THE DYNAMICS OF CROP INFRASPECIFIC DIVERSITY: A

CONCEPTUAL FRAMEWORK AT THE FARMER LEVELl

MAURICIO R. BELLON

Bellon, M. R. (Centro de Ecologia, Universidad Nacional Autonoma de Mexico, ApartadoPostal 70-275. Mexico, D.F. 04510 Mexico Present address: IRRI, P. O. Box 933, 1099 Manila,Philippines.). THE DYNAMICS OF CROP lNFRASPECIFIC DIVERSITY: A CONCEPTUAL FRAMEWORK AT

THE FARMER LEVEL. Economic Botany 50(1):26-39.1996. There is an increasing concern overthe loss of germplasm diversity in areas of crop domestication. Nevertheless in these areasmany farmers continue to maintain a pool of varieties, many of them landraces, despite thefact that they have also incorporated improved varieties, and that some landraces have beeneliminated. This paper provides a framework for analyzing the decision ofa farmer to maintain,incorporate or discard a variety from hislher repertoire of varieties of one crop. It is based onan analysis of the roles that crop infraspecijic diversity can play in a farmer's well-being, howthese roles change, the limits to these changes, and some predictions and suggestions derivedfrom this framework.

La Dimimica de la Diversidad Infraespecffica: Un Marco Conceptual a Nivel del Agricultor.Existe una gran preocupacion por la perdida de diversidad de germoplasma en las areas dedomesticacion de los cultivos. Sin embargo muchos agricultores en estas areas continuan sem­brando y mantiendo un acervo de distintas variedades, muchas de elias criollas, aun cuandohan incorporado a este variedades mejoradas, y a pesar de que algunas variedades criollasya no se utilizan. Este articulo presenta un marco de referencia para analizar la decision porparte de un agricultor de mantener, incorporar 0 eliminar una variedad del acervo que deestas se conserva. Se basa en un analisis de los papeles que la diversidad infraespecijica puedejugar en el bienestar de un agricultor, como estos papeles cambian, asi como los limites aestos cambios. Tambien presenta algunas predicciones y sugerencias derivadas de este marcode referencia.

Key Words: crop infraspecific diversity; farmer's decision-making; in situ conservation.

Gennplasm diversity is the basis for farmersand plant breeders to adapt crops to heteroge­neous and changing environments and to pro­vide them with resistance to pests and diseases.Large areas planted to a single variety or a fewcultivars with similar genetic background can beespecially vulnerable to pests, diseases and se­vere weather (NRC 1993; Plucknett et al. 1987;Wilkes 1989a). There is an increasing concernover the loss of gennplasm diversity, particular­ly with the substitution of a diverse set of ge­netically variable crop landraces by a few ge­netically unifonn high yielding varieties (Brush1991; Harlan 1992; Hawkes 1983; NRC 1993;Plucknett et al. 1987). This concern is especiallyvalid in areas of crop domestication, where this

I Received 6 January 1994; accepted 30 August1995.

diversity is concentrated and where farmersmaintain not only the germplasm of local vari­eties of ancestral crop populations, but also thehuman knowledge and behavioral practices thathave shaped this diversity for generations (Bel­lon and Taylor 1993; Brush 1991). Nevertheless,there is increasing evidence that this process ofsubstitution is not as simple or common as orig­inally thought (Bellon 1991; Brush 1991, 1995;Brush, Taylor, and Bellon 1992; Dennis 1987).Farmers in these areas continue to maintainpools of varieties, many of them landraces, de­spite the fact that they have also incorporatedimproved varieties, and that some landraceshave been eliminated.

The need to conserve crop infraspecific di­versity has been recognized as important formany decades and has translated into the crea­tion of gene banks around the world and formany different crops, Le. ex situ conservation

Economic Botany 50(1) pp. 26-39. 1996© 1996 by The New York Botanical Garden, Bronx, NY 10458 U.S.A.

1996J BELLON: CROP INFRASPECIFIC DIVERSITY 27

(Hawkes 1983; Plucknett et al. 1987). Lately, anew approach to complement the former hasbeen suggested through in situ conservation (Al­tieri and Merrick 1987; Brush 1991; IPGRI1993; Oldfield and Alcorn 1987). This is thecontinued cultivation of crop genetic resourcesin the farming systems where they have evolved(Brush 1991). It seeks to maintain the habitatsand the evolutionary processes that have createdthe germplasm and depends on the active partic­ipation of farmers in that it is based on actingon farmers' reasons and incentives to maintaindiversity (Bellon 1995; Brush 1991). Clearly, tounderstand the process that leads to the main­tenance or loss of germplasm diversity in farm­ing systems, and therefore to develop and to im­plement in situ conservation strategies and pro­grams, there is a need to understand how farm­ers' decision-making is related to changes in thepool of crop varieties used in their agroecosys­tems.

The purpose of this paper is to provide aframework for analyzing the decision of a farm­er to maintain, incorporate or discard a varietyfrom his/her repertoire of varieties of one crop.Here this repertoire is defined as infraspecificdiversity. Its focus is on the crop populationsthat farmers recognize and name as distinctunits, whether landraces, improved varieties, orin the case of open pollinated crops, creolizedvarieties. It does not deal directly with allelic orgenotypic diversity, but with morphotypeswhich are what farmers control and act upon,although clearly there is an important relation­ship between them. The study of crop infraspe­cific diversity maintained by farmers at the farmlevel is important because this is the lowest levelof analysis of decision-making involved in thehuman selection and management of a crop andbecause it may account for a major part of re­gional genetic diversity, which has been shownat least for potatoes (Zimmerer and Douches1991).

