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Human and Environmental Factors Affect Patterns of Crop Diversity in anEthiopian Highland AgroecosystemLeah H. Samberga; Carol Shennana; Erika S. Zavaletaa

a University of California, Santa Cruz

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To cite this Article Samberg, Leah H. , Shennan, Carol and Zavaleta, Erika S.(2010) 'Human and Environmental FactorsAffect Patterns of Crop Diversity in an Ethiopian Highland Agroecosystem', The Professional Geographer,, Firstpublished on: 01 June 2010 (iFirst)To link to this Article: DOI: 10.1080/00330124.2010.483641URL: http://dx.doi.org/10.1080/00330124.2010.483641

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Human and Environmental Factors Affect Patterns of Crop

Diversity in an Ethiopian Highland Agroecosystem∗

Leah H. Samberg, Carol Shennan, and Erika S. ZavaletaUniversity of California, Santa Cruz

The Ethiopian highlands are a center of diversity for numerous globally important crops. Heterogeneouslandscapes, traditional agricultural practices, and inaccessibility have created and maintained diversesubsistence agroecosystems. We surveyed sixty-three farms in twelve communities of the Gamo highlandsand found high levels of on-farm diversity of crop species and varieties. The extent and nature of thisdiversity are related to both ecological factors, namely elevation, and anthropogenic factors such as land-usehistory, accessibility to markets and extension, and strength and scale of farmer exchange networks. Thesehuman landscape features have the potential to both enhance and mediate effects of elevation and otherenvironmental factors on crop diversity. The interaction of environmental and anthropogenic forces on thediversity of crops grown by farmers affects the strategies farmers employ to adapt their farming to changingconditions. Key Words: agricultural biodiversity, agroecology, Ethiopia, farmer seed systems, landraces,vulnerability.

Las montanas etıopes son un centro de diversidad de numerosas plantas de cultivo globalmente importantes.Los paisajes heterogeneos, practicas agrıcolas tradicionales e inaccesibilidad han creado y mantenido diver-sos agroecosistemas de subsistencia. Nosotros estudiamos sesenta y tres granjas en doce comunidades de lasmontanas de Gamo y hallamos altos grados de diversidad de especies y variedades cultivadas al nivel de granja.La extension y naturaleza de esta diversidad se relaciona tanto con factores ecologicos, o sea la elevacion, comocon factores antropogenicos, tales como historia del uso del suelo, accesibilidad a los mercados y extension,y fortaleza y escala de las redes de intercambio del cultivador. Estos rasgos humanos del paisaje tienen lacapacidad potencial de fortalecer e intervenir los efectos de la elevacion y otros factores ambientales sobrela diversidad de las cosechas. La interaccion de fuerzas ambientales y antropogenicas sobre la diversidadde lo que plantan los granjeros afecta las estrategias que estos emplean para adaptar sus cultivos a condi-ciones cambiantes. Palabras clave: biodiversidad agrıcola, agroecologıa, Etiopıa, sistemas de semillasdel cultivador, plantas cultivadas autoctonas, vulnerabilidad.

A current focus of research throughout theenvironmental sciences lies in examining

the role of biodiversity in determining thevulnerability or resilience of an ecosystem to

∗The Christensen Fund provided the inspiration and funding for this research. The field team included Abera Ogato, Getachew Eshete, TarekegnShado, and Tizazu Gebre. Dr. Sebsebe Demissew and Dr. Zerihun Woldu, from the University of Addis Ababa, provided advice and guidance.We also thank Arba Minch University, zonal and local governments, and numerous agricultural offices for their help and support of this work.

changing conditions. The majority of conser-vation research and practice is concerned withdiversity in natural systems, but there is anincreasing body of work seeking to quantify

The Professional Geographer, 62(3) 2010, pages 1–14 C© Copyright 2010 by Association of American Geographers.Initial submission, November 2008; revised submission, August 2009; final acceptance, October 2009.

Published by Taylor & Francis Group, LLC.

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2 Volume 62, Number 3, August 2010

and assess biodiversity in the agricultural land-scapes that cover much of the earth’s sur-face and are vulnerable to the same forces ofland-use change and environmental change. Inmany places in the world these remain in theform of traditional subsistence agricultural en-vironments in which humans have, over thetime-scale of millennia, helped to define thelandscape, as well as the distribution of species,populations, and genes. Within these agricul-tural ecosystems lies a host of biodiversity,which not only contributes to the richnessof life on the planet, but also provides forthe livelihoods of farmers and the genetic ba-sis for global food production. Biodiversity inagroecosystems has the potential to increaseproductivity, regulate nutrient cycling andmicroclimatic conditions, reduce temporalvariability, and maintain resistance and re-silience in the face of socioeconomic or envi-ronmental change (Tsegaye 1997; Altieri 1999;Shennan 2008).

