西アフリカにおける低湿地の土地所有制度と水管理技術への投資

抄録

This paper investigates empirically the determinants of the adoption of water control technologies for rice production, i.e. irrigation canals and bunds, in rainfed lowland in West Africa.Since the adoption of water control technologies is considered as medium- or long-term investment in land, land tenure security is hypothesized to have a significant influence on it. Our survey in 179 sample villages in Bouaké region, central Côte d'Ivoire, identifies two distinctive types of lowland ownership: family ownership and village ownership. Hence, the analysis focuses on the two types of lowland ownership. First, the factors that maintain village ownership are analyzed by a Probit regression using survey data from 242 lowlands in the sample villages.The main findings are that village ownership exists in lowlands easily monitored and that ethnically homogenous villages are more likely to have village-owned lowlands particularly if they have ethnic culture of community solidarity. On the other hand, population pressure and market access, which are suggested to be relevant by the induced institutional innovation theory, have no significant effect on the land ownership.Subsequent Probit regression analyses examine the effect of the village ownership on the adoption of water control technologies, where the village ownership is treated as endogenous.The results show that village ownership itself has no significant effect on cultivators' adoption of water control technologies. Rather it is significantly promoted by population pressure from immigrants and market accessibility, as predicted by the induced technological innovation theory. In addition, the results that immigrant population as well as education level enhance the adoption of canals but have no effect on the adoption of bunds suggest that canal technology may require more external intervention and cultivators' capacity of adoption. In conclusion, the improvement of market accessibility as well as extension systems will be required for the intensification of lowland rice production.