At least 1.5 million tons of crude oil has been split in the Niger Delta since 1958, according to the UN's Environment Program (UNEP).
Barrick Gold's boss navigates African disputes, settling Mali's $438m tax row amid rising resource nationalism.
Analysis - How the Libyan conflict transformed human trafficking routes in West Africa, and why Europe's response has so far failed.
Mahamoud Ali Youssouf inherits an office that has been charged with harbouring corruption, nepotism and cronyism.