The present study investigates the physioIogical bases of species which compose the typical vegetation types of the Northern Namib: the savannas, the subtropical grasslands and the succulent deserts. The relative role in terms of vegetation cover and species diversity of the various pathways of photosynthetic production is determined and the environmental factors responsible for the distribution of the various metabolic types is discussed. Keyword(s) : Acid metabolism, Bundle sheath cells, C4 metabolism, CaIvin cycle, CAM, Chamaephytes, CO2-fixatio, Coastal fogs, Dewfalls, Hemicryptophytes, Hot dry climate, Morpho-genotype, Perennial phanerophytes, Photosynthetic production, Spatially separated mesophyll, Temperatures, Water stress.