Landraces and Farmer Management

of Genetic Diversity

Crop diversity is concentrated in a number ofcenters of origin and diversification, where evo-lution of crop species has occurred throughmillennia of interacting natural and humanselection pressures, heterogeneous environ-ments, isolation, migration, and farmer ex-change (Harlan 1975). The resulting landracesare genetically diverse and adaptable, allowingfarmers to cope with heterogeneous environ-ments (Bellon 1996).

Although in many places traditional andmodern varieties coexist (Brush and Meng1998; Zimmerer 2003), land-use intensifica-tion, increased market integration, and accessto high-yielding varieties are generally asso-ciated with the loss of crop genetic diversity(Bellon 1996) and decreases in the number offarmers growing landraces and the area of land-race cultivation on farms (Teklu and Hammer2006). These trends make crop populationsincreasingly vulnerable to environmental anddemographic stochasticity.

Although crop varieties are often seen asbeing adapted to specific microclimates, how-ever, seed flow between varieties and farms canlead to broader adaptability, and varietal rangeshave been seen to be determined by seed flow

rather than agroecological conditions (Zim-merer 2003). There is increasing interest in un-derstanding the movement of seeds and otherplanting materials between farmers in tradi-tional agroecosystem worldwide (Almekinders,Louwaars, and de Bruijn 1994). Although eachsystem has unique features, there are a num-ber of common findings, namely that informalsocial networks play a large role in seed flow,and that in even the most isolated regions thereis some amount of farmer-mediated gene flowover long distances and across heterogeneousagroecological zones (Zimmerer 2003; Sebokaand van Hintun 2006; Badstue et al. 2007).

Agricultural Biodiversity in Southern

Ethiopia

The African Rift Valley contains some of theplanet’s most ancient agricultural systems, andthe highlands rising out of the valley in south-ern Ethiopia support one of the densest ruralpopulations in Africa. These mountains are acenter of genetic diversity for globally impor-tant crops such as wheat, barley, and sorghum,and a center of origin for crops such as khat,coffee, enset, Ethiopian kale, Oromo potato,and tef (Teklu and Hammer 2006). Previousresearchers in Ethiopia have noted that per-sistence of diverse landraces most often occursin regions that are economically remote, havesmall-scale land management, are in hetero-geneous and hilly environments, and in whichpeople have a cultural preference for diversity(Tunstall, Teshome, and Torrance 2001). All ofthese factors accurately describe the Ethiopianhighlands, suggesting high potential for themaintenance of crop diversity.

In 2007, an interdisciplinary team ofresearchers carried out an agroecologicalassessment of the Gamo highland region ofsouthern Ethiopia to investigate its potentialfor designation as a UN Food and AgricultureOrganization Globally Important AgriculturalHeritage System. A focal point of our assess-ment was an investigation of the extent anddistribution of agricultural biodiversity acrossthe region, to better identify threats and deter-mine appropriate measures for conservation.Due to the region’s high species and geneticdiversity, steep altitudinal gradients, and longhistory of cultivation, we hypothesized thatboth the extent and distribution of inter- and


Patterns of Crop Diversity in an Ethiopian Highland Agroecosystem 3

intraspecific diversity and the ability of farmersto maintain that biodiversity in the face ofchanging conditions would be affected by bothenvironmental gradients and anthropogenicpatterns of land use, accessibility, and farmerexchange networks. We surveyed species andfarmer-identified variety diversity of crops atfarm and community scales in communitiesdiffering in elevation and accessibility toroads. Our goal was to better understandthe ways in which human and environmentalprocesses affect agricultural biodiversity in thistraditional agroecosystem, as well as the forcesthat might threaten that biodiversity.

Study Area and Methods

The Gamo HighlandsThe Gamo-Gofa Zone, in the SouthernNations, Nationalities, and Peoples Region(SNNPR) of Ethiopia, lies on the westernshores of the Rift Valley lakes Chamo andAbaya. Part of the Gughe mountain range, theGamo highlands run southwest to northeast,are roughly 100 km long and 30 km wide (06◦

02-27′N, 37◦10-37′E), and reach above 4,000m. Native vegetation includes mixed deciduouswoodlands, dry evergreen montane forest, andalpine grasslands. Annual rainfall is bimodal,and mean annual temperatures range from10◦C to 25◦C (Ministry of Agriculture, Fed-eral Democratic Republic of Ethiopia [MoA]2000).

