Recent advances in autecology and plant physiology on the effects of aridity stress conditions on the micro-morphology of plant epidermal short-cell silica bodies (phytoliths) provide a new tool for evaluating subtle change in precipitation. An ongoing, integrated project concerning the modern phytoliths/vegetation/climate relationships of the Namibian area is outlined. The photosynthetic pathway appears to be the major factor determining how successful plant species are under different climates. Contemporary grass phytoliths clearly illustrate how the chorology of species with C3 or C4 photosynthetic pathways depends on the mean annual rainfall. The photosynthetic pathway of grass species can be determined by examining the shape of the silica bodies formed in the short-cells of the grass leaf epidermis. The differences in these shapes can be used to show how the relative abundance of species varies with the annual rainfall. Therefore modern grass leaf phytoliths are physiologically informative, and can easily be distinguished from those of other parts of the plant (and from non-grasses). It is demonstrated that African grass phytoliths have to be used as a proxy for aridity to improve the resolution of fossil records, in that changes in the total phytolith assemblages provide information about phytoclimatic shifts of the deciduous open vegetation in response to past rainfall events. Phytoliths offer a powerful addition to conventional palynology in arid areas. Since their biogenic signal can also be recovered from sediments, this approach: (1) can contribute to explain the functional patterns of the past vegetation, and (2) can help to predict future trends of the biomes of arid lands. Keywords: C4 (four-carbon chain fixation), K (Kranz anatomy), me (malate enzyme), NAD (nicotinamideadeninedinucleotide), NADP (nicotinamideadeninedinucleotidephosphate), PCK (phosphoenolpyruvatecarboxykinase), Okavango, silica bodies, annual rainfall, vegetation biomes.