CAM features in a variety of different succulents in response to climatic changes between March 1977 and April 1981 were studied in the southern Namib desert (Richtersveld). In 1977 and 1978 all investigated succulents performed a CAM. After an extended period of insufficient rainfall which damaged the succulents between 80 and 100% most species did not show a measurable CO2 gas exchange or diurnal acid fluctuation, indicative of CAM. But both features were restored quickly after an abundant rainfall in March 1981. Artificially increased or decreased water stress confirmed that nocturnal CO2 uptake and malate accumulation is correlated with water supply and water content in the plant. The effects of the water status are overruled by rapid changes in the water vapour pressure deficit during the night. A sudden increase due to föhn-wind stopped or at least markedly diminished CO2 uptake and acid accumulation in CAM plants.