Volume 4, Number 43: 24 October 2001
Damage to crops caused by air pollutants is one of the major scourges of present-day agriculture. How great are the production losses caused by these plant-debilitating agents? In a recent study of the effects of ozone pollution in the Punjab region of Pakistan, Wahid et al. (2001) periodically applied a powerful ozone protectant to soybean plants growing in three different locations in the general vicinity of the city of Lahore - a suburban site, a remote rural site, and a rural roadside site - throughout two different growing seasons (one immediately post-monsoon and one the following spring or pre-monsoon). The results were truly astounding. At the suburban site, application of the ozone protectant increased the weight of seeds produced per plant by 47% in the post-monsoon season and by 113% in the pre-monsoon season. At the remote rural site, the corresponding yield increases were 94% and 182%; and at the rural roadside site, they were 170% and 285%. Averaged across all three sites and both seasons of the year, the mean increase in yield caused by countering the deleterious effects of this one major air pollutant was nearly 150%.
Due to their somewhat surprising finding that "the impacts of ozone on the yield of soybean are larger in the rural areas around Lahore than in suburban areas of the city," the authors concluded "there may be substantial impacts of oxidants on crop yield across large areas of the Punjab." In addition, they noted that earlier studies had revealed similar large ozone-induced losses in the productivity of local cultivars of wheat and rice. Hence, it is clear that whatever could be done to reduce these massive crop losses - or, ideally, eliminate them altogether - would be a godsend to the people of Pakistan and the inhabitants of many other areas of the globe.
Fortunately, such a savior is silently working its wonders throughout the entire world. That of which we speak, of course, is the ongoing rise in the air's CO2 content, which counteracts the negative effects of ozone - and those of many other air pollutants (Allen, 1990; Idso and Idso, 1994) - by restricting the noxious molecule's entry into plant leaves via induced reduction of leaf stomatal apertures (Reid and Fiscus, 1998), and by ameliorating its adverse biochemical activities when it does penetrate vegetative tissues (Reid et al., 1998).
In a number of studies of these beneficial consequences of atmospheric CO2 enrichment for the crop studied by Wahid et al., i.e., soybeans, it has been found that a nominal doubling of the air's CO2 concentration is sufficient to greatly reduce - and in some cases completely eliminate - the yield-reducing effects of ozone pollution (Heagle et al., 1998a and 1998b; Miller et al., 1998; Reid and Fiscus, 1998; Reid et al., 1998). The same conclusion follows from the results of several studies that have looked at wheat in this regard (Heagle et al., 2000; McKee et al., 2000; Pleijel et al., 2000; Tiedemann and Firsching, 2000). In fact, the work of Volin et al. (1998) suggests that these CO2-induced benefits will likely be experienced by all plants. As the researchers directly state in the title of their paper: "species respond similarly regardless of photosynthetic pathway or plant functional group."
Think about the implications of these findings. A doubling of the air's CO2 content could well double agricultural production in many areas of the world by merely eliminating the adverse effects of but one air pollutant, i.e., ozone. Then, consider the fact that by the mid-point of the current century, we will likely face a food production crisis of unimaginable proportions (see our Editorials of 21 February 2001 and 13 June 2001). Finally, ask yourself what the Precautionary Principle has to say about this state of affairs (see our Editorial of 4 July 2001). We conducted such an exercise in our review of the paper of Hudak et al. (1999), concluding that perhaps our new mantra should be: Free the Biosphere! Let the air's CO2 content rise.
And we still feel that way. CO2 is the elixir of life. It is one of the primary raw materials - the other being water - out of which plants construct their tissues; and it is essential to their existence and our existence. Without more of it in the air, our species - as well as most of the rest of the planet's animal life - will not survive the 21st century intact. The biosphere will continue to exist, but not as we know it; for most of its wild diversity of life will have been extinguished by mankind's mad rush to appropriate ever more land and water to grow the food required to feed itself (Tilman et al., 2001).
So we say again, let the air's CO2 content rise. It's the right thing to do, both scientifically and morally.
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Dr. Sherwood B. Idso President |
Dr. Keith E. Idso Vice President |
References
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Heagle, A.S., Miller, J.E. and Pursley, W.A. 1998b. Influence of ozone stress on soybean response to carbon dioxide enrichment: III. Yield and seed quality. Crop Science 38: 128-134.
Heagle, A.S., Miller, J.E. and Pursley, W.A. 2000. Growth and yield responses of winter wheat to mixtures of ozone and carbon dioxide. Crop Science 40: 1656-1664.
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