Can we raise grain yields fast enough?

Author:Brown, Lester R.
Position:Supply of food against population growth

Many countries have tripled or even quadrupled the amount of grain they produce per hectare of land. But now these gains are slowing, while global demand continues to soar. We need a new strategy for food security.

After a half-century of global surpluses of wheat, rice, corn, and other grains, it is easy to be complacent about the food prospect for the twenty-first century. We have come to take for granted the supply of grain that provides half of humanity's food energy when consumed directly and a good portion of the remainder when consumed indirectly in the form of livestock products.

But this complacency can be dangerous. Each year, as population continues to expand, the world's farmers must stretch their production capacity to feed an additional 80 million people. Beyond that, they must now satisfy the needs generated by record rises in affluence. As people make more money, they consume more beef, pork, poultry, milk, eggs, beer, and other grain-intensive products. A kilogram of pork, for example, may require four kilograms of grain to produce, so as people are able to afford more pork their demand for grain increases. And Third World incomes are now rising at record rates. In Asia, where more than half the world's people live, incomes are rising faster than they have on any continent at any time in history. This combination of more people and more consumption per person is putting heavy pressure on the land.

The world's farmers responded heroically to past increases in demand, nearly tripling the grain harvest from 630 million tons in 1950 to 1.8 billion tons in 1990. Most of this expansion came not from plowing a lot more land, but from more than doubling the amount of grain produced on existing farmland. Between 1950 and 1990, the yield per hectare grew at 2.1 percent per year. Augmented by whatever new land could be added to grain production, including that from expanded irrigation in arid regions, this boosted total grain production by an average of nearly 3 percent a year throughout that four-decade run - well ahead of population growth.

Although there were disastrous shortages from time to time during this period - in China, Ethiopia, and Somalia, for example - and although some 800 million people are still hungry and malnourished, overall supply has not been a major issue. In the United States, the government paid farmers not to plant part of their land. The steady growth in the harvest, and resultant decline in grain prices, created a psychology of surpluses - a psychology that has made it easy for policymakers both to put off the difficult task of stabilizing human population and to take their farmers' capacities to meet future challenges for granted.

The world's total demand for food is likely to nearly double its present level by 2030, and there is little new land available to plow. The key to food security in the years ahead, then, is whether farmers can continue to rapidly raise the productivity of their land, as they have done in the past. However, assessments of the potential for raising land productivity vary widely. In a recent World Bank report, researchers indicated that they expect grain yields to increase at 1.5 to 1.7 percent per year, or "at rates comparable to those in recent years. ..." With this rosy outlook, the Bank projects a surplus capacity in world agriculture as a whole, accompanied by declining food prices. This Worldwatch Institute analysis comes to a very different conclusion.

The World Bank economists base their projections on simple extrapolation, arguing that "historically, yields have grown along a linear path from 1960 to 1990, and they are projected to continue along the path of past growth." Although extrapolating past yield trends worked well enough in previous decades, it won't work in a world where the yields simply are not continuing to climb rapidly. In contrast to the robust increases of 2.1 percent per year between 1950 and 1990, the rise between 1990 and 1995 averaged only 1 percent a year. Although this period is too short to establish a clear trend, it may offer a strong indication of what the future holds.

Reliance on the World Bank projections by governments is leading to underinvestment in both agriculture and family planning. Funding for agricultural research is being cut by many governments, including that of the United States. At the international level, a striking example is the fate of the Philippines-based International Rice Research Institute (IRRI), which gave Asia the high-yielding rices. In 1996, several donor governments, facing cutbacks in their aid budgets, cut their general support funding of IRRI, the world's premier rice research institute, forcing a heavy, cutback in core staff. Similarly, in 1996 the U.S. Congress voted to cut fiscal year 1997 funding of international family planning assistance by 60 percent from 1995 levels, with little consideration of how this would affect the increasingly precarious balance between population and food supply. Fortunately, the new congress voted in early 1997 to restore part of the funding.

The Bank projections breed complacency, not urgency. They permit governments to treat prime cropland like a surplus commodity - one that can be paved over, built on, or otherwise frittered away with impunity. One result can be seen in California's Central Valley, where housing projects are marching up the valley unimpeded, consuming some of the world's finest farmland. In China, this process is taking place on an even larger scale, as the government paves over millions of hectares of cropland so the bicycle can be replaced with the automobile. And in Indonesia, fertile riceland is being converted to golf courses.

The central question now is whether farmers can restore the rapid rise in land productivity. Moreover, that question needs to be addressed in terms that point to realistic possibilities for farmers working under the natural constraints of their own environments - the availability of sunlight, water, and good soil. Rather than analyzing yields on experimental plots or those achieved by the best farmers, this analysis will assess the long-term yield potential under field conditions by individual countries.

The Century of Soaring Productivity

The first recorded case in which a country's farmers achieved a sharp increase in output per unit of land - a "yield takeoff" - began more than a century ago in Japan. In 1878, Japanese rice farmers got an average of 1.4 tons of grain per hectare. By 1984, the average yield had more than tripled, to 4.7 tons. Since then, it has plateaued - fluctuating between 4.3 and 4.6 tons in all but three years. [ILLUSTRATION FOR FIGURE 1 OMITTED] Despite the fact that Japan supports the price paid to its farmers for rice at four times the world level, thereby offering a powerful financial incentive to raise yields higher - and despite its ability to provide the best technology available - it has been unable to improve average yields for more than a decade.

In the United States, the first yield takeoff came more than a half century later, with wheat. During the nearly 80 years between the Civil War and World War II, U.S. wheat yields had fluctuated around 0.9 tons per hectare. As World War II got underway, and demand for U.S. grain rose as production was disrupted abroad, farmers began investing in higher-yielding seeds and in fertilizer. By 1983, yields had climbed to 2.65 tons per hectare, nearly tripling the traditional level. Since then, however, there has been no further rise. Although the wheat yield takeoff in the United States began decades after that of rice in Japan, farmers in the two countries appear to have "hit the wall" at about the same time. Two questions arise: Can scientists restore the historical growth in yields, or does this plateauing in two of the most agriculturally advanced countries signal a future leveling off in other countries, as farmers exhaust the principal means of increasing yields.

The Factors That Increase Yields

The 2.5-fold increase in world grain land productivity since 1950 has come from three sources: genetic advances, agronomic improvements, and some synergies between the two.

On the genetic front, most growth has come from redistributing the share of the plant's photosynthetic product (photosynthate) going to the various plant parts (leaves, stems, roots, and seeds) so that a much larger share goes to the seed - the part we use for food. On the agronomic front (where...

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