Recent micro-economic studies of in situ conservation of crop diversity focus on competition between modern and traditional varieties of major food crops. Our paper offers a different, crop system, approach and a limited-dependent variable econometric technique to model in situ conservation of both intra- and infra-species crop diversity in a context of heterogeneous ecological and market environments, using unique household-farm data from Mexico. Our findings reject separability and indicate that market integration significantly reduces crop diversity. They underline the importance of studying diversity in the context of larger cropping systems and economic environments.

Worldwide, the number of genebanks1 and the amount of seed stored in them has increased substantially over the past few decades. Most attention is focused on the likely benefits of conservation, but conserving germplasm involves costs whose nature and magnitude are largely unknown. Moreover, these costs place a lower bound on the benefits deemed likely to justify the expense of conserving seed. In this study, we compile and use a set of cost data for wheat (Triticum aestivum L.) and maize (Zea mays L.), stored in the CIMMYT genebank to address a number of questions. The marginal costs of holding an existing accession for one more year are presented, along with the costs of conserving saved seed for the life of the genebank (taken here to be 40 yr), and in perpetuity We also investigated the scale economies evident in the CIMMYT genebank operation as a basis for assessing the economics of consolidating several genebanks. For accessions known to satisfy viability requirements, it costs just $0.19 and $0.93 to carry over an existing accession of wheat and maize respectively, for one more year; $7.19 and $30.24 to store an accession of each crop for the life of a genebank, and $10.26 and $58.85 to conserve accessions in perpetuity. Under baseline assumptions about interest rates, capital depreciation, and regeneration regimes, the present value of conserving the existing accessions in perpetuity at CIMMYT is $8.86 million—$3.87 million for storing the 123000 wheat accessions and $4.99 million for the 17000 maize samples. Maintaining the current level of effort to distribute accessions free‐of‐charge to those who request them would cost an additional $5.28 million in perpetuity.

This chapter elaborates a household model to address the way that social and economic factors can affect the process of genetic erosion in the Mexican milpa system, counting minor intercropped species along with principal staple crops. The study presented in Chapter 2 was implemented in one of the sites analysed here. A number of models presented in Part III are based on the household model developed in this chapter. The household model joins a farm production function, a household consumption function and market-related constraints on market availability in order to create an inclusive general model. Testable hypotheses are developed from the theoretical model, which are applied in reduced form using a limited dependent variable approach. Migration is one of the most important economic forces in rural Mexico, and the econometric application focuses on how migration can affect diversity through both income and labour market effects. Data indicate that for these farmers, production and consumption decisions cannot be separated. Migration does affect diversity but is differentiated between internal and international migration. Migration within Mexico appears to support crop diversity in the milpa system through remittances, while international migration reduces it through displacing household labour. Specifications with household and village-level variables for the migration are compared and offer similar findings.

This chapter builds on the household model presented in Chapter 5 [Missing markets, migration and crop biodiversity in the milpa system of Mexico: a household-farm model, by van Dusen, M. E., pp. 63-77] by exploring the role of social institutions in household access to planting material and use of crop biodiversity. Two types of institutions are analysed: (i) local community groups to which a household may belong and (ii) sources of planting material and agricultural information. Findings from a household survey implemented in two districts of Samarqand, Uzbekistan, provide a description of the diversity of fruits and nut trees, as well as the nature of systems for planting material. Econometric analysis reveals a linkage between participation in community groups and the levels of fruit and nut tree diversity managed by households. No relationship is found between the type of institution used to obtain genetic material and the level of diversity in orchards. Household participation in community groups influences the type of institution used for access to genetic material, however.

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