These densely populated highlands are hometo nearly 1 million people (Federal Demo-cratic Republic of Ethiopia [FDRE] 2008).Two vehicle-accessible dirt roads cross thesouthern and northern reaches, and the cen-tral areas have little to no road access. Theseroads connect the highlands to the commercialcenters of Arba Minch and Wolaita-Sodo, inthe valley, and from there to the capital in Ad-dis Ababa, 500 km to the northeast. These low-land zones are home to commercial agriculturalenterprises, especially for cotton and banana,and are incorporated into national commoditymarkets.

Conversely, agricultural production in theGamo highlands is almost entirely composedof subsistence farms of generally less than1 hectare. High elevations, high populationdensities, rugged topography, and lack ofall-weather roads have largely precluded the

establishment of commercial or large-scaleagriculture. The traditional Gamo homestead(Figure 1) is ringed by the household’s ensetplantation, a mixture of tree, vegetable, androot crops and agroforestry trees. Beyond thisring are crop fields, parts of which are left fallowand used as private grazing land. The ridges andplateaus of the highland chain are maintained asgrasslands, and locally managed as communalpastures.

Enset (Ensete ventricosum), the highlands’ pri-mary staple food, is a perennial crop in theMusaceae, or banana family. Wild enset is foundthroughout Asia and Africa, but domesticationis unique to Ethiopia, where it is a staple for7 to 10 million people (Tsegaye and Struik2002). Areas of enset cultivation range from1,200 m to more than 3,000 m, and farmers cul-tivate dozens of genetically distinct landraces(Negash and Niehof 2004).

Community and Farm SurveysHouseholds in the Gamo are organized into ke-beles, administrative units of 1,000 to 5,000 peo-ple (communities). Twelve communities wereselected from various elevations and pointsalong the north–south axis of the Gamo high-lands (Table 1; Figure 2). Communities wereidentified as (1) high (> 2,500 m) or low(< 2,500 m); (2) in the northern or southernhalves of the range; and (3) accessible, definedas lying on or near one of the region’s two all-season roads, with regular or occasional publictransport, or remote, having no direct access topublic transport and being inaccessible by ve-hicle for some or all of the year. In each com-munity, the research team held a focus groupdiscussion, and administered four to seven on-farm surveys, for a total of sixty-three farms.Focus groups were made up of eight to twelvemembers selected by the community chairman,and designed to include farmers of various ages,genders, and resource levels. Discussions ad-dressed natural resource management, culturaland social structures, community-wide crop di-versity, and perceived environmental or agri-cultural changes. Farms for household surveyswere selected to represent the geographicalrange of each community and to include bothfemale and male farmers. Surveys recordedintra- and interspecific diversity of all crop andtree species, as well as management practicesand livelihood strategies.



Figure 1 Farms in the Gamo are composed of several huts surrounded by enset, vegetables, rootcrops, and trees. Cereals such as barley are grown in plots outside the homestead.

Due to constraints of this preliminary studydesign, on-farm measurement of diversitywas limited to richness of farmer-identifiedspecies and varieties and did not include othermeasurements such as evenness. In addition,morphological and genetic analysis of crop va-rieties was not within the scope of this study.Identification of crop varieties was based solelyon the local naming system of farmers. The useof local names has often been used as a proxy for

genetic diversity, with significant limitations.Studies have shown that farmers’ variety namescorrelate positively but weakly with genetic andmorphological differentiation (van Leur andGebre 2003; Negash and Niehof 2004) and canbe a useful indicator of crop varietal diversity(Nuijten and Almekinders 2008). Subsequentwork in the region, including genetic analysisof crop varieties, will address many of theselimitations.

Table 1 Communities surveyed in the course of an agroecological assessment of the Gamo highlands

No. Community Accessibility North/South Average elevation (m)

1 Geta Accessible South 1,9772 Bola Hanika Remote South 1,9963 Belta Toleta Accessible South 2,6194 Kecha Kashaso Remote South 2,9815 Gughe Gatse Remote South 2,9736 Zigiti Merche Accessible South 2,2997 Weyza Tuka Remote North 2,2208 Gena Kare Remote North 3,0129 Bele Remote North 2,305

10 Boya Tupa Accessible North 2,66111 Ezo Tula Accessible North 2,84212 Dega Zonga Accessible North 2,419



Figure 2 (A) Communities and farms surveyed in the course of an agroecological assessment of theGamo highlands. Each dot represents a farm surveyed; clusters indicate community groupings. (B) Mapof Ethiopia, location of Gamo highlands: 06◦ 02-27’N and 37◦10-37’E.

Crop species and variety diversity were ana-lyzed in relation to elevation and accessibility atboth farm and community levels through lin-ear regressions, and composition of species andvariety assemblages was analyzed through mul-tivariate principle component analysis (PCA),analysis of variance, and cluster analysis usingJMP statistical software (JMP, Version 8).

