Using Geographic Information Systems to AssessPossibilities of Expanding Traditional Agroforestry inSlash-and-Burn Zones in Madagascar

Author: Nambena, Simon Michel

Source: Mountain Research and Development, 23(4) : 329-333

Published By: International Mountain Society

URL: https://doi.org/10.1659/0276-4741(2003)023[0329:UGISTA]2.0.CO;2

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The need for more sustainablefarming options

Madagascar has many highly diversifiedecological features: humid forests from thenorth to the south on the eastern side,xerophytic bushes in the extreme south,and dense dry forests on the western side(Figure 1). In the east, where rainfall canbe as high as 2500–3500 mm per year,slash-and-burn cultivation (tavy) domi-nates the agricultural landscape. Ecologi-cal and socioeconomic data were obtainedby the Terre Tany/BEMA (Bilan écolo-gique de la culture sur brûlis à Madagas-car) project—concerned with ecologicalevaluation of tavy in Madagascar andfinanced by the Swiss National ScienceFoundation—between 1994 and 2001,within a relatively limited zone. This zonecan be considered representative of east-ern Madagascar, where tavy is the mainagricultural activity among peasants. Thestudy site is located in the rural communeof Beforona, 160 km east of the capital.

The region is dominated by fallow,which constitutes a transition betweendegraded pseudosteppe vegetation in theeast and dense humid forest in the west.The altitude varies between 350–750 m,and the topography is highly uneven.There are very narrow V-shaped valleyswith steep slopes often greater than 60%.

Expanding tanimbolyTavy is the main ecological problem in theregion. Every farmer interviewed practices

tavy around the Vohidrazana Forest (a for-est near the study site). In addition, giventhe high rate of population growth, thefrequency of fallow cuttings has greatlyincreased. Before the 1970s, the averageperiod of fallow was between 15 and 20years. A study of vegetation dynamics inBeforona by Pfund et al (Projet Terre-Tany/BEMA 1997) revealed that the dura-tion of the fallow period lasts between 5and 6 years in new fallow zones, 4 years atolder exploited sites, and between 3 and 5years on the degraded soils, where theplots are highly subdivided. This phenom-enon was confirmed in an analysis byBrand et al (Projet Terre-Tany/BEMA1997), which shows that the deforestationprocess increased from 21.2 hectares/year(1957–1967) to 39.3 hectares/year (1967–1987), 46.5 hectares/year (1987–1994),and finally 51 hectares/year between 1994and 1997.

The agricultural labor involved withtavy absorbs most of the farmers’ agricul-tural calendar and can take up to 200 daysannually for each household. Althoughslash-and-burn agriculture is considered anonsustainable system, the same farmershave other more sustainable options attheir disposal, such as irrigated rice cul-ture and perennial cultures. The latter areoften found in the narrow valleys and con-sist of traditional agroforestry systems orfruit-tree gardens known locally as tanim-boly, where farmers produce coffee,banana, and other fruit. These productsare harvested during the year and are the

Using Geographic Information Systems to AssessPossibilities of Expanding Traditional Agroforestry in Slash-and-Burn Zones in Madagascar

Simon Michel Nambena

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Mountain Research and Development Vol 23 No 4 Nov 2003: 329–333

Beforona is a mountainous region in east-ern Madagascar, where slash-and-burn culti-vation (tavy) has been practiced for severalgenerations to produce rice, the staple foodof the Malagasy people. This system of cul-tivation has long been unsustainable (defor-estation, erosion, loss of soil fertility, etc).Other types of cultivation considered moresustainable were inventoried in a study, par-ticularly the irrigated rice field and tradition-al agroforestry system known as tanimbolyfound in the valleys. On the basis ofresearch results, data were incorporatedinto a Geographic Information System (GIS)to elaborate descriptive models using differ-ent parameters related to this farming sys-

tem. Spatial distribution of tanimboly showsthat more than 90% is concentrated alongsmall streams, in concave areas, and not onslopes and hillsides. Tanimboly becomesscarcer as the distance from the forestedge approaches 2 km, and surface areasare drastically reduced in proportion to dis-tance from roads. GIS and regression mod-els made it possible to identify potentialareas for tanimboly. Relations between thevarious parameters were calculated usinglogistic regression functions to predictoccurrence of the tanimboly phenomenon innonsampled zones. It appears that farmingstrategies are particularly influenced byinfrastructure.