This paper provides an analysis of the rolesthat crop infraspecific diversity can play in a far­mer's well-being, how these roles change withan increased integration of the farmer into themarket and the availability of new technologies,as well as some of the limits to these changes.The framework presented here is based on twoideas. The first is that farmers have a set of con­cerns associated with a crop they plant andknowledge of how each variety performs for

each concern relative to the other varieties intheir repertoire. The second is that those con­cerns change by the incorporation of the farmersinto the market, their access to new technologiesand job opportunities, and by the impact of gov­ernment policies.

THE GOODS AND SERVICES OF CROPINFRASPECIFIC DIVERSITY

Crop infraspecific diversity has providedfarmers throughout history with numerousgoods and services, both for production and forconsumption. It is still a central part of manysmall farmers' adaptive strategies to cope withheterogeneous and uncertain ecological and so­cioeconomic environments, particularly in de­veloping countries (Bellon 1991; Brush 1992;Clawson 1985). In fact, the use and maintenanceof crop infraspecific diversity by farmers can beseen as an adaptation, i.e., a way of attaininggoals and solving problems (e.g., Bennett 1976).It is important to point out that the different rolesthat crop diversity can play in the farmers' well­being are not mutually exclusive. They maycomplement each other, and in fact as it will beargued below, that is what a farmer may belooking for.

Small farmers in many parts of the world areconfronted with complex and heterogeneous en­vironments (Brush 1980; Kirkby 1973). Crop di­versity allows a farmer to farm in a variety ofenvironments characterized by different soilqualities, temperature and rainfall regimens, to­pographies, exposures, etc. (Brush, Carney, andHuaman 1981; Lando and Mak 1994; Richards1986). For example, Bellon and Taylor (1993)have shown that small farmers in SoutheasternMexico keep different maize varieties to fit dif­ferent soil qualities. As pointed out by Brush(1992:147): "Environmental heterogeneity cre­ates the opportunity for selection and isolationof different crops and varieties that are moresuited to one set of circumstances."

Small farmers are faced with many sources ofproduction risks and uncertainty, e.g., rainfallvariability, and the occurrence of frost. Themaintenance of crop diversity has been associ­ated with the farmers' ability to manage theserisks (Clawson 1985; Feder, Just, and Zilberman1985; Lipton 1968; Roumasset 1976). Clawson(1985) shows how crop varieties with differentmaturation periods are used by small farmersthroughout the world to insure a sufficient food

28 ECONOMIC BOTANY [VOL. 50

supply. In the economics literature, it has beenestablished theoretically that by simultaneouslyplanting crops or varieties with different vari­ances and/or covariances of returns, farmersmay minimize risks while maximizing mean re­turns (Just and Zilberman 1983), or minimizethe probability of falling below a minimum sub­sistence level (safety-first rules, e.g., Roumasset1976).

Crop infraspecific diversity has been used byfarmers to schedule farm operations, such asplanting, weeding and harvesting, in such a wayas to spread labor during the growing season andavoid or minimize labor bottlenecks (Conklin1957; Richards 1986).

Crop diversity has helped small farmers tocope with different pests and pathogens, partic­ularly in the absence of pesticides (Glass andThurston 1978). The natural resistance of certaincrop cultivars to certain pests and diseases,which have developed through a long coevolu­tionary process (Glass and Thurston 1978), hasbeen identified as one of the key contributionsof the maintenance of crop genetic diversity toplant breeding and modem agriculture (Hawkes1983; NRC 1993).

Many cultures use crop infraspecific diversityfor ritual, prestige or to forge social ties. Forexample, the use of native varieties of potatoesin the Andes as a favored gift to strengthen so­cial ties, sometimes referred as "papas de re­galo" (gift potatoes), or as part of wages andduring reciprocal labor exchange when mealsare served (Brush 1992). Perales (1992) used anumber of culture indicators, such as the obser­vance of various kinds of ritual practices, thathelped to explain the maintenance of maize di­versity among the Popolucas in Mexico. Sutlive(1978) found that the Iban of Sarawak locate aspecial ritual segment in the middle of a fieldwhere a special rice variety is planted.

The contribution of crop infraspecific diver­sity to a farmer and his/her family's nutritionand diet is not as obvious as that of interspecificdiversity (e.g., Heuret and Heuret 1980). Nev­ertheless, when one crop is very important in thediet, it can be important to supply variety to anotherwise monotonous diet, in terms of differenttextures, flavors and uses (Hernandez X. 1985).For example, six hundred and five ways of pre­paring maize, associated with different maizevarieties, have been reported for Mexico, where

maize is and has been the main staple (MuseoNacional de Culturas Populares 1982).