Results

Crop Species DiversityOver the course of the study, fifty-fourcrop species were recorded (Table 2). Crop

assemblages vary greatly between farms andcommunities and are highly dependent on el-evation. Lowland crops, such as coffee, sugarcane, cassava, sweet potato, and yam, extendto elevations of 2400 m or more, while mid-altitude crops such as taro, squash, wheat, pep-pers, and beans are present in all but thehighest communities (>2800 m), where en-set, barley, cabbage, potato, and Oromo potato(Plechtranthus edulis) dominate the system.Within these broad zones, farmers also makecrop diversity decisions based on slope, soiltype, and other microclimatic factors. A num-ber of wild species are also tolerated or en-couraged on fallow fields and intercropped with



Table 2 List of crop species found on Gamo farms

Crop Common name Crop Common name

Aframomum korerima Ethiopian cardamom Lactuca sativa LettuceAllium sativam Garlic Lens culinaris LentilAllium cepa Onion Linum spp. LinseedArrisaema spp. Koltso Malus sylvestris AppleArtemesia spp. Sage Mangifera Indica MangoAvena sativa Oat Manihot esculenta CassavaBeta vulgaris Beetroot Musa paradisica BananaBrassica carinata Ethiopian kale Nicotana tabacum TobaccoBrassica oleracea Cabbage Ocimum basilicum BasilCairica papaya Papaya Passiflora edulis Passion fruitCapsicum annum Pepper Persea americana AvocadoCapsicum frutscens Pepper Phaseolus vulgaris Common beanCitrus fruitiscens Orange Physalis peruviana Ground cherryCitrus lemon Lemon Pisum sativum PeaCoccinia avyssinica Ushushe Plechtranthus edulis Oromo potatoCoffea arabica Coffee Prunus communis PlumColocasia esculenta Taro Rhamnus prinoides GeshoCorriandrum sativum Coriander Ricinus communis Castor beanCucurbita pepo Squash Ruta chalapensis RueDaucus carota Carrot Saccharum spp. Sugar caneDiascorea spp Yam Solanum tuberosum PotatoEleusine coracana Finger millet Sorghum bicolor SorghumEnsete ventricosum Enset Thymus patala ThymeEragrostis teff Teff Triticum aestivum WheatFoeniculum vulgare Fennel Vicia faba Faba beanHordeum vulgare Barley Zea mays MaizeIpomoea batatas Sweet potato Zingiber officinale Ginger

cultivated species. Farmers described numer-ous benefits of crop diversity, including nu-tritional benefits, uses for fiber, fodder, andconstruction, cultural uses, and agroecologicalbenefits.

Crop species diversity declines with increas-ing elevation at both farm and community lev-els. Communities at low and middle elevationscultivate up to forty-one crop species, averag-ing nineteen species per farm, whereas commu-nities at the highest elevations cultivate fewerthan twenty, averaging between nine and tenspecies per farm. Farmers are very deliberate intheir selection of crops, generally only plantingthose they feel will be most productive for theirelevation, soil type, and specific agroecologicalzone.

In addition, there is evidence to suggest thatthe elevation–diversity relationship is modifiedby the accessibility of farms and communitiesto other communities, regional markets, andextension services. Crop diversity in remotecommunities shows a stronger relationshipto elevation than does diversity in accessiblecommunities (Figure 3), indicating that factorsother than elevation play a larger role in

determining diversity in these more accessiblecommunities.

PCA of the identity of crop species at thefarm level shows that crop assemblages are de-termined both by elevation and by the locationof communities and their proximity to one an-other (Figure 4). The first principle componentis highly correlated with the elevation of thefarm (p < 0.0001), whereas the second princi-pal component differentiates between commu-nities in the northern and southern halves ofthe range (p < 0.0001).

Diversity of Crop VarietiesOver the course of the study, 139 named vari-eties of enset were recorded. Although, as notedearlier, this is not necessarily an accurate rep-resentation of genetic diversity, this figure re-flects intricate management of enset diversity.Between seventeen and sixty-six varieties werereported within each community, the highestat elevations of 2,500 to 2,800 m, with an av-erage of fifteen varieties per farm, and the low-est at elevations below 2,000 and over 3,000



Figure 3 Crop species diversity on farm shows(A) a strong relationship to elevation in remotecommunities (r2 = 0.53, p < 0.001), and (B) aless strong relationship in accessible communities(r2 = 0.08, p = 0.118).

m, with an average of six and seven varieties,respectively.

Farmers throughout the region were able toquickly identify and describe each variety byattributes such as size, leaf, stem, midrib color,maturation time, and food quantity and qual-ity. Farmers provide a number of explanationsfor maintenance of enset diversity. The firstis the multipurpose nature of enset; differentvarieties are considered to have different valuesfor a number of food types, shade and wind-break, fodder, fiber, construction material, andcultural purposes. Another reason given for on-farm enset diversity is the variation in matura-tion time (three to ten years), allowing farmersto evenly spread the availability of enset prod-ucts across years. Farmers also noted the es-thetic value of a diverse enset plantation as asign of a beautiful homestead.

