Advice for those trying to solve the global food crisis: do not start from here. As governments across the developing world impose export bans on staple foods, further worsening the shortages on inter­national markets, the shortcomings of a system designed around the expectation of plenty are becoming painfully evident.

The causes are quite simple: principally higher demand from a richer world eating more protein and requiring more feedstock, and restricted supply because of variable weather and crops being diverted into biofuels.