The roles of crop infraspecific diversity de­scribed above refer to an actual use by farmers.They have what some economists refer to as usevalue (Pearce and Turner 1990). But as theseeconomists point out, this is only a part of thetotal economic value of something, togetherwith two other categories: option value and ex­istence value. Option value is the value of some­thing as a potential benefit as opposed to actualpresent use value (Pearce and Turner 1990). Theconservation of diversity may have a positiveoption value, since it keeps options open, partic­ularly because farmers may not know the futurebenefit or availability of particular varieties(Brush, Taylor, and Bellon 1992). For example,several farmers whom I interviewed in Chiapas,Mexico said that they planted small areas of acertain maize variety "not to lose the seed", be­cause it was a "good maize" that could be use­ful in the future, although they did not have aparticular idea of how or when. Finally, we haveto recognize that humans can value diversity forits own sake. This may be understood as an ex­istence value for crop diversity. For example, asargued by Hawkes (1983), the search for beautyhas played an important role in the developmentand maintenance of infraspecific diversity inmany crops (clearly, beauty is also related to thecultural significance of crop infraspecific diver­sity).

FARMERS' KNOWLEDGE OFCROP DIVERSITY

The fact that traditional farmers have a welldeveloped knowledge of their crops and crop va­rieties has been well documented by humanecologists, anthropologists and ethnobiologists(Bellon 1991; Berlin, Breedlove, and Raven1974; Brush, Carney, and Huaman 1981; Boster1983; Conklin 1957; Hames 1983; Mapes 1987).

Many workers have documented an extensiveknowledge of ecological, agronomic and con­sumptive characteristics of varieties for manycrops in their areas of domestication such asmaize in Mexico (Bellon 1991; Hernandez X.1985; Mapes 1987); potatoes in Peru (Brush,Carney, and Huaman 1981); manioc in the Am­azon (Boster 1983; Hames 1983); and rice inSoutheast Asia (Conklin 1957; Lambert 1985;Lando and Mak 1994; Sutlive 1978). In manyinstances this knowledge has been systematized

1996] BELLON: CROP INFRASPECIFIC DIVERSITY 29

in a regular system of nomenclature, organizedin a taxonomic manner, i.e., folk taxonomies(Brush, Carney, and Huaman 1981; Mapes1987). Furthermore, in at least one instance, aremarkable degree of correspondence betweenfolk recognition of potato varieties and the re­sults of isozyme analysis at the village level hasbeen found (Quiros et al. 1990). This knowledgemay be used to make decisions regarding spe­cific planting and management patterns, storage,culinary aspects and rituals (Bellon 1991; Boster1983; Hames 1983; Johnson 1974; Lambert1985; Sutlive 1978).

The knowledge of crop diversity is dynamic,as is crop diversity itself (Bellon 1991). The ex­change and transport of germplasm is a commonhistorical pattern all over the world, which con­tinues with the introduction of new crops andimproved varieties. Farmers are continually in­corporating and discarding crops and varieties(Dennis 1987; Louette 1994; Sperling and Loe­vinsohn 1993; Richards 1986). These processesrequire the maintenance and generation ofknowledge. Farmers constantly develop and ex­periment with technological alternatives (Feder,Just, and Zilberman 1983; Johnson 1972), whichis particularly true for new germplasm (Bellon1991; Richards 1986; Soleri and Cleveland1993). Much of the new information acquired istransmitted from farmer to farmer. As observedby Lambert (1985) among Malay rice farmers,they constantly experiment with rice cultivars,even with well known ones. Individual house­holds test one variety against another, a processof matching varietal performance to small butsignificant differences in localized habitats. Ex­perimentation and communication among farm­ers are the basis of the development of their cropknowledge and the inclusion of new crops andvarieties. Both are important means to deal withnew and unproved germplasm because they al­low farmers to know and evaluate it withoutjeopardizing their livelihood or scarce resources.They continue to be the basis of the incorpora­tion of new varieties and crops in many farmingsystems throughout the world.

THE Loss OF CROP DIVERSITY

Farmers and their agroecosystems are not stat­ic, but are constantly changing. Farmers facenew challenges and opportunities and experi­ment with new technologies, modifying old onesas well. In this dynamic process, an important

concern is the loss of crop diversity. This losshas been associated with increasing populations,the expansion of the agricultural frontier, the de­crease in fallow cycles, and particularly with anincreased integration of small traditional farmersinto the market, both as producers and consum­ers (Brush 1991; Brush, Taylor, and Bellon1992; Harlan 1992; Hawkes 1983).

Market integration allows farmer householdsto sell their products in new markets and to haveaccess to goods and services produced outsidetheir communities. As producers, farmers gainaccess to new purchased inputs, such as fertil­izers, agrochemicals, machinery, expertise andnew improved modern varieties (MY's). Theycan specialize in a few crops and sell the sur­pluses, so that as consumers they can purchaseproducts, both those that they used to produce,such as the local subsistence crops (e.g., maize,rice, potatoes), as well as completely new ones,such as vegetables or soft drinks. They, or theirfamilies, can work outside their own farms asnew labor opportunities become available, innearby or far away places. Emigration, temporalor permanent, of the farmer or of members ofthe household can become an important sourceof income, savings and investments, as well asa new way to manage risks. This can be accom­plished through the purchase of insurance, orsimply by remittances from emigrants, that arean independent income source (Stark 1982).These represent alternative types of risk man­agement reducing the necessity of crop diversityto fulfill this role.

