Roger Bannister did something that the experts considered impossible -- he ran a mile in under four minutes in 1954. Notice how no one is talking about a three-minute mile more than 50 years later? The same analogy helps explain why there may not be a second Green Revolution when the global population is expected to keep rising.
An excerpt from the March 29 BBC story by Mark Doyle:
In Punjab, I was looking for clues about whether output could be boosted further to cope with the rising demand that will be required to feed a world population set to rise from 6.6 billion today to more than nine billion people by 2050.
Food output across the world increased considerably in the last four decades of the 20th Century, largely as a result of the intensive farming techniques introduced by the Green Revolution.
The new techniques involved distributing hybrid grain seeds - mainly wheat, rice and corn. The hybrids grow with a shorter stalk. This maximises the process of photosynthesis, which nourishes the grain because less energy goes into the stem.
The hybrid seeds were combined with the intensive use of fertilisers and irrigation.
Population v Production
After successfully being introduced in India, the Green Revolution was rolled out in other parts of Asia, Latin America and the Middle East. It was so successful in terms of production increases that it defied the gloomy Malthusian predictions of the 1960s, which said hundreds of millions would starve as population outstripped farm output.
The Revolution was a technological success.
"Before the 1960s, the population of India was multiplying like rats in a barn," said Jagjit Singh Hara, "but we didn't have the grain to feed them. After the Green Revolution, we doubled our yield and now we have proved that India can feed the world".
But the process has limits and they may have been reached. Population, on the other hand, has continued to rise in poor parts of the world.
The graph, compiled for the BBC by the UN Food and Agriculture Organization, shows that while yield per hectare has increased, the amount of land used for the major staple grains has remained fairly constant; this is because the amount of good farmland is finite.
Given the shortage of land suitable for growing more food, the obvious answer would be a new Green Revolution, or another hike in yields. But this may not be possible.
"The difficulty is that we are now pressing against the photosynthetic limits of plants," says the influential environmentalist Lester Brown of the Earth Policy Institute in the United States.