Sean O'Grady: What is good news for hungry people may not be good news for the planet

Few technological leaps forward are unalloyed good news in economic terms, and so it is with the decoding of the wheat genome.

Its unlocking will certainly boost agricultural productivity, make food cheaper and allow mankind to once again escape (for the time being) the fate predicted for it so famously by Thomas Malthus in 1798: that the tendency of the population to increase faster than the supply of food will lead to mass starvation. Even in his time that was becoming outdated, thanks to enclosure, crop rotation and selective breeding. The green revolutions in India in the 1960s and elsewhere showed that boosting production is possible across the globe.

The downside is the fact that, while we could feed a bigger world, our world isn't getting any bigger, and more humans means more global warming, and cheaper wheat means cheaper animal feedstuffs. As China, India, Indonesia, Brazil and other populous, fast-moving economies grow more prosperous, their peoples switch to eating pork, cattle and poultry – both inefficient and climate-threatening trends.

It may be that green technology will allow us to support hundreds of millions more humans with no adv-erse consequences, but that is far from a given. If the burgeoning populations of the emerging world want the same standard of living as Americans enjoy today we would need several more planet Earths, even on a very optimistic view of what technology can do for us. The limits to economic growth aren't techn-ological; they are environmental.