Taylor: How the rising price of corn made Mexicans take to streets

Thousands of people were marching on the main cities calling on their pro-free trade businessman President to halt a phenomenon threatening the lives of millions of Mexicans.

In their hands the protesters clutched cobs of corn, the staple crop that makes tortillas and for many of Mexico 's poor the main source of calorific sustenance in an otherwise nutritionally sparse diet.

Over the past three months the price of corn flour had risen by 400 per cent. Despite being the world's fourth largest corn producer and a major importer of supposedly cheap American corn, millions of Mexicans found the one source of cheap nutrition available to them was suddenly out of reach.

Poor Mexicans, who normally expect to set aside a third of their wages for corn flour, had always been particularly vulnerable to price fluctuations in the corn market, but a four-fold increase was both unheard of and potentially catastrophic.

The reason for such a substantial increase in the price lay north of the border. In order to wean itself off its addiction to oil, the US was turning to biofuels made from industrial corn like never before. Farmers in Mexico and America had been replacing edible corn crops with industrial corn that could then be processed into biofuels, leading to a decrease in the amount corn available on the open market.