Rising atmospheric CO/sub 2/ and crop productivity

The CO/sub 2/ level in the atmosphere is rising at the rate of 1.5 to 2 ppM per year. Although climatologists look to the rising level of atmospheric CO/sub 2/ as a problem of climate change, the effects on climate are uncertain. Biological effects are much more certain, predictable, and measurable. It can be assumed that CO/sub 2/ alters the heat balance of the earth and acts as a one-way screen, causing a ''greenhouse effect''. Both the climatic effects and the biological effects of rising atmospheric CO/sub 2/ are reviewed in depth. The most profound effect on crop productivity involves increased water-use efficiency and a reduction in the water requirement. Elevated levels of atmospheric CO/sub 2/ appear to have a remarkable positive effect on increasing the resilience of crops under environmental stresses.