Clearly, many of the goods and services pro­vided by crop diversity can be substituted byalternatives that can be purchased in the market.A farmer can specialize in a few activities andcrops which can be sold to purchase the substi­tutes of crop diversity. Hence, the value of cropdiversity decreases for the farmer and so maythe diversity maintained on his/her farm. TableI shows some of the goods and services provid­ed by crop diversity and some of the possiblesubstitutes obtained through the market.

Government policies aimed at increasing thefood supply, particularly for increasing urbanpopulations associated with processes of indus­trialization, have also affected diversity. Govern­ments have provided infrastructure, modern in­puts and subsidies to farmers, favoring andsometimes forcing specialization. In many casesthey have imposed restrictions on what farmers

30 ECONOMIC BOTANY

TABLE 1. FARMERS' CONCERNS AND CROP INFRASPECIFIC DIVERSITY.

[VOL. 50

Farmers' concerns

Environmental heterogeneity (soils,temperature, rainfall, exposure, pho­toperiods, etc.)

Pests and pathogens

Risk management

Culture and ritual

Diet

Goods and services providedby crop infraspecific diversity

ability to farm in a variety of en­vironments

ability to reduce crop losses dueto pests and pathogens

ability to reduce production risks(drought, lodging, frost)

ability to fulfill rituals, provideprestige, forge social ties

a varied diet

Substitutes for cropinfraspecific diversity

irrigation, chemical fertilizers,soil amendments

pesticides

commercial or government insur­ance, remittances, off-farm la­bor

purchased ritual and prestigeitems, wage labor

commercial products

can and cannot do, either through legal process,or through imposing conditions on the access todesirable inputs. For example conditioning cred­it to the compulsory planting of MY's, in thebelief that it will increase food production.

However, the process of crop diversity loss isnot as simple as it seems, nor as automatic. Spe­cialization is not always possible or desirable.Market imperfections are common throughoutthe developing world (Brush, Taylor, and Bellon1992; de Janvry, Fafchamps, and Sadoulet 1991;Plattner 1989). In many rural areas a few peoplecontrol the marketing of inputs and productsbought and sold by farmers and their families,and can easily manipulate prices and transac­tions conditions (e.g., form of payment). Infor­mation is scarce and expensive. Products maybe of heterogeneous quality, which may be dif­ficult to establish prior to their purchase (Plattner1989). The performance of new inputs, such asfertilizers and improved varieties may be un­known, and therefore may need to be used forseveral seasons to be properly evaluated. In fact,learning behavior by farmers and input rationingin imperfect markets have been used to explainwhy farmers would plant several varieties si­multaneously (Smale, Just, and Leathers 1994).In many cases, the products supplied by the mar­ket are poor substitutes for the goods and ser­vices provided by crop diversity. For example,farmers and their families may have tastes thatmarket products cannot fulfill. As Brush, Taylor,and Bellon (1992:368) have stated:

Inefficient markets or exchange systems may not beable to satisfy consumption demands for diversity inindividual farm households, and these market im-

perfections may encourage diversity in productionon individual household farms.

Additionally, market integration can increasethe vulnerability of farmers to outside factors.No longer does a farmer have to cope only withrainfall variability or the probability of frost, butalso with price variability of the products soldor bought, such as purchased inputs. Getting anoff-farm job or migrating successfully is not asure event. A farmer and his/her family have totake into consideration the probability of gettingand maintaining an off-farm job, or the risks ofsending out family migrants. Factors that arelargely removed from a farmer's sphere of actionhave a large impact on herlhis well-being, suchas world prices for commodities, raw materialsand industrialized products, national and inter­national policies, trade agreements and propertyrights regimes, over which s/he has little or nosay, control, or understanding.

Nevertheless, in the new contexts of marketintegration, as in the past when farmers haveadapted to rainfall variability or heterogeneousenvironments, many farmers are developingstrategies to cope, and crop diversity can playan important role. For example, farmers maymaintain landraces that can withstand delays inweeding or fertilizer application if they cannotcontrol the delivery of inputs such as herbicidesor fertilizers (Bellon 1991; Bellon and Taylor1993).

There is increasing evidence that small farm­ers continue to maintain crop infraspecific di­versity, and not only among poor farmers inmarginal areas, but also among relatively well­off farmers in good areas, producing for the

1996] BELLON: CROP INFRASPECIFIC DIVERSITY 31

market and with access to modern inputs (Bellon1991; Bellon and Taylor 1993; Brush 1995). Thefact that crop diversity is not necessarily or com­pletely replaced by market integration and theavailability of new technologies, challenges thenotion that its conservation condemns farmers toa lower living standards, an argument that hasbeen made to reject in situ conservation by theearly planners of the international system ofgermplasm conservation (Frankel 1970; Wil­liams 1988).

A CASE STUDY FROMCHIAPAS, MEXICO

The framework which I will present in thenext section is based on detailed fieldwork inVicente Guerrero, a community of small peasantmaize farmers in central Chiapas. Therefore, Iwill present a short description of this work andthe pertinent findings. The research site, themethods, and the results have been extensivelypresented and discussed elsewhere (Bellon1991).

