Why has Africa become a net food importer?

From the summary
That Africa has become a net importer of food and of agricultural products, despite its vast agricultural potential, is puzzling. Using data mainly for the period 1960-2007, this report seeks to explain Africa’s food-trade deficit since the mid-1970s. The core finding is that population growth, low and stagnating agricultural productivity, policy distortions, weak institutions and poor infrastructure are the main reasons..

WHY HAS AFRICA BECOME A NET FOOD IMPORTER?

Explaining Africa agricultural and food trade deficits, Manitra A. Rakotoarisoa, Massimo Iafrate, Marianna Paschali
trade and markets division, food and agriculture organization of the united nations, Rome, 2011

Full report from FAO

http://www.fao.org/docrep/015/i2497e/i2497e00.pdf