Extreme aridity and powerful winds characterise the Sahara Desert. Unprotected car windows become 'frosted' and car paint is quickly removed in such storms. Many locations experience an average annual rainfall below 25mm. Sand dunes move during violent storms and would be a huge threat if they reached farmers' fields. Deserts generally support a very sparse vegetation cover and this is certainly true of the Sahara.
Wild animals live off the meagre resources and have special mechanisms to conserve water.
Pastoralists use the desert where possible for grazing while isolated oases sustain date palms and other thirsty crops. These small pockets of human activity are minute compared to the vast expanse of the desert. The misconception that the Sahel is directly exposed to the Sahara has been widely accepted. The Sahara is sometimes pictured as a sea of sand dunes washing onto the Sahel exposing farmers to waves of sand that roll in from the desert, yearly swallowing large chunks of farming land. If true it would be understandable that projects plant green belts in order to defend the Sahel from the invasion.