Sixty-five named varieties of barley wererecorded, and average on-farm diversity of

named varieties increased with elevation at thecommunity scale (p = 0.027). In all cases, farm-ers described the importance of selecting barleyvarieties that are suitable for their specific eleva-tion and agroecological conditions and the roleof barley diversity in the maximization of pro-ductivity on fields of specific soil types, eleva-tion, moisture levels, and topography, as well asfor various food types and cultural uses. Farm-ers also reported growing numerous varietiesof other staple crops such as yam, taro, andOromo potato.

Although the number of named varieties ofmost crops is correlated with elevation, theidentity of varieties is largely dependent onproximity of farms and communities to eachother. A cluster analysis of enset variety namesat the community level shows that communi-ties tend to cluster with adjacent communi-ties, regardless of elevation, and the analysisclearly separates the six northernmost commu-nities from the six southernmost communities(Figure 5A). Similarly, cluster analysis showsthat similarity in named barley varieties at thecommunity level is associated with both geo-graphic proximity and elevation (Figure 5B).

The distribution of named varieties acrossthe region was similar in enset and barley. Fifty-six percent of barley varieties and 49 percent ofenset varieties were found in only one commu-nity, indicating community-level management,naming, and exchange of planting material; but11 percent of enset varieties and 9 percent ofbarley varieties were found in eight or more ofthe twelve communities, providing evidence forexchange of planting material and informationover longer distances.

Agricultural Extension and Seed ProvisionAlthough the Gamo highlands continue to bedominated by small-scale subsistence agricul-ture, government agricultural extension offices,located in each community, are working to pro-vide farmers with seed and inputs. These in-troductions significantly influence the richnessand assemblages of crops grown on many farmsand might move farms either toward intensi-fication of subsistence production or towardgreater market-oriented production.

More than two thirds of farmers surveyed re-ported trying out crops made available throughextension or nongovernmental organizations



Figure 4 Principal component analysis of crop species assemblages on surveyed farms. Colors signifynorth–south location, and H/L indicates high (> 2,500 m) or low (< 2,500 m) elevation. The first componentexplains 20.5 percent of the variation and correlates significantly with elevation (p < 0.0001). The secondcomponent explains 10.5 percent of the variation and correlates significantly with north–south location(p < 0.0001).

(NGOs). In low- and middle-elevation com-munities, these are primarily root crops suchas sweet potato and improved cereals such asmaize and teff. In the highlands, the most com-mon introductions are wheat, potatoes, andfruits and vegetables such as beets, carrots, ap-ples, and plums. The use of seed provided by ex-tension offices was more prevalent in the lowerstudy communities, where 71 percent (twentyof twenty-eight) of farmers surveyed reportedreceiving seed from extension, whereas in high-elevation communities, 38 percent (fourteenof thirty-seven) of farmers were using, or hadused, seed directly from extension offices.

The extent to which farmers adopt new cropsand varieties from extension offices has the po-tential to be affected by both farmers’ interestand by the ability of the extension to provideappropriate and timely inputs. In the first case,

many farmers described active distrust of ex-tension services, preferring their own knowl-edge and traditional crops. This perspective wasmost common in the highland communities,with several farmers commenting that “we al-ready know how to farm.” Sixty-five percent offarmers (54 percent of farmers in lower com-munities and 70 percent of farmers in highercommunities) reported explicitly negative ef-fects of seed packages, fertilizer packages, orboth received from extension services, citingeither declines in productivity or problems cre-ated by the inability to repay loans.

On the supply end, extension offices are of-ten unable to procure seeds for more than a fewfarmers in a community, even where greaterdemand exists. In addition, both farmers andextension officers note that improved seed andrelated inputs are prohibitively expensive for



Figure 5 Cluster analysis of named enset andbarley varieties by community. Communities areindicated as high or low, and colored by north–south location. (A) Enset varieties: The six north-ernmost and six southernmost communities grouptogether. (B) Barley varieties: Clusters reflect bothelevation and proximity of communities to oneanother.

the majority of Gamo farmers. The researchteam also observed a great deal of variability be-tween communities in the extent to which agri-cultural extension offices are staffed, funded,and engaged with farmers.

Population Growth and Shrinking FarmsThroughout focus groups and household in-terviews, farmers identified population growthas the most pressing threat to the agricul-tural system in the Gamo highlands. Elevenout of twelve focus groups, and farmers in alltwelve communities, explicitly made mentionof shrinking farm sizes, decreased fallow pe-riods, and declining grazing resources due toincreased population pressure.

