Timbuktu has long been a crossroads of north and sub-Saharan Africa, but its mayor fears its cosmopolitan identity is at risk as light-skinned residents flee reprisals after a 10-month occupation by Islamists. The fabled caravan city rose to fame in the 14th century as a trading hub where Arabs and Tuaregs exchanged northern salt for southern gold transported by black Africans to the edge of the Sahara.