From Wikipedia
On 31 March 2008, Senegal saw riots in response to the rise in the price of food and fuel. Twenty four people were arrested and detained in a response which one local human rights group claimed included "torture" and other "unspeakable acts" on the part of the security forces. Further protests took place in Dakar on 26 April 2008.
The years 2007–2008 saw dramatic increases in world food prices, creating a global crisis and causing political and economical instability and social unrest in both poor and developed nations.
Systemic causes for the worldwide increases in food prices continue to be the subject of debate. Initial causes of the late 2006 price spikes included droughts in grain-producing nations and rising oil prices. Oil price increases also caused general escalations the costs of fertilizers, food transportation, and industrial agriculture. Root causes may be the increasing use of biofuels in developed countries (see also food vs fuel), and an increasing demand for a more varied diet across the expanding middle-class populations of Asia. These factors, coupled with falling world-food stockpiles all contributed to the world-wide rise in food prices. Causes not commonly attributed by mainstream views include structural changes in trade and agricultural production, agricultural price supports and subsidies in developed nations, diversions of food commodities to high input foods and fuel, commodity market speculation, and climate change.