A lack of economic diversification has long plagued much of Africa. During the colonial era and well beyond mono-crop agriculture did demonstrable harm to numerous societies. One of the destabilizing factors that fueled the conditions that created the Rwandan genocide, for example, was the collapse of coffee prices in a country dependent upon exporting coffee beans. Increasingly the mono-crop problem has been replaced with the so-called resource curse whereby countries discover oil, become dependent upon its export, warped by its allure, and disappointed by its false promises. The Brookings Institute has issued a report on Africa's diversification challenge, which you can, and should, access here.