IN SITU CONSERVATION OF CROP GENETIC RESOURCES IN THE MEXICAN MILPA SYSTEM

This dissertation focuses on the theoretical modeling and empirical testing of household motivations for the in situ conservation of crop genetic resources (CGR). An original household survey is used to test whether the household diversity outcomes are different for the cropping system as a whole, for the principal crop, maize, or for the secondary crops, beans and squash. Agro-ecological characteristics and market characteristics are found to significantly affect the levels of diversity maintained by households. A review of the economic literature relevant to modeling in situ conservation is presented. A theoretical model is developed in which a household's decision to plant a milpa variety is linked to household, agro-ecological, and market variables. A household farm model appropriate to CGR conservation is presented, and extended to the case of missing markets. The agricultural ecology of the Sierra Norte de Puebla is described, as well as the principal CGR in the milpa system. The empirical methodology uses a Poisson regression, for the total number of crop varieties and for each crop group separately. The econometric work is extended to a hurdle model for sample selection, and a SUR model utilizing a Shannon diversity index as a linear measure of diversity. The results from the regressions of household level diversity show that a range of household, village, environmental, and market conditions affect the diversity outcomes. Market integration, measured by distance to a regional market, use of hired labor, and international migration, were found to negatively affect diversity outcomes. Agro-ecological conditions, measured by the number of plots, plots with different slopes, and the high altitude region, all were found to positively increase household diversity outcomes. The econometric findings were different for the combined milpa system than individual crops, and individual crops were affected by different factors. The principal crop, maize, seems mainly affected by the agro-ecological characteristics, while the levels of market integration are found to affect the minor crops, beans and squash. Conclusions are presented on the links between this study and conservation planning issues, and possible directions for future research are discussed