Research on the factors of plant diversity on the slopes of the Atacora Massif (Perma — Toucountouna sector) has been undertaken. The approach used includes documentary research, diachronic analysis of aerial photographs, ethnobotanical surveys, floristic inventory and data analysis. Phytosociological surveys were carried out according to the Braun-Blanquet method (1932) in circular plots with a radius of 20 m. In total, 127 surveys are carried out on the links and 247 species (woody and herbaceous) belonging to 180 genera grouped into 66 families are inventoried. The treatment of these surveys by Correspondence Analysis (CA) allowed the discrimination of 9 plant groups: these are the group with Ficus abutilifolia and Andropogon tectorum identified as soon as the rocky chaos leaves cracks; the grouping with Isoberlinia tomentosa and Andropogon tectorum located on the bottom of slopes with large denuded blocks with anfractuosities; the group with Detarium microcarpum and Hyparrhenia involucrata located on slopes with large denuded blocks with crevices; the grouping with Burkea africana and Loudetia flavida often disturbed by grazing; the grouping with Parinari curatellifolia and Hyparrhenia spp. localized on suboutcrop rocks; the grouping with Daniellia oliveri and Loudetia spp. ; the Vitellaria paradoxa and Andropogon gayanus group located on suboutcrop rocks; the group with Crossopteryx febrifuga and Cochlospermum planchonii more often observed on breastplate slabs with low permeability; the group with Pteleopsis suberosa and Loudetia flavida on armoured sandy-gravel soils with low floristic diversity. The basal area at the level of the studied links varies according to the topographic position, the nature of the geological substratum in place and the degree of anthropization of the various environments. It varies between 9.4 m²/ha and 13.2 m²/ha with an average of 11.3 m²/ha. The diameter of the tree at the average basal area also varies according to the topographic position. The average density for all formations combined is 393 stems/ha. This average is 665 stems/ha at the level of natural formations. Species richness varies from 10 to 97 species and decreases slightly from the bottom of the slope to the top of the slope and to the peaks. The same is true for the Shannon specific diversity index and Pielou equitability. They vary respectively from 2.3 to 3.7 bits and then from 0.7 to 0.9. The different richness values obtained as a function of the exposures are not significantly different based on the t-test. Statistical analysis of the illumination values obtained as a function of the East or West exposure did not reveal a significant difference. Moreover, there is a positive correlation between the richness of the surveys and the percentage of arable land. An average of 8.6 cm thick pre-soils erode each year in the Atacora mountains, which corresponds to 860 m3/ha of land loss. Analysis of aerial photographs from 1975, the vegetation map from 1994, and aerial photographs from 2003 showed that the wooded formations in the study area declined by 35%. The factors that contribute to the degradation of saxicolous forest formations are climatic, edaphic, topographic and anthropogenic. Among these factors, anthropogenic ones seem to be the most decisive. The local populations, after exhausting the wooded areas of the valleys, attacked the saxicolous formations. They thus destroy these environments, some of which fauna or flora species are threatened with extinction. The various links explored play very important ecological and socio-cultural roles in the field of study. It is urgent to think in the context of the sustainability of these ecosystems and therefore protect them from degradation, the effects and signs of which are obvious on the ground.