs are notavailable (Nye and Greenland 1960; Kleinman et al.1996). Extending the cultivation period beyond one ortwo years would require intensive weeding or the useof herbicides. Even if fertilizers and herbicides wereavailable, currently they are not affordable.

Alternatively, villagers could grow rubber in fal-lows, maintaining the traditional (non-rubber) fallowrotation of 15–25 years. However, rubber productionwould be curtailed after only 5–15 years. The clear-ing of existing, productive rubber to plant rice seemsunlikely. A fundamental shift to a more cash-based

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economy (in which rice could be purchased with rub-ber revenue) would reduce the amount of land need-ed for local rice production and allow a longer fallowperiod for the managed rubber-fallow. A major cost isthat local food self-sufficiency would be sacrificed.

Our assessment of the dynamics of rubber andrice in Kalimantan differs significantly from that ofDove (1993), who sees rubber as entirely comple-mentary to dry-rice cultivation. While we agree thatthese crops are compatible in the household economy,as cash from rubber can effectively substitute for lostrice production, the ecological differences betweendry-rice and rubber have major implications for land-scape dynamics. Because the fallow length for dry-rice (8–20 years across Kalimantan) is much shorterthan the lifetime of a rubber garden (30–40 years), thetwo land-uses can not substitute for one another in thelandscape.

Elsewhere in the tropics, the expansion of treecrops has resulted in adjustments to the distributionand turnover of other land-use types in the agroecosys-tem. In Nigeria, increasing the total area under cul-tivation was the initial response to a rapid expansionof tree crops grown for cash. Eventually, the fallowperiod was reduced along with the area devoted tofood crops (Osunade 1991). Within 30 years, localfood production was inadequate to meet demand. Sim-ilarly, in Sumatra, Indonesia, the expansion of rub-ber came partly at the expense of remaining primaryforests, but it also reduced the extent of upland dry-rice (Mary and Michon 1987). In contrast, in tropicalChina, rather than reducing the land allocated to riceproduction, rubber displaced other agroforestry sys-tems (Saint Pierre 1991).

Landscape patterns associated with slash-and-burnworld-wide

Although the causes of deforestation and trajecto-ries of regrowth differ among tropical regions, com-paring their landscape dynamics is informative. Wecompared our data with contemporaneous data fromsatellite-image based studies of slash-and-burn sys-tems in Africa and Amazonia (Skole et al. 1994;Moran et al. 1994; Chatelain et al. 1996). We focusedon land that had been cleared from primary forest andwas currently under food crops (or bare), tree crops,pasture, or secondary forest. These categories corre-sponded to current rice fields, rubber or fruit gardens,(nothing comparable to pasture) and fallows in ourstudy, which we defined collectively as managed land.

A broad pattern of temporal change in land-useallocation was evident since the beginning of defor-estation. A higher proportion of land was in foodcrops, or bare, in areas more recently opened upto human settlement (Figure 7). The proportion ofmanaged land in secondary forest seemed to increaseover time, approaching within 25 years the proportionfound in a rainforest landscape dominated by humansfor over 200 years (this study).

Although the proportion of secondary forest wassimilar between landscapes with 25 and 200 yearsof deforestation, secondary forest in Northeast Brazilwas dominated by younger vegetation (> 80% of sec-ondary forest consisted of trees< 10 years old; Moranet al. 1994). In Kembera, assuming diameter growthrates of 1–2 cm per year, only 20–52% of the areain secondary forest was< 10 years old (Figure 4a).The difference in forest age-structure may be due toa longer fallow rotation in West Kalimantan or tothe sporadic course of land development in NortheastBrazil where periods of rapid clearing have been fol-lowed by periods of abandonment.

Conclusion

In the area near GPNP, shifting cultivation resultsin less deforestation than industrial land-use such astimber extraction and oil-palm plantations, especiallywhen we consider that logged forest is often convert-ed to other uses. Though rubber cultivation appearsto be the proximate cause of deforestation, politicaland economic insecurity are the ultimate causes. Rub-ber has profoundly affected the spatial pattern of thelandscape, initially reflecting trade-offs between workand travel time. The increasing predominance of rub-ber will ultimately determine the dynamics of dry-ricecultivation, once the exclusive factor defining the land-scape.

Contrary to what happens in areas where forest iscleared for permanent agriculture or pasture develop-ment, land-use intensification and the development ofa cash-dependent economy should result in a forest-ed landscape in parts of West Kalimantan current-ly dominated by shifting cultivation. The managed-rubber fallow would be longer, resulting in biggertrees across the landscape. Despite potential increas-es in forest stature, the diversity of these forests woulddecline if rubber replaces dry-rice fallows (Lawrence1996; Lawrence and Mogea 1996). Thus, while rub-ber would not change the grain of the landscape

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Figure 7. The proportion of deforested land in use or in succession in three regions of the moist tropics. Categories for the three satelliteimage-based studies (Southwest Ivory Coast [SIC], North Brazil [NB], and West Brazil [WB]) were similar, including a category for open orcropped land and one to many categories for secondary forest. In addition, tree crops were distinguished in SIC, and heavily degraded primaryforest was included in the secondary forest number presented here. Pastures were identified in NB but not in WB, thus part of the WB landscapein crop/bare may actually be in pasture.

under shifting cultivation, at the patch level, com-plexity would be lost. These changes in the structureand dynamics of the landscape may affect the persis-tence of primary forest species whose original habitatis increasingly threatened. Further research is neces-sary on how processes of forest regeneration are con-strained by changes in the managed landscape.

Acknowledgments

Funding for this research was provided by a grant fromthe Conservation, Food, and Health Foundation, Incor-porated (DCL). Grants from the United States Agencyfor International Development PSTC Program (DRPand ML), The Duke University Chapter of the Sig-ma Xi, The Center for International Studies at DukeUniversity, The Nature Conservancy, and The GardenClub of America/World Wildlife Fund (DCL) provid-ed additional support for the final stages of the project.The research would not have been possible without thesponsorship of the Center for Research and Develop-ment in Biology of the Indonesian Institute of Sciences(LIPI) in Indonesia and The Peabody Museum at Har-vard University in the United States. We owe a great

debt to the people of Kembera for their hospitality andassistance. D. Higdon and A. Ruetters provided statis-tical assistance. We also thank C. Cannon, L. Curranand C. Webb for support in the field and discussion.Comments by P. Kleinman, W. Schlesinger, J. Clark,and two reviewers improved the manuscript.

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