PhD Dissertation

Viability of Pentadesma butyracea Sabine populations and their socio-economics in Benin

Avocevou Carolle (2011)
PhD, University of Abomey-Calavi

NTFPs are a dependable source of income and food supply in the rural areas. They are obviously very important as they contribute to meeting food and other basic needs. They provide a source of input into the agricultural system, help households control exposure to risk of various kinds. The present study dealt with Pentadesma butyracea sustainable use through ecological, social and economic aspects. It aimed: (i) to model of the potential ecological niche of P. butyracea; (ii) to assess how the species use knowledge varies across different sociolinguistic groups; (iii) to determine the effects of fruit harvesting on population structure and on natural regeneration of P. butyracea and to estimate the net present value and the marketing margins of its fruits harvesting and almonds processing activities; (iv) to assess the impact of the species fruit harvesting intensity on its populations dynamics; (v) to identify and categorize actors that intervene in the species management; (vi) to search socio-economic and demographic factors that determine P. butyracea fruits harvesting by women. To model of the species potential ecological niche, 480 occurrence records of P. butyracea were georeferenced. Based on 19 environmental data layers (Worldclim version 1.3 at 1 km² grid resolution), predictions were generated using a modeling approach based on the principle of maximum entropy (Maxent). Considering the species probability of presence ≥ 20 %, P. butyracea potential ecological niche is mainly limited to the north-western part of Benin. The Jackknife analysis indicated that occurrence areas of P. butyracea are more characterized by water availability (combination of precipitation and temperature and precipitation variability).  We used four plant use indices to assess how the species use knowledge varies across different sociolinguistic groups from two geographical areas of Benin, and how these variations may influence the species’ conservation and utilisation strategies. Seven sociolinguistic groups namely the Anii, Nagot, Kotocoli, and Fulani in the central part, and the Waama, Ditamari and Natimba in the north-western part of the country were considered. We determined the reported use value of the plant parts, the plant part value, the specific use and the intraspecific use value for each sociolinguistic group. The various communities showed different interests in the plant organs they used. Nagot people showed the best plant use knowledge with the highest use value for bark and roots, two organs critical to the plant survival. Sociolinguistic groups living in the same geographical area shared similar plant part values, likely because of knowledge exchanges through social interactions. The class distribution in the low-intensity harvesting sites showed a typical inverse J-shaped curve whereas the high-intensity harvesting ones showed an almost bell curve (G² = 23.93 p = 0.0008). In order to assess the effects of fruit harvesting on natural regeneration of P. butyracea, we compared seedling and sapling density of regeneration originating from seeds and roots suckers in plots that had been differentiated according to fruit harvesting intensity. Observed seedling and sapling density was high (13,872 ± 7,886 seedlings and saplings/ha) in low-intensity harvesting sites but very low (4,200 ± 3,810 seedlings and saplings/ha) in high-intensity harvesting sites (F = 17.16; p = 0.0006). However, there was no significant difference between root sucker density in either the type of harvesting site (F = 0.79; p = 0.3861). Commercial margin analysis showed that these women involved in almonds and butter trade, far from being exploited by traders, recuperate between 49 and 80 % of the price paid by the consumer, depending on the quality of the product and the length of commercial channel used. A demographic study was implemented in stands submitted to low-intensity fruit harvesting and in stands submitted to high-intensity fruit harvesting. Demography data were collected during three years (2006 to 2008). A matrix model was constructed to characterize the populations’ dynamics of P. butyracea in the two fruit harvesting regimes. Contrary to stands submitted to high-intensity fruit harvesting where populations were declining (λ = 0.9444), Populations were increasing in stands submitted to low-intensity fruit harvesting (λ = 1.0025). Elasticity analysis of λ to changes in reproduction, survival and growth of P. butyracea indicated low contributions to λ of growth and reproduction elements, suggesting that the harvesting of fruits have a low impact on P. butyracea population dynamics. Differences in populations dynamics between the two fruit harvesting regimes were then explained by other disturbances (bush fires, felling of adult P. butyracea trees for timber, land clearing in riparian forest for agriculture, etc.). A stakeholder analysis was used to characterize the social context of P. butyracea natural stands management. P. butyracea was a resource that property rights were not well specified. According to the degree of destruction their activities have on the species viability, stakeholders were dispatch up into three categories. There was convergence of interests between actors belonging to the same category whereas conflicts were noticed between those who were in different categories. The forestry sector is increasingly understanding as a key element in poverty reduction strategies in Africa. Understanding the factors influencing access to products from commonly-owned forest resources could form the basis for developing, modifying and targeting policy instruments that promote equitable access. A logistic regression model linking women and their household’s socio-economic and demographic characteristics and their P. butyracea fruits collection patterns was examined. The results showed that P. butyracea fruits collection is associated with household low wealth and Vitellaria paradoxa kernels collection. P. butyracea fruits collection was also influenced by proximity to riparian forests (natural stands of the species in Benin) and house enclosure.

Key-words: ecological niche modeling, quantitative ethnobotany, fruit harvesting impact, stakeholders, socio-economic determinants.