A principal driver of food scarcity will be global population growth, particularly in the developing world. The global population has doubled since 1970, and is projected to reach 9 billion. One thing investors have been looking towards is the price of oil, which is closely correlated with food prices. That results from the energy and fertilizer costs associated with modern agriculture, and increasing demand for biofuels as oil prices rise.
Nomura, Global Economics and Strategy (2010) "The coming surge in food prices"