FIGURE 1 The 4 agroecological regions inMadagascar, with location of the study area(Beforona). (Source: Bied-Charreton et al1981, in Projet Terre-Tany/BEMA 1997)

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Simon Michel Nambena

Mountain Research and Development Vol 23 No 4 Nov 2003

330

principal source of income for farmers,providing up to 40% of their total yearlyincomes (Moor, in Projet Terre-Tany/BEMA 1998).

In November 2002, the Malagasy gov-ernment implemented a law stipulatingthat any farmer who sets fire after cuttingtrees can be sent to prison for up to 5years; nevertheless, the Ministry of Agri-culture never proposed alternatives totavy. For this reason, some solutions areproposed here, including expansion oforchards on the basis of farmers’ know-how regarding available resources.

Using GIS to assess the potentialfor expansion of orchardsFor many centuries, slash-and-burn sys-tems have coexisted with different nation-al and international policies and strategiescharacterized by repression. Yet, it wasalways impossible to apply laws, given the

tolerance threshold allowed by the author-ities and the institutions concerned.Because the law has now been reinforcedand is being applied, we hypothesize thatthe orchards can be expanded in the longterm. Based on their empirical traditionalknowledge, farmers manage their fields inaccordance with ecological parameters,resource quality, and existing socioeco-nomic conditions.

Different modeling methods wereundertaken with version 7.2.1 of NTArcinfo. During the first phase, a DigitalElevation Model including rivers from1:50,000 maps was established. Next, thederived products (slope, exposition, etc)were calculated. The second phase ofmodeling consisted of overlaying the landuse map compiled by Brand and Randri-amboavonjy (Projet Terre-Tany/BEMA1997), particularly with tanimboly plots.Finally, these blocs were analyzed using 6geomorphological and socioeconomicparameters, to explain the spatial distribu-tion of these plots (Figure 4):

• Slope: Because of the abundance ofsteep slopes in the region, cultivation isindependent of slope values. The maxi-mum slope value where fields arefound is about 30%. When the slopesare greater than 125%, the orchardsare replaced by other types of cultiva-tion such as tavy, second-year cultiva-tion of ginger or cassava, or the landmay even be left fallow.

• Relief form: The concave parts of theland are highly prized by farmers fororchards (Figure 3). There are manyreasons for the choice of such sites.They present a relatively humid micro-climate, compared with rectilinear orconvex relief forms. Nutrients aredeposited in these zones, and soil ismore fertile, which is a necessary condi-tion for initial installation. Moreover,convex areas are prone to erosion andare also directly exposed to wind, whichmakes them relatively dry.

• Hillside exposures: Flat exposure, corre-sponding to 0% slope, is greatly pre-ferred for the installation of agro-forestry systems. However, the geomor-phology offers very limited areas of thistype. Currently 38% of flat land is used

FIGURE 2 Multiple crops aregrown in orchards, in asustainable form of land usecalled tanimboly. Orchardsprovide food for householdconsumption and are also asource of cash crops (ie,regular income). (Photo byauthor)

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for tanimboly. Orchard installation onother topographic exposures is donerather more at random. Orchards arefirst installed on a flat surface and thenexpanded according to suitable mor-phology (Figures 2 and 3).

• Distance from a forest corridor: The dis-tance from a forest corridor is an indi-cator of the intensity of the practice. Adistance of 2 km from the forest edge isthe point at which species compositionand orchard surface areas change dras-tically. In addition, the relative distribu-tion shows that the other types of culti-vation, especially tavy, predominatenear the forests.