The population of the SNNPR has grownat a rate of 2.9 percent since the 1994 cen-sus, with 48 percent of its current populationunder the age of fifteen (FDRE 2008). Pop-ulation growth in the Gamo highlands might

be significantly higher than this; changes incensus methodology and political delineationsmake such figures unreliable, but comparisonsof the 1994 and 2007 censuses indicate a popu-lation increase of as much as 25 percent acrossthe five Gamo districts represented in this sur-vey (FDRE 1996, 2008). Land redistributionefforts during the Derg regime in the 1980sbroke down traditional landholding arrange-ments and allocated plots of land to individualfamilies. Land tenure involves subdivision ofland between sons; thus the increasing popula-tion associated with decreases in mortality andpolitical barriers to land expansion have led toa rapid decrease in farm size from 2 hectares toless than 0.5 hectares per household, accordingto community officials.

Farmers report diverse effects of this in-creasingly limited availability of land, includingshortened or absent fallow periods, detrimentaleffects on crop productivity and soil health,reduced availability of grazing land, andabandonment of crops, such as sorghum, withlong growing seasons. Forty percent of farmersreported decreasing their livestock ownershipover the past twenty years due to shortages inpasture; 46 percent reported decreases in cropproductivity over that time due to continuouscultivation of fields, lack of manure, or both;and 20 percent reported abandoning specificcrops entirely due to land or manure shortage.

Discussion

The Gamo highlands are defined by diversefarms and steep gradients in elevation andassociated agroecological zones. As in naturalecosystems, elevation largely defines the rich-ness and composition of species assemblages,and human management of crop diversity hasthe potential to interact with the environmen-tal gradient in a number of ways. In one keyinteraction, land-use history and agriculturalextension services differ among elevationzones, further increasing the effect of elevationon cropping patterns. Conversely, communityconnectivity and the exchange of plantingmaterial and information between farmershave the potential to moderate the effects ofenvironmental gradients. These interactionscan affect the diversity available to farmers,and therefore the strategies used by farmers



to adapt the agroecosystem to changing condi-tions, including increasing population density.

Unpacking ElevationElevation clearly emerges as a key feature de-termining the diversity of crops and varieties onGamo farms. This elevation gradient includesa number of important features, both environ-mental and anthropogenic. Ecologically, eleva-tion is a proxy for a number of system-specificenvironmental variables, including tempera-ture and rainfall patterns (Carpenter 2005). Inthe Gamo highlands, higher elevations (aboveapproximately 2,500 m) are significantly coolerand moderately wetter than lower elevations(MoA 2000). In the majority of ecosystems, agreater diversity of species is able to thrive atlower elevations, and this drives much of the re-lationship between crop diversity and elevationseen in the Gamo.

In addition, elevation has long defined boththe agriculture and culture of the Gamo. Asdescribed by farmers, it is the highlands above2,500 m that have traditionally been cultivated,and have historically (as well as currently) beenthe most densely populated, whereas the lowerreaches of the study area have long been allo-cated for pastoral uses or secondary agriculturalfields. We observed that highland crops such asenset and barley are considered the most cul-turally important crops, and traditional institu-tions of governance and religion are centeredin highland areas. According to farmers andcommunity officials, the lower slopes of theregion have been intensively settled and cul-tivated much more recently, and much of thissettlement has been driven by government landredistribution programs.

Thus, elevation also represents land-usehistory, population density, and strength oftraditional social networks and cultural insti-tutions. These factors can affect the decisionof farmers to grow certain crops or varieties,the ability of farmers to access planting mate-rial and information, and the preferred sourcesof planting material, information, and otherinputs.

Relatedly, the role of government agricul-tural extension efforts is markedly different athigh and low elevations (Tunstall, Teshome,and Torrance 2001). Many of the crops pro-vided by extension offices are lowland crops

such as maize, teff, and sweet potato, which arewelcome additions to many farms in the low andmiddle altitudes, whereas the highland areas areoften not suitable for many improved crop vari-eties. Extension efforts in the highland regionsare more frequently focused on fruits and veg-etables grown to supplement farm production,rather than to replace staple crops.

The smaller farm sizes of the highlands arealso a barrier to the adoption of new cropsor varieties at higher elevations, where thereis little space for experimentation. In addition,the lack of traditional cropping practices andinstitutions in more recently cultivated lowerslopes might be associated with a greater will-ingness to adopt crops provided by extension,whereas in the highland areas many of the farm-ers surveyed were skeptical of extension ser-vices. These differences have the potential tofurther strengthen the environmental gradientsassociated with elevation in regard to crop di-versity and composition.

