We are five years into a severe global food crisis that is very unlikely to go away, says the well-known US fund manager Jeremy Grantham of GMO.

This developing problem is badly underestimated by almost everybody, he argues. It will threaten poor countries with increased malnutrition, starvation, even collapse. Resource squabbles and waves of food-induced migration will threaten global stability and global growth.

Paul Conway, vice-chairman of Cargill, the world's biggest agribusiness, says the world's hundred-year decline in food prices relative to personal incomes "is probably over."

Over the past decade the average price of food as measured by the United Nations has tripled. The poor feel the pain - Egyptians now have to spend 40 per cent of their income on food.

Although there are temporary factors that worsen the situation, such as the current drought in North America, the fundamental problem is that demand is growing faster than supply. Driving demand are three factors:

David Fuller's view I too am a Grantham fan. He is very successful, an original thinker and as nice a gent as one is likely to meet in the financial community. I regard his views as erring on the pessimistic side, and pessimists have had a good run in recent years.

Subscribers may recall that Fullermoney has often expressed concern about food supplies in recent years, not least regarding the dire consequences of shortages for poorer countries. However, I also maintain that the world is more than capable of feeding its expanding population, subject to weather developments.

Unfortunately, we cannot take generally benign growing conditions in the world's major agricultural regions for granted. In reality, we never could but global warming is a more recent and serious concern for anyone who is not in total denial. However, a warmer climate on average is far less of a threat to most agricultural crops than global cooling would be.