Issouf Bamba

Fragmentation of Forest Landscapes in Central Africa: Causes, Consequences and Management

Forest fragmentation has a paramount impact on landscape pattern and has therefore been a key focus of landscape ecology. Trends and causes of deforestation are analysed for the Democratic Republic of the Congo, Rwanda and Burundi, and are put in a regional, continental and global perspective. In order to investigate the role of shifting cultivation as a driver of fragmentation, the dynamics of a forest landscape between 1970 and 2005 for a study area in the Bas-Congo province of the Democratic Republic of the Congo were analysed. Using a transition matrix and the identification of the spatial land transformation processes involved, historical data are compared with the current situation based upon field visits and remote sensing imagery. As a consequence of non sustainable shifting agriculture, forest fragmentation is observed, leading to an expansion of savannah, fallow lands and fields which replace secondary forest vegetation and limit forest succession towards primary forest. Since forest ecosystems are known to be the habitat of indicator species only observed in one specific phytogeographic territory, the potential impact of habitat preservation for these species is investigated. A dataset of 310 Acanthaceae species containing 6362 herbarium samples for the Democratic Republic of the Congo, Rwanda and Burundi is analysed and species presence is compared with the phytogeographic theories of Robyns (1948), White (1979,1983) and Ndjele (1988). Study of the spatial distribution and analyses of species habitats reveal the importance of forest preservation to protect these indicator species. Conservation of these habitats should therefore be given priority to avoid loss of genetic resources for future generations. Implications for the management of forested landscapes are discussed, regarding the role of local populations, the application of ecological principles, the conservation of virgin forests, the potential role of forest plantations, and the importance of landscape pattern analysis.

Forest fragmentation: causes, ecological impacts and implications for landscape management

In order to enable the development of appropriate landscape management plans, the causes and impacts of fragmentation should be fully understood. A new definition, incorporating the key aspects cited in landscape ecological literature since the 1980s, is proposed in order to shed light on the matter of fragmentation. By means of two case studies in the Democratic Republic of the Congo (Oriental Province) and in North Benin, the key role of anthropogenic activities in landscape fragmentation is evidenced; the spatial dispersion of forest vegetation is linked to population density and land use change. The potential impact of fragmentation on biodiversity is shown by an analysis of forest diversity in Ivory Coast (Tanda region), and by a study of edge effects on two rodent species in the Democratic Republic of the Congo (Kisangani). The chapter is concluded by an study on how planned corridors, assuming a spatial regrouping of existing teak plantations, could contribute to the conservation and management of remaining natural forest patches in the Atlantic Department in Benin.

A Methodological Framework to Quantify Anthropogenic Effects on Landscape Patterns

From an ecological landscape perspective, cultural landscapes can be considered as “anthropized” landscapes, in which patterns and processes are altered by human intervention. The importance of the study of spatial patterns in landscapes is justified by the pattern/process paradigm. The emergent properties of patterns reflect two components: landscape composition, which describes the number of patch types as well as their abundance, and landscape configuration, which refers to the spatial arrangement of the patch types. In this chapter, methods and strategies to analyze spatial pattern and landscape dynamics are discussed, and emphasis is put on the detection and quantification of anthropogenic effects on landscapes. Land mosaics showing anthropogenic effects are characterized by fragmented natural land cover, high frequencies of edge habitat, simple patch geometry, and dominant proportions of anthropogenic patch types. Landscape transformations associated with “anthropization” lead to a disintegration of natural patch types and to a reinforcement of anthropogenic ones. Four techniques to measure anthropogenic effects on pattern are discussed (1) the quantification of the fragmentation of natural habitats and its interpretation in terms of diversity, heterogeneity and entropy, (2) the quantification of edge effects in order to measure the ecological impact of human activity, (3) the determination of patch fractal dimensions to detect pattern simplification, and (4) the determination of the landscape transformation processes responsible for pattern dynamics. At the end of the chapter, a short list of analysis methods and strategies is proposed for detecting and measuring landscape “anthropization.”

Assessment of schistosomiasis and intestinal helminths following mass drug administration in the Centre and Plateau Central regions of Burkina Faso

Schistosomiasis is the most important waterborne disease in Sub-Saharan Africa. Transmission is governed by the spatial distribution of specific freshwater snails that act as intermediate hosts and human water contact patterns. In developing countries, such as Burkina Faso it remains a serious health problem, which management face important gaps. The main of theses gaps is the lack of reliable information about prevalence. Then, this study has been undertaken in order to determine the prevalence of schistosomiasis in the Centre and Plateau Central regions in Burkina Faso. A cross-sectional descriptive study was conducted in the Plateau Central and Centre regions of Burkina Faso to assess the status of schistosomiasis and intestinal worms among school age children. 1,455 school-age children were selected to participate to the study. Results shows that prevalence of Schistosoma haematobium in the Plateau Central and Centre regions were 4% and 0.6% respectively, with an overall prevalence of 2.3% (95% CI: 1.5% - 3.1%) in two regions. The following intestinal parasites were found in stools with various prevalence: Schistosoma mansoni 0.1% (95% CI: 0% - 0.3%) and Ancylostoma duodenale 0.1% (95% CI: 0% - 0.2%). The prevalence of urinary schistosomiasis in the Centre and Plateau Central regions had been greatly reduced from the previous level in the published data since the large-scale population treatment initiated in 2004. The study confirmed the success in controlling the disease by preventive chemotherapy. However, the progress toward its elimination requires that the implementation of a monitoring and evaluation system focused on sentinel sites, and aiming at quantifying the impact of treatment, be gradually coupled with a monitoring system to identify any outbreak of residual transmission.