Arid and semi-arid regions covering more than 40% of the earth surface. Extreme climate conditions are characteristic for these regions. Under such harsh environmental conditions a special adapted flora and fauna have developed. These fragile ecosystems are endangered by climate change and desertification. Therefore, understanding of ecological processes in time and space is important for a sustainable land-use and the protection of biodiversity. Investigations of ecophysiological adaptations of desert plants were carried out in the Succulent Karoo, Namib, Negev and Sahara.