The contribution of non-timber forest products (NTFPs) to rural household revenues in two villages in southeastern Burkina Faso.

Questions: West African savanna ecosystems are affected by increasing land use intensity (e.g., agriculture and livestock herds) due to a growing human population. To understand the impact of land use intensification on savanna vegetation, we aim to answer the following questions: How do savanna species composition, diversity and structure change with increasing land use pressure? Are the impacts of land use change different in the woody and the herbaceous layers? Do the effects of land use change differ between vegetation types? Location: Southeastern Burkina Faso, West Africa. Methods: Vegetation plots from the early 1990s representing vegetation types occurring in fallows of different age and in uncultivated pasturing zones were resurveyed. We distinguished between woody (tree and shrub layer) and herbaceous vegetation types. Species composition changes were analyzed using ordination techniques (detrended correspondence analysis, DCA) and indicator species analysis (IndVal). Species turnover and plant diversity as represented by species richness and evenness were compared between the baseline survey and the resurvey. Results:In most woody vegetation types, we found no change in species composition and richness over the past two decades. However, some highly valued woody species decreased in abundance. In contrast, in most herbaceous vegetation types, species composition changed considerably and species richness increased. The proportion of wide-ranging, ruderal herbaceous species increased, indicating a homogenization of herbaceous vegetation types, while preferred fodder herbaceous species decreased. We assume that the increased grazing intensity over the past two decades is the driver of these changes in the herbaceous layer. Conclusions:Our results show different reactions of vegetation types and layers to land use intensification and reinforce the need for studies on the basis of vegetation type that incorporate both the herbaceous and the woody layers.

Wild plant species are important nutritious supplements to otherwise nutrient poor diets of rural populations in West Africa. Consequently, a decline of wild food species has a direct negative impact on the nutritional status of local households. In this study, we firstly investigated the preferred wild food species in south-east Burkina Faso, their perceived change in abundance as well as their contribution to wild food income. Secondly, we studied how these species might be substituted in times of species shortfall. Thirdly, we investigated the impact of socio-economic variables on the substitution choice. We conducted 155 household interviews in two villages and found 21 wild food species. With a contribution of almost 70% to wild food income, Vitellaria paradoxa and Parkia biglobosa were economically most important. All species were considered declining to some degree. The wide range of cited substitutes for the ten most important wild food species indicates a great knowledge on alternative plant species in the area. For the majority, the substitution choice did not depend on socio-economic characteristics. Cited as surrogate for several important wild food species, the native tree Balanites aegyptiaca was the most important substitute species. Many valued wild food species were substituted with other highly valued wild food species and therefore the decline of one species can lead to a shortfall of another substitute. Thus, even though our results suggest that people are able to counteract the decrease or absence of wild food species, growing decline of one species would concurrently increase the pressure on other native food species.

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West African savannas undergo severe changes due to climate change and land use pressure, resulting in degradation and biodiversity loss. These changes directly impact local rural livelihoods, as many cash poor rural communities depend on the provisioning ecosystem services of their environments. In a case study of the interdisciplinary research project UNDESERT, the increasingly challenging sustainable use of wild plant species in West African savannas was investigated. In this study, we present the results and give examples of how scientific results can serve for practical actions to foster sustainable use of important plant resources.