As the U.S. and the world braced themselves for the results of one of the most polarising and tense presidential campaigns in recent history last fall, many Californians were focused on a ballot measure that had become as hotly disputed in the final months of the election as the presidency itself.

Proposition 37 proposed the labelling of foods made from genetically modified (GM) or genetically engineered (GE) crops – crops produced from seeds whose DNA has been altered to enhance desired traits, such as resistance to herbicides. Critics have long claimed that the health risks associated with such foods have never been properly assessed and raise concerns over environmental impacts, including the emergence of new “super” weeds resistant to herbicides.

Proponents of the ballot measure argued that Californians had the right to know what was in their food; opponents countered that such a move would result in a hike in food prices as new labelling costs were passed on to consumers.

Polls showed overwhelming support for “Prop 37″ as late as September, with some results putting “Yes” support at over 75 percent – not surprising perhaps for a state that has been at the forefront of the local food movement in North America since before it could be considered a movement. But California wasn’t alone. In independent surveys conducted across the country over the past 10 years, Americans have consistently shown close to 90 percent support for labelling of foods containing genetically modified organisms (GMOs).

By early October, however, the margins had narrowed considerably. A flood of ads from the “‘No’ on 37″ campaign, financed by agro-chemical giants such as Monsanto, Dupont, Kraft, and Coca Cola pummelled the “Right to Know” forces, as doctors reassured voters there was nothing scary about GMOs. In the end, the “No” campaign’s US$46 million push was decisive. Outspent by 5 to 1, the yes side lost the ballot measure by a slim margin: 53-47 percent.

The staggering sums invested by the agro-chemical industry in the debate should not be surprising in what is turning out to be an historic battle. The U.S. remains one of the few industrialised countries that does not impose mandatory labelling of GMOs; 61 other countries, such as France, Russia, Brazil and Japan, already have similar legislation. A victory in California would have opened the floodgates for other states as well – and indeed the world – with obvious consequences for the corporate food industry.

But biotech’s fight against transparency is nothing new…