This thesis aims at an analysis of exogenous plant species’s proliferation phenomena, in the savannahs and gullys of the lower west of Reunion Island. In these environmental non-project spaces, the goal is to retrospectively understand and characterize the socio-ecological dynamics involved in the rapid transformation of landscapes : evolution of socio-spatial practices and representations, fragmentation and homogenization, landscape closure. The objective is also to highlight the processes that build environmental issues that public action could take over. The thesis defends a landscape entry, primarily cultural and social, into environmental processes and biodiversity. Based on an understanding of landscape processes by plants, this approach traces the landscape trajectory of the main invasive plant agent, Leucaena leucocephala. The thesis offers a new landscape narrative in which the proliferation of Leucaena leucocephala is the symptom of a profound change, both social and natural. It links the current invasive processes to a decline in the uses of plant species, itself a result of the erasure of marronnage local culture. The landscape approach permits to build a sensitive image of environmental realities, while highlighting the diversity of gazes on these realities. It makes extensive use of the image (photography, photo-comparison, video) in the field survey and in the restitution of materials. By giving visibility to unpublished "marronnes" practices, and placing the landscape at the crossroads of gazes, the thesis provides the materials for a mediation aims to found concerted action in the management of plant dynamics.