John Beddington, Britain's chief scientific adviser, had been in his job for just two months when he outlined an unnerving scenario for his new employers. The world, he argued earlier this month, faced an enormous problem - one on a par with climate change - that policymakers were nonetheless ignoring: food security.

As prices for agricultural commodities, from wheat to milk, have surged globally with unprecedented speed, social unrest and hunger have emerged in different parts of the world, challenging rich and poor countries alike and forcing governments to consider a variety of measures to bring prices down. Long subject only to the disciplines of the market, producers now increasingly find themselves contending with higher import tariffs, export bans and price freezes.