• Distance from a road: The study area islocated along the national road, withthe farthest point about 3 km from theroad. This relatively small distance indi-cates that orchard installation dependson the presence of a permanent road.Large orchards are concentrated alongthe roads (0–500 m away). The areasdecrease with increasing distance froma main road or railway: if the distance isgreater than 1.5 km, the size oforchards gradually diminishes.

• Distance from a village: Because farmersprefer to install their orchards near

their houses, the most ancient planta-tions are concentrated around the vil-lages. After these preferred sites areoccupied, new installations appearalong the rivers. A regression modelshowed that proximity from rivers androads was the most significant indica-tor, whereas slope values and topogra-phy do not have significant impact onorchard distribution.

The modeling thus also took accountof socioeconomic parameters, demonstrat-ing that this model can analyze farmers’strategies for installing orchards. However,the model does not show the completeecological potential of land suitable foragroforestry.

Without considering forest distribu-tion, fallow and annual cultivation are ran-domly distributed according to the qualityof the site, although it can be observedhere that the quality of the site is notinvolved. Of the 572 hectares of goodsites, only 15% are occupied by orchards,whereas the remaining surfaces are leftfallow or used to grow annual crops(67%). However, it should be noted thatrice fields (9%) also compete for goodsites. Twenty-two per cent of the orchards

FIGURE 3 Vacant sites forpotential new orchards areplentiful on fallow land andcould be used to expandtanimboly. Orchards are usuallyconcentrated in valleys, butrecent plantations have alsomade use of favorableconditions on concave terrainat higher altitudes. (Photo byauthor)

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Simon Michel Nambena

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are installed on “bad quality sites.” Thereare several reasons for this: sites belong-ing to farmers who have no choice ininstalling their plots; sites that are not asbad as they may appear, because someparameters were not included in the mod-eling (land tenure or cultural problems);and sites where some important parame-ters were not considered (pedology, fallowage, commercialization). The land usetypes and corresponding percentages ofarea suitable for agroforestry are shown inTable 1.

Making agroforestry attractive andcost efficient

Constraints on effective commercializationUntil now commercialization of orchardcrops has been limited to coffee andbananas. Sugarcane is locally transformedto rum, and other fruits generally rot onthe site. Resources are underexploitedbecause of the lack of options for com-mercialization in the region. Farmershave developed the following alternativestrategies:

• Because an orchard produces fruitonly 3 years after it is planted, farmersprefer to grow annual crops (rice, gin-ger, cassava, etc) to boost theirincome.

• Given the need for income, good landis used for annual crops.

• Agricultural techniques remain tradi-tional and cannot satisfy the qualityand quantity requirements of the mar-ket.

• In some cases, land-tenure systems donot allow the practice of perennial cul-tivation because land is usually linkedto lineage rather than individual own-ership.

Suggested actionMotivating peasants to reduce slash-and-burn agriculture, while simultaneouslyinstalling new orchards or expanding oth-ers, will mean taking action in the follow-ing areas:

• Promoting new and more efficient agricul-tural techniques: Although this zone ispart of a region that exports Malagasy

Infrastructure

Perennial cultures

Suitability for agroforestry (tanimboly)

VillageNational road 2Railway

Rice fieldsNatural forestReforested areaExisting agroforestry systems

Best sitesSites for potential expansionUnsuitable sites Ampamelona

Ambodiaviavy

Ambohimarina

Bemanasy

Ambavaniasy

BEFORONA

Tanambao

Vakampotsy

Fierenana

Marovoalayo

Marolafa

620617.5 622.5 625

795792.5

2.5 Kilometers

N

FIGURE 4 Digital terrain model resulting from the study ofgeomorphological and socioeconomic conditions for the potentialexpansion of agroforestry. (Map by author)

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crops, it has been left to use traditionaltechniques, resulting in the persistenceof slash-and-burn agriculture.

