I find cassava in the dry savannah lands. I know it is a south american plant but south america also has deserts. It might be in the rainforests as well.
From wikipedia: ""Cassava was introduced to Africa by Portuguese traders from Brazil in the 16th century. ... Cassava is one of the most drought-tolerant crops, can be successfully grown on marginal soils, and gives reasonable yields where many other crops do not grow well. Cassava is well adapted within latitudes 30° north and south of the equator, at elevations between sea level and 2,000 m (7,000 ft) above sea level, in equatorial temperatures, with rainfalls from 50 to 5,000 mm (2 to 200 in) annually, and to poor soils with a pH ranging from acidic to alkaline. These conditions are common in certain parts of Africa and South America. ""