How the World Really Works: A Scientist’s Guide to Our Past, Present and Future

by Vaclav Smil

A warmer atmosphere will also enhance water loss from plants (evapotranspiration), but that does not mean that crops and forests will wilt as they lose water. A rising atmospheric level of CO2 means that the water required per unit of yield will decrease in a warmer and CO2-richer biosphere. This effect has already been measured in some crops, and wheat and rice (staple grains which rely on the most common photosynthetic pathway) will increase their water use efficiency more than corn or sugar cane (which use a less common, but inherently more efficient, pathway).68 This means that, in some regions, wheat and other crops could yield as much or more than today, even if the precipitation they receive is reduced by 10–20 percent.