Farmer Exchange and Crop DiversityAs is seen in many studies of traditional sub-sistence agroecosystems, Gamo farmers’ use oftheir own saved seed is regularly supplementedby the exchange and purchase of planting mate-rial. Reasons given for seed acquisition includeexperimentation and replacement of unproduc-tive seed and seed lost to consumption, weather,or pests.

Although the majority of named enset andbarley varieties are found in only one commu-nity, several varieties of each crop are seen incommunities at differing elevations and signif-icant distances. Several studies examining thedistribution of genetic diversity in crop plantshave found different patterns of exchange at lo-cal versus regional scales (van Etten et al. 2008),and such a dichotomy is likely the case in thissystem as well. These findings largely supportthe findings of previous studies of the distri-bution of farmer-named varieties in Ethiopia,which have found that, although the majorityof named varieties are localized in distribution(Tamiru and Becker 2008), some widespreadvarieties are generally present (Tesfaye andLudders 2003), and most of the genetic vari-ation is found within crop populations ratherthan between them (Beyene, Botha, and My-burg 2006). These studies have found similarity



in varieties of sorghum (Seboka and van Hin-tun 2006), yams (Tamiru and Becker 2008), andenset (Tesfaye and Ludders 2003) in communi-ties at considerable distance from one another.These studies and others cite the movementof genetic material by farmers through formaland informal seed networks as a driving forcein determining these patterns.

The majority of crop varieties identified inthis study are found in only one community.This community scale is the venue for the ma-jority of social networks, and nearly all farm-ers surveyed described participation in workgroups, markets, and meetings with other farm-ers in their community. Farmers in the Gamoare very conscious of specific agroecologicalconditions, and surveyed farmers emphasizedthe importance of seeking out local seed thatwill be well adapted to their fields. In addition,given the nontransparent nature of seed prove-nance and quality, exchanges of planting mate-rial require considerable trust between parties(Badstue et al. 2007; McGuire 2008), furtherincreasing the appeal of local exchange. Thesefactors likely affect the propensity of varieties,and variety names, to be locally distributed.

Several surveyed farmers, however, de-scribed relationships and exchanges over dis-tance through family, long-distance travel tomarkets, and dissemination by extension agentsand NGOs. Farmers report traveling long dis-tances to reacquire varieties when lost, often ac-quiring planting material from higher or lowerfarms or communities. Effects of these transac-tions are seen in the presence of varieties foundin all or many communities, as well as the ten-dency of crop and varietal assemblages to bemore similar in communities in close proximity.

This study found that communities are morelikely to have named varieties of enset and bar-ley in common with nearby communities thanwith distant communities, regardless of eleva-tion. This is similar to findings by Tesfaye andLudders (2003), who found that, although ensetdiversity was related to elevation, shared ensetlandraces fell off with distance between farmsand communities. These patterns indicate thatnearby communities have both a shared lexiconfor naming varieties and a pattern of intercom-munity exchange of planting material.

This pattern is evident at the crop specieslevel also, as farmers within a community, andfarmers in nearby communities of similar ele-

vation, have more similar repertoires of cropsthan farmers in distant communities. We ob-served two main pathways for this clustering.First, as new crops are added to the system fromextension or NGO offices, they are dissemi-nated by farmers to friends and neighbors andthrough local markets. This was observed inthe cases of improved wheat and several potatovarieties, as well as fruits and vegetables. Sec-ond, if some farmers are able to maintain acrop or variety through a bad year, they arethen able to provide seed to other farmers whohave lost their own, most likely to farmers intheir own community or nearby communities.Farmers in those communities will continue togrow that crop or variety, although communi-ties elsewhere might have lost it entirely.

In communities where both the influx ofnew seed and seed exchange between farmersis more common, Gamo farmers with betteraccess to seed exchange networks can cultivatecrops and varieties across a broader range ofmicroclimates, be better able to replace cropsand varieties when lost, and cultivate more di-verse crop and varietal mixtures on farms. Thisincreased ability to add or replace seed likelyplays a role in the observed decreased correla-tion between elevation and crop diversity foundin the more accessible communities surveyed.

Diversity and Adaptability of CultivationStrategiesCrop diversity, landscape diversity, and diver-sity of agricultural strategies provide Gamofarmers with the potential to adapt their agroe-cosystem to changes in population density andenvironmental and socioeconomic conditions.When asked, farmers expressed a desire tomaintain diversity of traditional crop speciesand varieties for nutritional, cultural, andsubsistence goals, and the majority of farmerssurveyed claim to have retained all of theirtraditional crops and varieties. Their ability tocontinue to grow diverse crops and varieties on-farm as they adapt to shrinking farm sizes andother forms of agricultural change, however,will likely depend largely on gradients of ele-vation, connectivity, and resource availability.

