The forests of the Congo Basin are among the world’s best preserved forest areas. However, the factors driving deforestation elsewhere in the world are also evident in this sub-region of the world. The theory of forest transition describes how the trend of declining forest land at national level can precede an increase in forest areas. While the effects of the forest transition are known in terms of forest cover degradation, there is little information on the effects of the forest transition on socio-ecosystems (SES) (understood as a group of particular actors with impacts on a particular resource group and subject to particular institutions). The general objective of this thesis is to characterise the transformation of the SES in the Congo Basin in order to define the dynamics of the evolution of the forest SES in the Congo Basin and their possible future. The socio-economic data collections, covering the description of the population, the various activities and income generated, the food bol and the modes of access to resource spacing were carried out in three SCEs with a mixed gradient of forest cover, located in Cameroon and Gabon. The results show that the cost price of meals increases overall with the decrease in forest cover. The share of food cattle linked to the exploitation of natural resources such as hunting, fishing and harvesting decreases in favour of protein from livestock production and agricultural commodities. This leads to a translocation of demand but also pressures on other anthropogenic ecosystems. The effects of deforestation are then felt at local level but also on neighbouring countries. The diversity of game is decreasing and prey is evolving towards smaller species as the forest transition is progressing. As a result, there is a reduction in the proportion of these products in both household food and income and a decrease in the importance of non-wood forest products (PFNL) in village production and livelihoods. Itinerant burning farming is practised in the 3 SES. While the proportion between the length of set-aside practised and the duration of cultivation decreases with the forestry transition, there is an increase in crop diversification leading to food diversification. Access to forest resources, agricultural land, markets and an external source of employment is a condition for village activities. Land management enables the levels of ownership and co-management of customary space to be reported. As the forest transition curve progresses, land management changes from relatively collective and informal ownership to privatisation and the availability of resources. These important changes in traditional systems for regulating relations between man and land lead to a more adequate management of certain commercially valuable resources (such as agricultural foodstuffs or mineral resources). On the other hand, this process is not compatible with the maintenance of certain ecosystem services such as the conservation of populations of large fauna. While these different results fit relatively well with the forest transition curve, this is not the case for all SCEs in Central Africa. We therefore propose combining some of the results achieved to reflect a well-known change in the qualities of a socio-ecosystem, regardless of the level of forest cover. The priority would be to establish a standardised data collection protocol to test sites with forest cover and localised on the different trajectories. The use of a socio-economic index would make it possible to predict the evolution of SES subject to different scenarios, whether linked to global or regional pressures (such as the emergence plans issued by the Central African States) or in contexts of economic crisis or the introduction of new legislation.