These farmers produce maize for self-con­sumption, as well as important surpluses for thenational market. They practice plow and swid­den agriculture, in relatively good soils, with fa­vorable weather for maize production. Tradition­al and modern technologies coexist, with vary­ing rates of fertilizers, herbicides, pesticides andan improved variety in both systems. Neverthe­less, several characteristics associated with amore traditional agriculture are still common,such as the use of teams of oxen, wooden plowsand the dibbling stick, and the utilization of sev­eral maize varieties, induding landraces. Thesefarmers have benefited from the developmentpolicies of the Mexican government. They haveaccess to government provided credit, crop in­surance, grain storage and marketing facilities,and produce important maize surpluses, mainlysold to the government marketing facility. An­other advantage of this community is that it islocated dose to the state capital and communi­cated by a good dirt road.

Although improved varieties have been avail­able for the last thirty years, and some have beenadopted, these farmers continue to plant up tofifteen different varieties, belonging to six dif­ferent races. But at the same time there havebeen changes in the diversity of the varietiesmaintained there. New varieties have been intro­duced and become very important, while others

have decreased in importance, although theyhave not necessarily been eliminated (Bellon1991; Bellon and Brush 1994). Clearly, maizevarietal diversity has been dynamic in this com­munity.

There are two central findings of my workwith these farmers. First is that they have a setof concerns associated with the performanceof their maize varieties, as well as a knowl­edge base of how they perform for each con­cern in relationship with each other, and canrank them accordingly. Farmers have threegroups of concerns, related to: ecology, man­agement and use. Table 2 presents the farmers'concerns, the crop trait involved, and the waythey rank the performance of their three mainvarieties with respect of each concern. Thesecond is that no variety alone seems to ad­dress all of the farmers' concerns, and the pro­cess of varietal adoption is more complex thana simple dichotomous decision on adopt! donot adopt. Farmers are interested in varietieswith contrasting traits that fit different needsand constraints, rather than a single plant witha particular trait-such as high yield. The factsthat (a) farmers have multiple concerns thatare reflected in multiple criteria to select whatvarieties to plant and how to manage them; (b)that they can rank each variety according tothese criteria; and (c) that they maintain vari­eties with different traits, have also been re­ported by others (Lambert 1985; Lando andMak 1994; Richards 1986; Sperling, Loevin­sohn, and Ntabomvura 1993).

A FRAMEWORK FOR THEDYNAMICS OF CROP DIVERSITY

The framework presented here is a general­ization of the findings of my study in Chiapas,complemented and supported by other researchand results reviewed above. Although based onmaize, it could be generalized to other crops,and though it focuses on infraspecific diversity,it could be used for interspecific diversity aswell. Varietal change at the farmer level is notonly a systematic process, but it also has im­portant random elements, such as, the accidentalloss of desired varieties (Sperling and Loevin­sohn 1993), however, the framework presentedhere is limited to the systematic aspects of thisprocess. This framework is based on the follow­ing five assumptions:.

32 ECONOMIC BOTANY [VOL. 50

TABLE 2. FARMERS' CONCERNS AND RANKING OF THEIR THREE MAIN VARIETIES, VICENTE GUERRERO,CHIAPAS, MEXICO.

Variables Ranking of varieties

Improved Creolized TraditionalConcerns Variety traits Gradient variety variety* variety

Midsummer drought growing cycle short!long first second thirddrought resistance high/low third second first

Strong winds (lodging) plant stature short/tall first second thirdstalk strength strong first second third

Soil quality good for poor soils good/bad third second firstneeds good soil needs/does not need yes no no

Availability of labor for ability to withstand de- high/low third second firstweeding lays on weeding

Availability of fertilizer quantity of fertilizer re- high/low first second thirdquired to yield well

Availability of labor for fer- ability to withstand de- high/low third second firsttilizer application lays on fertilizer ap-

plicationYield yield/volume high/low third second first

yield/weight high/low first first secondStorage ability to withstand high/low third first second

long tenn storageUse appropriate for self- more/less second first first

consumptionTaste appropriate for market more/less first first second

taste better second second first

• Creolized variety, an originally improved variety which has been mixing with local germplasm for thirty years, see Bellon and Brush, 1994.Source: Bellon, 1991; Bellon and Taylor, 1993.

(1) A farmer has a set of concerns, i,e" mattersof interest or importance to himlher. For ex­ample, some are related to production suchas drought resistance, others to consump­tion, such as storability, This set of concernscan be represented as a vector, where eachvariable is a concern,

(2) A farmer has access to a set of varieties,Each variety has a set of properties, for ex­ample, plant stature or resistance of the har­vested grains to weevil infestation, that al­lows it to perform in a particular way withrespect to each of the farmer's concerns,These properties are related to the farmer'sconcerns of wind lodging and storage,Therefore, for each concern there is a vari­etal property. For each variety, this can berepresented as a vector, with each propertyas a variable, The set of varieties availableto a farmer can be represented as a matrix,which is the result of grouping the individ­ual variety vectors.

(3) A farmer knows each of the varieties' prop­erties and can associate each of them with

one of herlhis concerns. This knowledge isgained by working with the varieties yearafter year, communicating with other farm­ers and by experimenting with them for newmaterial.

(4) A farmer evaluates each of the varieties'properties with respect to their performancewith regard to each concern. A farmer canrank each variety relative to the others withrespect to each of herlhis concerns from bestto worst.

(5) A farmer tries to address each concern withthe best variety, i.e., the one that ranks thehighest for a particular concern.