To support an increasingly dense popula-tion, there is pressure on farmers to increasetheir involvement in the market system. Exten-sion offices are recommending the cultivation



of high-value crops such as fruits and vegeta-bles for market sale to augment subsistenceproduction, and many farmers are pursuingthis route, especially in the highlands. NGOsand religious organizations are also promot-ing and disseminating fruits and vegetables inhighland areas. In lower Gamo communities,larger fields, greater extension involvement,and less developed traditional cultivation prac-tices and social structures make market produc-tion more feasible and desirable. Several studieshave found that increased trade has the po-tential to increase on-farm diversity (Nagara-jan and Smale 2007), and this phenomenon isevident on larger Gamo farms, where farmershave the ability to add new crops to old ones.On smaller farms, though, several farmers re-ported that shortage of land leads to replace-ment of crops such as barley and Oromo potatowith new crops for market. In addition, there isin some regions of the Gamo significant migra-tion of men to towns and cities, including Ad-dis Ababa, most often to work as weavers. Theincome generated through these activities, inconjunction with shortages of labor back on thefarms, turns these households toward increas-ing market participation to meet their needs.

A second strategy used in the Gamo to adaptto smaller farms and new crops is to intensifysubsistence production by abandoning manyspecialized crops and varieties and focusing onsubsistence staples such as the most productiveenset varieties, and replacing traditional lan-draces of barley and Oromo potato with moreproductive wheat and potatoes. This strategy ismost common in the highlands, where smallfarms, fewer options for diversification, andless extension involvement make market-basedstrategies less feasible and appealing. As thehighland areas are the center of much of thevarietal diversity of traditional crops, this trendcould have serious negative ramifications forthe conservation of crop diversity in the Gamo.

A third strategy for adaptation to chang-ing agroecological conditions is one that Gamofarmers have used for millennia to buffer theirfarms from uncertain and volatile conditions.This is the utilization of the Gamo’s steep ele-vation gradient to increase options and managerisk through trade and cultivation of multiplefields. The majority of farmers surveyed cul-tivate fields at multiple elevations, increasingthe diversity of crops available to their families

and ensuring against environmental perturba-tions. Crops can be reduced or expanded in oneor more agroecological zones, and patterns oflabor or resource allocation can be shifted be-tween zones. Farmers at all elevations utilizethis strategy, with differential uses for higheror lower fields.

Steep altitudinal gradients in combinationwith local markets provide farmers with accessto food products grown at other elevations. Allfarmers living above 2,800 m reported purchas-ing crops from lower elevation markets, es-pecially maize and sweet potatoes, and manyfarmers at lower elevations reported obtainingenset or barley products from farmers at higherelevations. This system of exchange acts as asafety valve, as farmers at any elevation can in-crease or decrease their dependence on cropsgrown in higher or lower zones.

Conclusions

In heterogeneous and remote agriculturallandscapes such as the southern highlands ofEthiopia, human management of crop diversityinteracts with steep environmental gradientsto determine the distribution and richnessof crop species and varieties. Environmentalvariables related to elevation play a large rolein determining on-farm diversity; howeverelevation can also be a proxy for cultural,infrastructural, and land-use variables, andthese anthropogenic features of elevation canwork to strengthen or moderate the force ofenvironmental gradients. Differing levels ofmarket and extension access, historical and cur-rent population density, strength of traditionalsocial and cultural institutions, and patterns ofexchange between farmers also appear to playkey roles in determining on-farm diversity atspecies and variety levels. These interactionsmight also determine the strategies availableto farmers to adapt to changing demographics,land-use patterns, and market forces. Ongoingresearch into farmer exchange networks andcrop genetic diversity in the region will add toour understanding of these processes. �

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LEAH H. SAMBERG is a doctoral candidate in theDepartment of Environmental Studies at the Uni-versity of California, Santa Cruz, 1156 High Street,Santa Cruz, CA 95064. E-mail: [email protected] research focus is on ecology in human land-scapes, especially related to biodiversity, agriculture,and development. Currently she works primarily inthe highlands of Ethiopia.



CAROL SHENNAN is a Professor in the Environ-mental Studies Department at the University of Cal-ifornia, Santa Cruz, Santa Cruz, CA 95064. E-mail:[email protected]. Her main interests are agroe-cology, sustainable agriculture, nutrient cycling, andthe effects of landscape diversity on agroecosystemfunctions.

ERIKA S. ZAVALETA is a conservation ecolo-gist in the Department of Environmental Studies

at the University of California, Santa Cruz, SantaCruz, CA 95064. E-mail: [email protected]. Herresearch emphasizes the community and ecosys-tem consequences of biodiversity decline and cli-mate and atmospheric changes. Her work in theconservation and management practice arena alsoincludes collaboration with conservation practition-ers and elements of economics, public policy, andanthropology.


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