The abiotic, or non-living, components of desert ecosystems include soil composition, annual precipitation, temperature and prevailing winds. These factors influence the biotic, or living, components of the ecosystems. For example, the scarcity of water causes plants to grow in depressions or sheltered areas that retain more moisture.
Aside from the paucity of rainfall – a defining factor of deserts – the average temperature is one of the most important abiotic factors affecting deserts. This is best illustrated by the differences in a given desert's native flora and fauna, depending on whether the desert is hot or cool. For example, Antarctica is a cold desert whose icy interior supports few animals aside from penguins. By contrast, the hot deserts of the Southwest United States and North Africa are home to a variety of invertebrates, reptiles, birds and mammals.
Soil chemistry strongly affects the plants that grow in various deserts, as does the average wind speed and direction. For example, if high, persistent winds blow across a sandy desert, dunes may form. Because they continually shift from one place to the next, plants cannot establish themselves in such regions.
Deserts usually have plenty of sun exposure – another abiotic factor that influences the lives of native plants – so evolutionary forces have concentrated on helping plants to obtain the scarcest resource in the habitat: water.