The price of chocolate is soaring this Easter as demand outstrips supply due to poor weather conditions in the tropics and increasing crop blight.
The shortage has been compounded by a significant rise in demand among the growing middle classes in China and India.
An extra million tons of cocoa will be required to meet demand by the end of the decade - equivalent to the entire output of the Ivory Coast, the world's biggest producer, according to estimates.
The amount of suitable land in major cocoa-growing regions is expected to halve by 2050 due to global warming, according to research by the Bill and Melinda Gates Foundation.
"Supply just can't keep up with demand for long," said the Organic Consumers Association charity.
Cocoa trees, which bear fruit only in the tropics, take years to mature, and are vulnerable to diseases such as Witches Broom and Frosty Pod Rot, which caused up to $750 million in damage last year.
Scientists have now decoded the genome of cocoa, and plan to create a genetically modified version of the plant that is more resistant to disease.
But manufacturers in West Africa, which produces 70 percent of the world's cocoa, are turning away from cultivation of the crop. They complain that the price of cocoa is volatile, farms are too small to be economical, yields have not risen in decades, and alternative crops such as rubber are more lucrative.
"Everybody is worried that the farmer is living on the edge of poverty," said Barry Parkin, the head of global procurement and sustainability at Mars, whose products include the bestselling US brand M&M's.
"They produce half a ton per hectare of cocoa, and it has been that way forever. All major agricultural products have improved their yields by a factor of 5 to 10 in the last 50 years, and cocoa hasn't."
Demand will outpace production by 1 million tons by the end of the decade, said Parkin.
The chocolate market expands by 2-3 percent a year, according to Zurich-based Barry Callebaut, the world's biggest maker of bulk chocolate.
Supply has fallen short of demand in 10 of the past 20 years, according to the International Cocoa Organization in London. The ICCO forecasts a shortfall of about 50,000 tons for this season, which began in October.