Rising food prices are a threat to many; they also present the world with an enormous opportunity. For as long as most people can remember, food has been getting cheaper and farming has been in decline. In 1974-2005 food prices on world markets fell by three-quarters in real terms. Food today is so cheap that the West is battling gluttony even as it scrapes piles of half-eaten leftovers into the bin. That is why this year’s price rise has been so extraordinary. Since the spring, wheat prices have doubled.