Four decades ago, Norman Borlaug, accepting the Nobel Peace Prize for his work on raising crop yields worldwide (the "green revolution"), said: "I have only bought you a 40-year breathing space to stabilise your population."
In 1970, when Mr Borlaug got his prize for postponing the onset of famine for 40 years, the world's population was 3.7 billion. Today, it is 7 billion. The United States Census Bureau expects only two billion more in the next 34 years, and we might actually stabilise the population by the end of the century - but we will have to feed almost three times as many people as there were in 1970.
How on earth can we do that?
Actually, you do not need to panic right away. The United Nations' Food and Agricultural Organisation (FAO) recently estimated that the extra people can be fed, at least until we hit 9 billion, if crop yields rise by 1% a year and the world's farmland expands by 13%.
There is enough potentially arable land for that, although it would involve cutting down the forests over an area the size of South Africa. Grain yields probably can go on rising at 1% a year if we manage irrigation and fertiliser use much better than we do now. And if the grain production expands, so does the meat production.
This takes no account of the ecological damage done by removing even more land from the natural cycles, and it omits details like the looming collapse of most of the world's big fisheries. Given the frequent forecasts of doom by over-population, however, it is a surprisingly reassuring assessment.
But this is a forecast that ignores the probable impacts of global warming on food production, and those will be dire.
In some places a hotter climate will actually increase food production, but in far more places crop yields will fall.
The rule of thumb is that we will lose 10% of global food production with every rise in average global temperature of 1degC. Since we are virtually bound to see an increase of 2deC before global average temperature stops rising (if it does), that is one-fifth of world food production gone.
It will be considerably worse in some places. In India, for example, a rise of 2degC means a 25% loss of food production. In China, it will probably be worse than that. And a crash in food production doesn't just bring hunger. It brings chaos: collapsing governments, waves of starving climate refugees crossing borders, even wars between countries that depend on the same river for irrigation water.
Military planners in many countries think that this may be the dominant factor in world politics in 25 years' time. That will make it even harder to get global agreement on measures to stop further warming, so they are making contingency plans for really ugly outcomes. But what if you could make food production independent of climate?
Specifically, what if you could make meat production independent of climate?
Do not use 70% of the world's agricultural land to grow grain that feeds the animals we then kill and eat.
Just grow the meat itself, taking stem cells from a cow, a sheep or a chicken and encouraging them to grow in a nutrient solution.
It is already being done in labs, but the quantities are small and the meat is still a long way from having the taste and texture that would make it a real candidate to replace meat from live animals. But those are details that can be sorted out with more research and more money. The point is that this could allow people to go on eating meat without trashing the climate in the process.
People are not going to stop eating meat: demand is going up, not down.
But if "cultured" meat can be made identical in taste and texture to "real" meat from animals, and if it can be grown in large quantities at a competitive cost, the ecological benefits would be immense. The political benefits might be even greater.
If half of the meat people eat was "cultured", greenhouse gas emissions would drop sharply (about one-fifth of global emissions from human sources come from meat production). About half the land that has been converted to grain-growing in the past century could be returned to natural forest cover. The famines and wars that would come with global food shortages could be postponed for decades, and even the warming itself might be stopped.
"Cultured" food may be commercially available in only a few years if the research is pushed hard.
Indeed, the animal welfare group Peta has offered a million-dollar prize for anybody who can demonstrate lab-made meat in commercial quantities by June 30 this year, and it thinks that one of the research teams now working on the problem may claim the award.
But it is not being pushed fast enough.
"There is very little funding," Prof Julie Gold, a biological physicist at Chalmers Technological University in Gothenburg, Sweden, told the Observer newspaper recently. "What it needs is a crazy rich person."
- Gwynne Dyer is an independent London journalist.
