This article uses a CGE model to analyze the impacts of a possible downward trend of agricultural productivity in Burkina Faso. It also explores the impact of public investment in agriculture. The results shows the very high sensitivity of consumption levels of the poor to the level of agricultural productivity. While the current situation is already hard for rural as well as urban poor, a decline in agricultural productivity is likely to plunge them into an acute food shortage. In contrast, public investment in agriculture, through its positive impact on agricultural productivity is effective in the fight against poverty and food insecurity. Changes of agricultural productivity influence food consumption of the poor mainly through a strong variation in agricultural prices and real incomes.