The second war was partially about natural resources. Between the north and the south lie significant oil fields and thus significant foreign interests (the oil revenue is privatized to Western interests as in Nigeria). The north wanted to control these resources because they are situated on the edge of the Sahara desert, which is unsuitable for agricultural development. Oil revenues make up about 70% of Sudan's export earnings, and contribute to the development of the country which, unlike the south, does not depend on international aid. Due to numerous tributaries of the Nile river and heavier precipitation in the south of Sudan they have superior water access and fertile land.