Origins, Functions, and Persistence of Crop Biodiversity in the Betsileo

摘要

In order to assess Malagasy crop biodiversity (CB) richness and stability on a regional scale, an analysis at both species and variety levels was carried out in the Betsileo area of the Madagascar Highlands. The study zone was a transect between the humid forest zone and the drier savanna. Peasant agriculture is faced with the challenges of a fast-growing resident population, government development and forest conservation-based policies. Sampling was done at two scales: five villages and 45 farms representative of three main farm types (small and poor, medium-sized, and richer farms). Farm surveys were conducted to collect data on several aspects of CB: taxonomic richness, functions, origin, date of introduction, rarity, and threats. Forty-five species were recorded altogether. The number of species in each village varies from 27 (a forest village) to 41 (a savanna village). Sixteen species are omnipresent in the area: they constitute the common base of Betsileo agriculture. On the farm scale, species diversity is high everywhere: each farm grows half the species present in its village, but only several varieties thereof. Yet the six main species include 57 varieties in all, of which 46% are ancient and 76% are hardy landraces. The bigger farms grow significantly fewer varieties than smaller, poorer farms. Successful varietal introductions have not reduced local varietal diversity. Regional and local varietal richness of a species is closely linked to the number of varieties per farm, depending on local importance, ecological suitability, and risk management, and is increased by seed exchanges. Betsileo agriculture appears to be simultaneously dynamic and faithful to its risk strategies, way of life, and values, allowing conservation of its technical, genetic, and cognitive capital. Current individual practices of conservation of rare varieties through small collections and seed exchanges should be supplemented by collective actions