Why did many tuareg settle on farms, move to cities, or build camps?

The reason why many Tuareg settle on farms, move to cities, or build camps is: Because of Droughts in Sahara.
In the end of 19th century, the area ear sahara region had to experience a massive drought known as the sahel drought which destroyed many major components of the region. In order to survive, the tuareg on farms, move to cities, or build camps near the region