The economic determinants of cereal crop diversity on farms in the Ethiopian highlands

Abstract

In less favoured areas such as the highlands of Ethiopia, farmers manage risk through land allocation to crops and varieties since they cannot depend on market mechanisms to cope. They also grow traditional varieties that are genetically diverse and have potential social value. Supporting the maintenance of crop and variety diversity in such locations can address both the current needs of farmers and future needs of society, though it entails numerous policy challenges. We estimate a model of crop and variety choice in a theoretical framework of the farm household model to compare the determinants of crop and variety diversity, revealing some of these policy considerations. Farm physical features and household characteristics such as wealth and labour stocks have large and significant effects on both the diversity among and within cereal crops, varying among crops. Policies designed to encourage variety diversity in one cereal crop may have opposing effects in another crop. Trade-offs between development-related factors and diversity in this resource-poor system are not evident, however. Market-related variables and population density have ambiguous effects. Education positively influences cereal crop diversity. Growing modern varieties of maize or wheat does not detract from the richness or evenness of these cereals on household farms.

Introduction

In the less-favoured areas of the world where crop production is risky and opportunities are limited for insuring against risk through working off-farm, many farm families still depend directly on the diversity of their crops for the food and fodder they use. Crop biodiversity on farms¹ has both inter-specific (among crops) and infra-specific (within a crop) components (Bellon, 1996). The potential to secure harvests in some difficult growing environments is not the only economic issue motivating interest in crop diversity. Maintaining genetic variation in situ as a complementary strategy to conservation in gene banks has re-emerged as a scientific question (Maxted et al., 1997, Brush, 2000).

On-farm conservation of crop diversity poses obvious social, economic and policy challenges. In detailed case studies conducted in Peru (potato), Turkey (wheat), and Mexico (maize), applied economists have sought to identify the factors that affect the prospects that diversity is maintained on farms, while characterising those farmers most likely to continuing conserving it (Brush et al., 1992, Meng, 1997, Van Dusen, 2000, Smale et al., 2001).

Case studies have generally concluded that two major determinants of crop diversity at both the regional and farm level are agroecological heterogeneity and the extent of market development. Recently, however, the assumption that the opportunity costs of growing landraces rises with development and market integration has been challenged (Dyer, 2002). The impact of household characteristics such as human capital, assets and off-farm employment also appears to depend on the context. A negative relationship between modern varieties and crop genetic diversity is typically assumed, though empirical examples suggest that the relationship is more complex (Zimmerer, 1996, Brush et al., 1992).

We test related hypotheses in this paper. Comparing the determinants of inter- and infra- specific diversity among the cereals commonly grown in the highlands of Ethiopia, we highlight three types of policy trade-offs. First, the same policies may enhance the numbers or ‘richness’ of cereals and varieties grown but detract from the ‘evenness’ of their representation on farms. Second, to the extent that the determinants of diversity differ among crops, policies designed to enhance the diversity in one crop may have adverse consequences for the diversity of another crop. Finally, if modern varieties enhance diversity rather than detract from it in some environments, trade-offs between diversity and productivity may not be a policy concern.

The highlands of northern Ethiopia are a suitable empirical context for testing such hypotheses. Ethiopia is a centre of diversity for cereals such as barley, wheat, sorghum, finger millet and teff (Harlan, 1992). Often referred to as one of the eight Vavilovian gene centres of the world, Ethiopia has made a national commitment to conserve genetic resources on farms and in gene banks over the past two decades (Worede et al., 2000). The highlands of northern Ethiopia are relatively less favoured than other areas of the country in terms of both growing environment and market infrastructure, two of the generic factors hypothesized to positively affect crop diversity.

The conceptual framework for the analysis is presented next. The econometric approach follows, including the data, description of variables and related hypotheses. Findings are then presented in Section 4, followed by conclusions, implications and suggestions for further research in Section 5.