Cattle herding allowed nomads to create livelihoods in an increasingly unpredictable and challenging environment, characterized by an arid climate and scarce resources. Today, there are some 50 million nomadic herders in Sub-Saharan Africa, and as many as 150 million agro-pastoralists, who combine traditional nomadic animal-rearing with some form of agriculture.
事实上，巨大的气候变化——将富饶绿色撒哈拉变成了荒芜的沙漠——在5000年前开启了东非的这一生活方式。放牧家畜让牧民得以在日益难以预测和具有挑战性的环境——气候干旱、资源匮乏——中创造生活。如今，撒哈拉以南非洲有大约5000万游牧民，和1.5亿农牧民，后者过着传统家畜放牧和某种形式的农业相结合的生活。