Background
There is growing concern that it will be difficult to feed the expanding human population of the planet just a few decades from now without the taking of great quantities of land (Waggoner, 1995; Tilman et al., 2001, 2002; Huang et al., 2002) and nearly all available freshwater resources (Wallace, 2000) from what might be called "wild nature," which habitat usurpation could lead to the extinction of far greater numbers of plant and animal species (Raven, 2002) than what climate alarmists are predicting will be caused by global warming. Idso and Idso (2000) have described how the aerial fertilization effect of the ongoing rise in the atmosphere's CO2 concentration can boost the yields of current crop varieties and help avert this disaster, as we discuss in more detail in our Editorial of 4 Sep 2002. The most recent work of De Costa et al. suggests an additional way of profiting from the expected increase in the air's CO2 content and its ability to stimulate agricultural productivity and water use efficiency.

What was done
The authors grew 16 genotypes of rice (Oryza sativa L.) under standard lowland paddy culture with adequate water and nutrients at the Rice Research and Development Institute in Sri Lanka from May to August (the yala season) and from November to March (the maha season) within open-top chambers maintained at either the ambient atmospheric CO2 concentration (370 ppm) or at an elevated CO2 concentration (570 ppm).

What was learned
De Costa et al. report that the CO2-induced enhancement of the light-saturated net photosynthetic rates of the 16 different genotypes during the grain-filling period of growth ranged from +2% to +185% in the yala season and from +22% to +320% in the maha season. Likewise, they found that the CO2-induced enhancement of the grain yields of the 16 different genotypes ranged from +4% to +175% in the yala season and from -5% to +64% in the maha season.

What it means
The five Sri Lanka researchers say their results "demonstrate the significant genotypic variation that exists within the rice germplasm, in the response to increased atmospheric CO2 of yield and its correlated physiological parameters," and they go on to suggest that "the significant genotypic variation in this response means that genotypes that are highly responsive to elevated CO2 may be selected and incorporated into breeding programs to produce new rice varieties which would be higher yielding in a future high CO2 climate," whereas Idso and Idso (2000) had merely calculated the increase in yield expected to result from projected increases in the air's CO2 content for existing crop varieties. The latter of these critically important benefits will occur automatically; but to achieve the benefits envisioned by De Costa et al. - and to avert the biological catastrophe foreseen by the scientists cited in the background section of this review - will require that the breeding programs De Costa et al. propose be initiated as soon as possible.

References
Huang, J., Pray, C. and Rozelle, S. 2002. Enhancing the crops to feed the poor. Nature 418: 678-684.

Idso, C.D. and Idso, K.E. 2000. Forecasting world food supplies: The impact of the rising atmospheric CO2 concentration. Technology 7S: 33-55.

Raven, P.H. 2002. Science, sustainability, and the human prospect. Science 297: 954-959.

Tilman, D., Cassman, K.G., Matson, P.A., Naylor, R. and Polasky, S. 2002. Agricultural sustainability and intensive production practices. Nature 418: 671-677.

Tilman, D., Fargione, J., Wolff, B., D'Antonio, C., Dobson, A., Howarth, R., Schindler, D., Schlesinger, W.H., Simberloff, D. and Swackhamer, D. 2001. Forecasting agriculturally driven global environmental change. Science 292: 281-284.

Waggoner, P.E. 1995. How much land can ten billion people spare for nature? Does technology make a difference? Technology in Society 17: 17-34.

Wallace, J.S. 2000. Increasing agricultural water use efficiency to meet future food production. Agriculture, Ecosystems & Environment 82: 105-119.