In Tunisia, operations to dismantle migrant camps in the olive groves of Sfax, in the east of the country, have been gathering pace since April. According to National Guard figures, between 20,000 and 30,000 migrants from sub-Saharan Africa had been living in these makeshift camps. But is this strategy effective, and at what human cost? Our correspondents Lilia Blaise and Hamdi Tlili report.