The Sahara desert is the largest hot desert in the world, covering around 8.5 million square kilometers across 11 countries in North Africa. It has an extremely hot and dry climate with some of the highest recorded temperatures on Earth. While the Sahara was once a fertile region, over thousands of years natural forces and human activities have converted it into a largely barren wasteland of sand that is unsuitable for most plant growth except for some hardy species like cacti and acacia. A few oases located among the desert support settled populations that farm dates and engage in herding and trade.