Feeding an ever-larger world population predicted for the future will require an agricultural system that stays apace of population growth. Achieving such a system will not be easy. In fact, although total yields continue to increase on a global basis, there is a disturbing decline in the rate of yield growth . If such a slowdown persists, it could prevent production levels from rising as much as is needed in the next few decades.
What has been termed a “yield plateau” or “yield stagnation” has been detected in many of the globe’s major crops, especially for the cereals from which people get most of their food energy . For wheat, yield growth rates slid from 2.92 percent per year for the period from 1961 to 1979 to 1.78 percent for the period from 1980 to 1997. For maize, the rates slipped from 2.88 percent to 1.29 percent during the same period. For paddy rice, yield growth rates have remained stable at 1.95 percent . (See ” Yields Are Up, But Growth is Slowing: Global Changes in Cereal Yields, 1961-96” and “Yield Growth Rates, 1961-96”.) Yet the demand for all cereals is expected to rise substantially in the next two decades .
|Yields are up, but growth is slowing|
|Source: Food and Agriculture Organization of the United Nations (FAO), FAOSTAT Statistical Database (FAO, Rome, 1997).
Note: Values are un-weighted 5-year moving averages.
Throughout history, whenever more food has been needed, people have simply cleared more land to plant more crops. However, most high-quality agricultural land is already in production, and the environmental costs of converting remaining forest, grassland, and wetland habitats to cropland are well recognized. Even if such lands were converted to agricultural uses, much of the remaining soil is less productive and more fragile; thus, its contribution to future world food production would likely be limited. The marginal benefit of converting new land increases the importance of continuing to improve crop yields so the existing agricultural lands can produce additional food .
Several factors may be contributing to the yield plateau. The most direct ways of increasing yields – planting new varieties, extending irrigation, and using fertilizer – were already exploited in many locations during the Green Revolution of the 1960s and 1970s. In addition, the emphasis of much recent agricultural research has been on achieving goals other than increased yields, such as improving drought tolerance or resistance to insects and disease.
More important, world cereal prices have declined in recent years, and grain farmers who might have justified the expense of additional inputs (e.g., fertilizer and water) to keep yields up have shifted away from cereals to more profitable crops.
References and notes
1. World Resources Institute calculation using data from Food and Agriculture Organization of the United Nations (FAO), FAOSTAT Statistical Database (FAO, Rome, 1997).
2. Mark D. Winslow, special assistant to the associate director general (research), International Crops Research Institute for the Semi-Arid Tropics, July 16, 1997 (personal communication).
3. Op. cit. 1.
4. Nikos Alexandratos, ed., World Agriculture: Towards 2010 (Food and Agriculture Organization of the United Nations and John Wiley and Sons, Chichester, 1995), pp. 168-169.
5. International Rice Research Institute (IRRI), Program Report for 1995 (IRRI, Los Ba<@241>os, Philippines, 1996), p.3.