With these assumptions it is possible to ana­lyze the process of inclusion, elimination andmaintenance of any single variety in a set ofvarieties, i.e., the dynamics of variety diversity.

MAINTENANCE

Several varieties are maintained (i.e., theycontinue to be planted by the farmer) if each oneof them scores high for a different subset of con-

1996] BELLON: CROP INFRASPECIFIC DIVERSITY 33

cerns (and therefore low for the rest). For ex­ample, if a farmer has only two concerns, suchas drought resistance and yield, a variety thatscores high for drought resistant but low foryield will be maintained together with a varietythat scores low for drought resistance, but highfor yield. Varieties complement each other infulfilling farmers' concerns.

DISPLACEMENT

One variety displaces another, (i.e., eliminatesit from the set of varieties planted by a farmer)if it scores higher for the same subset of con­cerns as another one, and either scores at leastequal to this one for the rest of concerns or thereis a third variety or set of varieties that rankhigher than those two in the rest of the concerns.The limit of the displacement is when one va­riety scores higher than all others in all of thefarmers' concerns, and therefore eliminates themall.

INCLUSION WITHOUT

DISPLACEMENT

A variety is included in the set of varietiesmaintained by a farmer if it scores higher thanthe others for a subset of concerns, but the restof varieties continue to rank higher for othersubsets of concerns.

Clearly, to understand the dynamics of varietydiversity it is necessary to study changes in: (a)farmers' concerns and (b) variety performance.The concerns used in the decision about plantinga crop can decrease because of integration to themarket or the availability of new technology.The concerns may still be there, but be fulfilledthrough a different process associated with mar­ket integration. Hernandez X. (1985), for ex­ample, has argued that a diverse set of varietiesare important to avoid a monotonous diet.Therefore if due to market integration, a farmercan buy a larger variety of foods, the importanceof varietal diversity to avoid dietary monotonymay decrease substantially. This means that va­rieties that rank high in the subset of concernsnow fulfilled through market participation willno longer be important and needed, and there­fore may be eliminated, other things beingequal. The vector of concerns decreases in size.Another example may be a variety that is resis­tant to weevils in storage, may become irrele­vant if an insecticide becomes available to in­crease storage life. On the production side, if a

variety was well suited for conditions of low nu­trient availability, it would loose its competitiveedge if fertilizers became available. If a new va­riety, such as, but not necessarily, a modern va­riety, that ranks high for all of a farmer's con­cerns is made available, this one should displaceall others even if concerns stay the same.

The concerns involved in planting a crop canincrease as well. Integration with the market orthe availability of new technologies can createnew opportunities for a farmer, and new con­cerns. For example, if transportation costs arehigh and marketing difficult, farmers may not beconcerned to produce crop surpluses. However,if the marketing infrastructure is improved, afarmer may be able to sell surpluses and there­fore become interested in producing them. Ifother concerns are not affected, the farmer mayincorporate a variety that yielded high, eventhough it may rank low with respect to the otherconcerns, such as storage or taste. Therefore, thenumber of varieties maintained by a farmershould increase.

Most likely the processes of crop diversityloss that have occurred worldwide are a com­bination of all the changes described above. Thefarmers' concerns have been reduced due to in­tegration to the market and new technology, in­cluding the elimination of many concerns, thestrengthening of some and the introduction of afew others, but with a net effect of a smaller andless complex concern profile. At the same time,new varieties, especially improved ones thatrank high with respect to this reduced concernprofile, have been introduced, displacing othersand leading to a few varieties being planted bymany farmers and occupying large areas. Nev­ertheless, among farmers who have various anddifferent concerns, crop infraspecific diversitymay be maintained because it is unlikely thatone variety may displace all others, given thatimproving a crop for certain traits may implylosses in other traits. For example, Harlan (1992)points out that alleles for disease resistance gen­erally have negative effects on yield in the ab­sence of the disease, and sometimes even in itspresence. In many annual crops, a negative as­sociation between yield and competitive abilityhas been found (Donald and Hamblin 1983).

A central issue that remains to be studied ishow farmers rank their concerns and how theymay trade off one against another. What are thelimits of substitution between a good perfor-

34 ECONOMIC BOTANY [VOL. 50

mance with respect to one concern and a badperformance with respect to another. For exam­ple, at what point does an increased yield stopcompensating for inferior storage quality ortaste. These trade-offs may be an importantcomponent of the cost of maintaining diversity.The fact that maintaining diversity can be costlyhas been recognized. The selection, identifica­tion and storage of a diverse set of seeds, as wellas the farm management of a diverse rather thanuniform crop may be inherently time- and man­agement-intensive activities that may conflictwith more remunerative ones (Brush, Taylor, andBellon 1992), Nevertheless, specializing in a va­riety that can only fulfill a few of the farmer'sconcerns can also be costly to him/her.

The ranking of concerns and the trade-offsamong them, as well as the trade-offs betweenthe added costs of maintaining diversity and thebenefits of fulfilling a diverse set of concernsremain as an empirical matter of study. Never­theless, I speculate that these trade-offs are moreimportant in terms of deciding the area planted,than in terms of just deciding whether or not toplant a variety. Even a variety with a poor per­formance with respect to many concerns, i.e.,with high costs, can be planted in small areaswith minimum investment to fulfill just one con­cern. For example, I observed than in southernGuanajuato, Mexico, small farmers plant a"mafz negro" (black maize)---even though thereis no market for it and it is difficult to store­in very small areas (about 0.1 ha) because it isconsidered to have good taste and has some spe­cial uses.

