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African Food Security:
The Need for a "Doubly Green Revolution"

Volume 6, Number 12: 19 March 2003

Some two-tenths of a billion Africans, give or take a few million, are undernourished (FAO, 2001).  Most of them are children, who according to the Rockefeller Foundation's Gordon Conway and Gary Toenniessen, "do not have access at all times to enough food to lead active, healthy lives."  What is more, the situation is deteriorating.

Writing in the 21 February 2003 issue of Science, the Rockefeller Foundation duo says the downward trend in food production per capita is the result of rapid population growth and poor crop production, the latter of which problems they attribute to low soil fertility and the negative effects of crop pests, diseases and abiotic environmental stresses.

What can be done to remedy this unfortunate situation?  Building on their earlier call for a second Green Revolution (Conway and Toenniessen, 1999), the two food specialists describe a program that appears to have great potential to reduce the severity of Africa's food shortfall.  In a nutshell, they say it is based on intensifying agricultural production "with genetic and agro-ecological technologies that require only small amounts of additional labor and capital," describing the development and application of these technologies as comprising a "Doubly Green Revolution."

Although we admire the zeal with which Conway and Toenniessen approach this worthy cause and acknowledge its tremendous importance and the efficacy of the techniques they champion for accomplishing its goals, we feel the appellation they attach to it is a major misnomer.  Much good can indeed come from applying human ingenuity to the problem of food insecurity; yet the result is but a single integrated approach.  In addition, this approach has been demonstrated by Tilman et al. (2001) to be insufficient to meet future food needs.  As the latter group of thoughtful scientists has rightly concluded after careful study of the issue, "even the best available technologies, fully deployed, cannot prevent many of the forecasted problems."

So what is the other half of the required and truly "Doubly" Green Revolution?  It is, as we have long advocated (Idso and Idso, 2000), allowing the air's CO2 concentration to rise unimpeded so that the many proven benefits of atmospheric CO2 enrichment may be bestowed upon the planet's natural vegetation and mankind's crops, all without the need for any "additional labor and capital."

But can we really get something for nothing?  Yes we can.  Conway and Toenniessen (2003) describe how ameliorating four major impediments to plant growth significantly boosts crop yields.  These impediments are (1) soil infertility, (2) weeds, (3) insects and diseases, and (4) drought.  Reducing the negative consequences of each of these yield-reducing factors, as the Rockefeller scientists demonstrate, boosts crop productivity in an additive manner.  In what follows, we describe how merely not interfering with the ongoing rise in the air's CO2 content accomplishes the very same things, and that it does so on top of what human ingenuity is able to accomplish, resulting in yet additional benefits.

In the case of soil infertility, many experiments have demonstrated that even when important nutrients are present in the soil in less than optimal amounts, enriching the air with CO2 still boosts crop yields.  With respect to the soil of an African farm where their "genetic and agro-ecological technologies" have been applied, for example, Conway and Toenniessen speak of "a severe lack of phosphorus and shortages of nitrogen."  Even in such situations, materials archived in our Subject Index provide several examples of how atmospheric CO2 enrichment enhances plant growth under these adverse conditions [see Growth Response to CO2 With Other Variables (Nitrogen -- Agricultural Crops) and Growth Response to CO2 With Other Variables (Phosphorus)].  Furthermore, if supplemental fertilization is provided as described by Conway and Toenniessen, these same Subject Index sections provide examples of even larger CO2-induced benefits above and beyond those provided by the extra nitrogen and phosphorus applied to the soil.

In the case of weeds, Conway and Toenniessen speak of one of Africa's staple crops, maize, being "attacked by the parasitic weed Striga (Striga hermonthica), which sucks nutrients from roots."  This weed also infects many other C4 crops of the semi-arid tropics, such as sorghum, sugar cane and millet, as well as the C3 crop rice, particularly throughout much of Africa, where it is currently one of the region's most economically important parasitic weeds.  Here, too, materials archived on our website describe how atmospheric CO2 enrichment greatly reduces the damage done by this devastating weed [see our Journal Reviews of Watling and Press (1997) and Watling and Press (2000)].

In the case of insects and plant diseases, atmospheric CO2 enrichment also helps prevent crop losses.  In a study of diseased tomato plants infected with the fungal pathogen Phytophthora parasitica, which attacks plant roots inducing water stress that decreases yields, for example, the growth-promoting effect of a doubling of the air's CO2 content completely counterbalanced the yield-reducing effect of the pathogen (Jwa and Walling, 2001).  Likewise, in a review of impacts and responses of herbivorous insects maintained for relatively long periods of time in CO2-enriched environments as described in some 30-plus different studies, Whittaker (1999) noted that insect populations, on average, have been unaffected by the extra CO2.  Since plant growth is nearly universally stimulated in air of elevated CO2 concentration, however, a smaller proportion of it would thus be likely to be consumed by herbivorous insects in a high-CO2 world.

Lastly, in the case of drought, we again have the nearly universal bettering of plant water use efficiency that is induced by atmospheric CO2 enrichment [see Water Use Efficiency (Agricultural Species) in our Subject Index, as well as the Grassland Species and Woody Species subheadings].

In conclusion, in essentially every major way in which human ingenuity can increase crop productivity to help feed the poor of Africa -- or anywhere else, for that matter -- the ongoing rise in the air's CO2 content can greatly add to whatever man can do, thereby producing a truly "Doubly" Green Revolution that is absolutely essential to preventing future food shortages.  Will we be intelligent enough and caring enough to channel our efforts in the directions needed to rise to this challenge?  Or will we do all in our power to fight against the very phenomenon that can prove our salvation?  These are questions that are too important to be left to others to decide.  Each of us has a responsibility to act in accordance with what he or she knows to be scientifically factual.  To acquiesce to what is merely politically fashionable is to abdicate that which sets us apart from all creation and makes us moral.

Sherwood, Keith and Craig Idso

Conway, G. and Toenniessen, G.  1999.  Feeding the world in the twenty-first century.  Nature 402 Supp: C55-C58.

Conway, G. and Toenniessen, G.  2003.  Science for African food security.  Science 299: 1187-1188.

FAO.  2001.  The State of Food Insecurity in the World 2001.  Food and Agriculture Organization, United Nations, Rome, Italy.

Idso, C.D. and Idso, K.E.  2000.  Forecasting world food supplies: The impact of the rising atmospheric CO2 concentration.  Technology 7S: 33-56.

Jwa, N.-S. and Walling, L.L.  2001.  Influence of elevated CO2 concentration on disease development in tomato.  New Phytologist 149: 509-518.

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.

Watling, J.R. and Press, M.C.  1997.  How is the relationship between the C4 cereal Sorghum bicolor and the C3 root hemi-parasites Striga hermonthica and Striga asiatica affected by elevated CO2Plant, Cell and Environment 20: 1292-1300.

Watling, J.R. and Press, M.C.  2000.  Infection with the parasitic angiosperm Striga hermonthica influences the response of the C3 cereal Oryza sativa to elevated CO2Global Change Biology 6: 919-930.

Whittaker, J.B.  1999.  Impacts and responses at population level of herbivorous insects to elevated CO2European Journal of Entomology 96: 149-156.