Plant diversity management in cocoa agroforestry systems in West and Central Africa-effects of markets and household needs

摘要

Cocoa production in humid forest landscapes has been one of the main cash providers of West and Central African economies. Along with the liberalization of the perennial tree sector, there are increased fluctuations of cocoa income. At the same time, the demand and interest for timber production and non-wood forest products have also been increasing. With the continuous disappearance of natural forests, the production of these commodities is being shifted into cocoa agroforests and plantations. In view of helping research and development institutions in promoting sustainable tree crop systems, this paper attempts, for the main cocoa producing countries of West Africa (Cameroon, Nigeria, Ghana and Cote d'Ivoire), to: (1) document the temporal evolution of the market demand for forests and non-wood forest products both at the local and international levels; (2) explore the set of tree species that can be produced in cocoa agroforests of WCA to satisfy this demand. Deforestation resulting partly from the expansion of perennial orchards and slash and burn agriculture is: (i) leading to a shortage of suitable forest land necessary to stabilize or increase national cocoa production and (ii) increasing the gap between the demand and availability/supply of non-wood forest products(NWFP) and timber by reducing the main source of these products-the forest. Demand of these products is increasing with the growth of urban and peri-urban centers. At the same time, perennial agroforestry systems such as cocoa agroforest are increasingly perceived as assets for Payment for Environmental Services (PES) such as carbon storage and biodiversity conservation, because of the potential of the resources that they can generate. These demands of products and payment for ecosystem services that can be provided by sustainable cocoa agroforestry systems depends upon the appropriate combination of cocoa, timber and non-timber forest trees on the same land. Such demands is still to be properly exploited in the region. Cocoa agroforests in West Africa are characterized by fewer species than those of Central Africa. The level of market access influences the types of species that are managed inside cocoa agroforests. Among the species potentially associable with cocoa, those demanded by the local, regional and international markets are not necessarily the ones that are more frequent in the cocoa fields. The gradual reduction of natural forest, from which timber and non-timber products are gathered, aroused the need to integrate the growing of such species in cocoa agroforestry systems.