World population growth
Increased demand for more resource intensive food
Effects of petroleum and fertilizer price increases
Declining world food stockpiles
Financial speculation
Commodity index funds
Effects of trade liberalization
Effects of food for fuel
Biofuel subsidies in the US and the EU
Idled farmland
Agricultural subsidies
Distorted global rice market
Crop shortfalls from natural disasters
Soil and productivity losses
Rising levels of ozone
Unrest and government actions in individual countries and regions
2013 research concluded that the spike was the result of an unusual combination of circumstances and prices in the future will be higher than before the spike, depending on oil prices, climate change, and future diets.
https://en.wikipedia.org/wiki/2007–08_world_food_price_crisis