As the African Cultural Center observes, West Africa is a diverse region. Stretching from the dry Sahara Desert in the north to lush rain forests in the south, its physical geography includes numerous different environments. Generally, from north to south the dominant conditions change from desert, to semi-desert, to steppe, to savanna grassland, to deciduous forest, to tropical rain forest. This is mainly due to climatic variations; the north tends to be hotter and drier, becoming gradually wetter as you move south.