Ecological surveys, conducted after a prolonged dry period (mean annual precipitation of 14 mm) and after a high rainfall event (118 mm), showed that the Namib dunes respond dramatically to rain. After rain the potential energy contained in the plant biomass increased ninefold while the potential energy in the detritus and the animal biomass increased sevenfold and sixfold, respectively. This sudden increase in biomass was largely due to the rapid growth of ephemeral grasses. The various habitats within the dune ecosystem differ markedly with respect to both productivity and stability. The dune slope is the most productive and the least stable, while the interdune valley is the most stable and the second most productive, in terms of contribution to the total biomass of the ecosystem. The most important limiting factors identified were water, and the nitrogen and phosphorus content of the dune sand as well as the physical stability of the sandy substrate in certain habitats. Keywords: Abiotic environment, Biotic environment, vegetation, fauna, interdune valleys, dune slope, plant excavation, food web, animals, energy, water and nitrogen cycle, nitrogen.