• Solving land-tenure problems: Land regis-tered in a cadastre with a title is cur-rently very rare. All the land left fallowat present is tied to lineage; onlyorchards, reforested land, and ricefields are owned by individuals. Landregistration is so expensive that peas-ants prefer to keep traditional bound-aries, where all individuals linked bylineage can use fields after negotiation.

• Improving infrastructure: The rugged

topography of the whole region inhibitsdevelopment, especially regardingtransport. Although both the nationalroad and the railroad pass through thiszone, in some communes even smalltrails are lacking. Sometimes producershave to walk for an entire day to selltheir crops.

• Organizing a favorable trading system:Because of lack of information, farmersare at the mercy of middlemen. In fact,they do not know the selling prices oftheir products; the middlemen setprices to their own advantage.

Land use Suitability for agroforestry Area (hectares)% of total

suitability classSubtotal

(hectares)

Natural forest Unsuitable sites 487.2 20680.5(14%)

Potential for expansion 168.3 9

Best sites 25.0 4

Fallow and annual crops

Unsuitable sites 1856.8 763655.5

(75%)Potential for expansion 1413.7 77

Best sites 385.0 67

Reforestation Unsuitable sites 13.8 171.7(1%)

Potential for expansion 35.6 2

Best sites 22.2 4

Rice fields Unsuitable sites 16.5 1129.1

(3%)Potential for expansion 58.8 3

Best sites 53.8 9

Agroforestry Unsuitable sites 68.4 3317.1

(7%)Potential for expansion 162.5 9

Best sites 86.3 15

Villages Unsuitable sites 0.1 01.9(0%)

Potential for expansion 1.2 0

Best sites 0.6 0

Total Unsuitable sites 2442.9 1004855.7(100%)

Potential for expansion 1840.1 100

Best sites 572.8 100

TABLE 1 Land use types and percentage of area suitable for agroforestry (tanimboly).

FURTHER READING

Chou YH. 1997. Exploring SpatialAnalysis in Geographic Information Sys-tems. Santa Fe, NM: OnWord Press.Projet Terre-Tany/BEMA, editor. 1997.Un système agro-écologique dominépar le tavy: La région de Beforona,falaise Est de Madagascar. CahiersTerre-Tany 6. Antananarivo, Madagas-car: Projet Terre-Tany/BEMA [Bilanécologique des cultures sur brûlis àMadagascar] and FOFIFA [CentreNational de la Recherche Appliquée auDéveloppement Rural]; Berne, Switzer-land: Centre for Development and Envi-ronment.Projet Terre-Tany/BEMA, editor. 1998.Les stratégies endogènes et la gestiondes ressources naturelles dans larégion de Beforona. Les résultats desrecherches pluridisciplinaires de laphase 1995–1998. Cahiers Terre-Tany8. Antananarivo, Madagascar: ProjetTerre-Tany/BEMA [Bilan écologique descultures sur brûlis à Madagascar] andFOFIFA [Centre National de laRecherche Appliquée au Développe-ment Rural]; Berne, Switzerland: Cen-tre for Development and Environment.

ACKNOWLEDGMENTS

This study is based partly on a PhDthesis on regionalization of naturalresource management strategies inthe middle and eastern parts of Mada-gascar. It was financed by BEMA (Bilanécologique des cultures sur brûlis àMadagascar). I wish to express my sin-cere thanks to my wife Jutta, whoadvised me on GIS modeling and sup-plied supplementary information aboutfarmers’ strategies. I also wish tothank Dr Rakouth for her translation.

AUTHOR

Simon M. NambenaDERAD (Diagnostic environnemental etrecherches appliquées pour ledéveloppement en milieu rural), POBox 60115, Antananarivo 101, Mada-gascar.nambena@wanadoo.mg

Simon Nambena is currentlyengaged in research for a PhD thesison natural resource management atthe University of Antananarivo; he isfocusing on the extrapolation of locallyobtained research results on alterna-tives to slash-and-burn agriculture tothe regional level. He is also working asmanager and GIS and remote sensingspecialist for DERAD, a consultingagency for rural research and develop-ment in Madagascar.

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