By mobilising palaeoenvironmental and palaeoclimatic methods (isotope geochemistry) as well as a mechanistic model, the aim of this thesis is to compare records of changes during the recent Holocene in vegetation, fire and relative atmospheric humidity obtained from cored lake sediments in West and Central Africa. This multi-proxy approach with high temporal resolution will allow to exploit different indicators to provide new information on the vegetation and climatic changes that have taken place, and thus shed light on the ongoing debate on the respective implications of human and climate on the opening of the African rainforest during the recent Holocene (~2000 years BP). This research will also provide new information on the variables responsible for transitions between tropical forests and savannas in the context of Alternative Steady States and improvements to the LPJ-GUESS vegetation model. More accurate projections of the future state of forests and savannas can be made. These are necessary in order to provide more appropriate solutions for the conservation of these ecosystems. The results will be interpreted in the light of knowledge about the ecological functioning of these biomes.