A second food crisis in as many years is a wake-up call. At a meeting in the Italian town of L’Aquila last year, the leaders of the G8 pledged to enhance global food security to prevent a repetition of the 2007-08 shortages. Last week’s extension of Russia’s grain ban and eruption of food riots in Mozambique shows how much needs to be done to meet this goal.

The parallels with the last crisis should not be overstated. Despite the recent spike in wheat, food prices are still well below the peaks they reached in early 2008.

Nonetheless, once again, an initial spike in wheat prices, caused by adverse weather events, is pushing other commodities higher. The initial rise has then been exacerbated by export bans. True, only Russia has so far imposed a formal embargo. But there are informal restrictions on exports from Ukraine and Kazakhstan. These disrupt international markets and promote hoarding. While reserves are higher than two years ago, they are not sufficiently deep to absorb a serious supply shock.