PREDICTIONS OF THE FRAMEWORK

The process of change in crop diversity pre­sented here pertains to an individual farmer, butcan be easily generalized to a set of farmers.Farmers can be grouped by the concern profilesthey share, which in turn should be related tothe environment in which they farm and the de­gree of market integration. Farmers with similarprofiles should maintain comparable levels andtypes of diversity, while farmers with differentconcern profiles should vary. A way to groupfarmers is through the use of typologies, gen­erated by a set of variables (e.g., Montanez andWarman 1985, and CEPAL 1982 for maizefarmers in Mexico). For example, farmers canbe grouped by their degree of participation inthe market of the crop of interest, both as sup-

pliers and consumers, their access to resources,such as land, capital and labor, the use of spe­cific technologies such as machinery, and theenvironments they use, such as the soils, thesource of water, etc. Farmers grouped in a typeshould experience similar ecological, technolog­ical and socioeconomic conditions, and thereforeshould have similar concern profiles for theircrop varieties.

For example, farmers could be classified into:(1) subsistence farmers, (2) surplus farmers and(3) commercial farmers. The first group mayonly produce a crop for self-consumption, butstill may need to purchase varying, and in manycases, important quantities of it. They may farmsmall areas, in marginal environments and off­farm labor may be important to their economicsurvival, with family labor playing a key role inproduction. These farmers may be concernedwith varieties well adapted to marginal environ­mental conditions, that require low managementand inputs and are therefore cheap to produce interms of labor and capital, do not competestrongly with off-farm labor, store well, maygenerate subproducts such as fodder, and fulfilldifferent uses in their diet with distinct tastes.Yield although important may be subordinate tothe other concerns.

Surplus farmers may produce a crop both forself-consumption as well as surpluses for themarket. This crop may be the main economicactivity. They may have medium-size farms,with a mixture of good and marginal environ­ments, and may perform some off-farm labor asa complement to their economic survival strat­egy. They may combine family and hired laborin their production. These farmers may have tobalance their concerns for self-consumption withthose for the market. Yield may be important forcertain varieties, while for others, characteristicssuch as storage, subproducts (e.g., fodder), andthe fulfillment of different uses in their diet maybe of interest.

Finally, commercial farmers may produce acrop exclusively for the market, self-consump­tion being irrelevant. They may farm large areas,with good environmental conditions such as ir­rigation or good rainfall and high quality soils.The use of family labor for production may beunimportant, but hired labor may be very im­portant. These farmers may be concerned withvarieties that are high yielding, respond well tohigh rates of inputs, can be planted at high den-

1996] BELLON: CROP INFRASPECIFIC DIVERSITY 35

sIlles, have low and homogeneous stature andare well adapted to the use of machinery. There­fore, these farmers may be the most likely tofrequently purchase certified seed of MV's,which has been specifically bred for these con­ditions.

One may expect different degrees of diversityto be maintained by each of these groups. Thelowest diversity may be associated with thecommercial farmers, highest with the surplusfarmers, and intermediate for the subsistencefarmers. Commercial farmers have only marketconcerns, such as obtaining a high yield and agood quality grain with low humidity. They mayfarm on good and homogeneous environmentalconditions, such as flat areas of high qualitysoils, and have more resources (which may al­low widespread application of inputs). For sub­sistence farmers, the main concerns may be re­lated to self-consumption, low competition offarming with off-farm labor and farming in mar­ginal environments with limited resources(which may limit their ability to modify envi­ronmental conditions through the application ofpurchased inputs). The environments in whichthey farm, though marginal may be homoge­neous since they farm small areas. Finally, onemay expect the largest diversity to be among thesurplus farmers because they have to balancetwo groups of concerns: the market and self­consumption. They may farm larger areas,which may provide a more heterogeneous en­vironment, and having more resources may beable to afford inputs, but only for certain areasor at different rates according to field or variety.They may be the most likely to have a combi­nation of varieties to fulfill their contrasting con­cerns. It is important to point out that one mayalso expect to find different sets of varietiesmaintained by each group, because they are re­sponding to different concerns and require dif­ferent combinations of traits.

Consumption concerns, such as taste, differ­ent uses, and storage may be more important forfarmers for whom a certain crop is a main com­ponent of their diet. Since this is the case for thepoor, one may expect that these types of con­cerns may play a more important role in themaintenance of diversity among subsistencefarmers, but still may be present among surplusfarmers since they also produce for self-con­sumption.

There is the common perception that indige-

nous people maintain more crop diversity thannon-indigenous (e.g., Hernandez X. 1985). Ifthis is true, this framework suggests that the twogroups should have different concern profiles. Itmay be of interest to distinguish the extent towhich these differences are related to culturalfactors or to levels of poverty and discrimina­tion. Generally indigenous people have distinctcultural traditions, but are also poor and objectsof discrimination. A comparative study of con­cerns between indigenous and non-indigenousfarmers may allow the identifications of factorsthat shape their concerns, and how they differ.For example, if culture is important, one mayexpect to find profiles with different taste andritual concerns between groups.

