Part of French West Africa until independence in 1960, Mauritania is influenced by Arab as well as African cultures. Crop growing is largely confined to the floodplain of the Sénégal River, straining relations with the country of Senegal over use of the river. Some of the world's richest fishing grounds lie off the coast. The population still largely depends on agriculture and livestock for their livelihood, even though recurring droughts forced most nomads and many subsistence farmers into the cities. The country has been further strained by internal racial divisions between blacks and Arabs.