Similarly, it may be of interest to investigatethe differences in concerns and their ranking be­tween males and females. The role of females inthe selection and management of crop diversityis increasingly being recognized (CGIAR 1994;Sperling, Loevinsohn, and Ntabomvura 1993).Even within a farming household, males and fe­males may have not only different, but also con­flicting interests (Poats, Schmink, and Spring1988), which may have an impact on the selec­tion and management of crop diversity. This isan area still poorly understood, that merits fur­ther research.

To test this framework it will be important toidentify varieties that have been lost or replaced,as well as to evaluate the concerns they havefulfilled and their performance in this respect.Admittedly, this may restrict the research to va­rieties that have been changed recently so thatfarmers remember them. Another approach willbe to study the changes in areas planted to par­ticular varieties or the number of farmers thatused to plant a variety and the number that con­tinues to do so. Varieties may not be completelyreplaced, but only decrease in their importanceas the concern profiles of certain farmerschange, while others remain constant. The studyof the differential loss and replacement of vari­eties among farmers, and the extent to whichthese are associated with specific groups ortypes of farmers are important means to test thisframework.

The concept of farmers' concern profiles andtheir interaction with crop traits is a way to de­scribe and formalize farmers' selection. Thefarmers' concern profiles link crop traits to thefarmers' well-being. Behind those crop traits,

36 ECONOMIC BOTANY [VOL. 50

ISocioeconomic I I Cultural 'Ifactors factors

~--

"

Government I IEnvironmental Ipolicies factors

1·

L •:r~-----~II'-""__----l

Farmers' concerns Ir--- I<-- ....,.... .....J

" "

I Farmers' knowledge Ih

Farmers' decision­making

1

Diversity management:maintain/discard a variety;number of varieties;seed flows;seed management;area/variety;hybridization/isolation;tolerate weedy relatives

Crop genetic populationstructure

Crop traits: yield, plantstature, drought resistance,

etc.

--

--

I Natural Selection I

Fig. 1. A conceptual model of a fanner's management of diversity.

there is the genetic structure of the crop popu­lation in a particular farming system. Since theperformance of the variation present in thesetraits with respect to a farmer's concern profiledefines what stays and what goes, then this con­cern profile should have an important impact onthe genetic structure of the crop population. Fig-

ure I presents a conceptual model of the rela­tionships described here. This model links thedifferent variables discussed, and also acknowl­edges the fact that natural selection plays an im­portant role in the crop genetic structure, andthat environmental factors affect the expressionof crop traits.

1996] BELLON: CROP INFRASPECIFIC DIVERSITY 37

•

,

Clearly, farmer selection plays a central rolein the genetic structure of a crop population andits evolution. The genetic implications of farmerselection are complex and require further study.They may depend on the crop, its reproductivesystem (sexual or asexual, open or self pollinat­ing, etc.), the nature of the crop varieties in­volved, such as landraces or MV's and othermanagement factors such as seed selection, iso­lation, hybridization with other varieties or croprelatives (e.g., Bellon and Brush 1994; Louette1994; Wilkes 1989b).

Exploring the specific interactions betweenprofile concerns, the variation present in the va­rieties maintained by a farmer and the geneticstructure of the crop population are beyond thescope of this paper. Nevertheless, I suggest thata large concern profile, fulfilled through the useof several varieties may be associated with themaintenance of many traits that are not selectedfor (those where the varieties are inferior), butstill maintained in the population. For example,in a concern profile with nine concerns, wherethree varieties are maintained because eachscore high for three different sets of three con­cerns, the traits and the genetic structure asso­ciated with the other six concerns, may be main­tained as long as they are not detrimental. Thevariation that is not specifically selected for, butstill maintained, may become valuable underdifferent circumstances and may be the basis forthe continued evolution and adaptation of germ­plasm. But with a short concern profile, that isfulfilled by only one variety, this variation maynot be present, limiting the opportunities forevolution and adaptation, a concern of special­ization.

CONCLUSIONS

To understand the loss of germplasm diversityin farming systems and to develop and imple­ment in situ conservation, there is a need to re­late a farmer's decision-making to the pool ofvarieties that slhe maintains. In this paper I pres­ent a framework to accomplish this. It is basedon the recognition that the size and qualities ofthe repertoire of varieties that a farmer has, de­pends on hislher decision to maintain, incorpo­rate or discard a variety. This in tum may be theresult of a continuous evaluation of all availablevarieties with respect to a set of concerns, thatinclude ecological, technological and use as­pects. Furthermore, these concerns change with

increased market integration, availability of newtechnologies and by the impact of governmentpolicies. An important suggestion of this frame­work is that by keeping a large array of varietiesto fulfill specific concerns, farmers may bemaintaining a large degree of diversity which isof no direct value to them, but may becomevaluable under different circumstances and maybe the basis for the continued evolution and ad­aptation of germplasm.

ACKNOWLEDGMENTSFunding for this paper was provided by the Centro de Ecolog!a. Univ­

ersidad Nacional Autonoma de Mexico. I wish to thank Janet Lauderdale,Melinda Smale. Robert Tripp. Daniel Buckles. Sushi! Pandey and Ger­ardo Segura for helpful comments on an earlier draft of this paper.

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