But the Green Revolution represented only a "temporary success," as Norman Borlaug, the Danish-American plant geneticist who was one of its architects, noted upon receiving the 1970 Nobel Peace Prize for his contribution (25). Borlaug pointed out that it is not enough to boost yields on existing cropland; slowing population growth also is crucial.

The first Green Revolution raised the productivity of the three main staple food crops—rice, wheat, and corn (83, 99). Between 1950 and 1990 grain yields increased by nearly two and a half times, from 1.06 metric tons per hectare to 2.52 tons (98). A second revolution also must raise the productivity of other important food crops such as sorghum, millet, and cassava—foods produced and consumed mainly by the world's poor (45, 55, 98, 99).

Workers plant rice cuttings at an experimental rice farm near Bombay, India, in 1962. The Green Revolution that began in the 1960s has helped keep food production ahead of population growth. But it amounts to only a temporary success. Now, a second Green Revolution is needed.

So far, the outlook for a second Green Revolution is uncertain. Because most increases in food supplies must come from currently cultivated land, raising productivity will require new technologies and better farming practices. Poor people, however, cannot afford the large amounts of fertilizers, pesticides, and other agricultural inputs that increased yields in the first Green Revolution (46). Moreover, the population of developing countries is much larger than it was in the 1960s, the amount of arable land per person is less, and natural resources are more degraded. Nevertheless, three recent developments are promising:

• Super rice. The International Rice Research Institute (IRRI) in the Philippines has developed a new strain of super rice capable of boosting yields by 25%, amounting to an extra 100 million metric tons a year—enough to feed an additional 450 million people. This rice does not promise to produce well on marginal land, however, and therefore its use may be limited to well-irrigated bottom land (61, 64, 66).
• Improved corn. The International Center for the Improvement of Maize and Wheat in Mexico has engineered several improved varieties of corn that could increase yields by up to 40%. These varieties could be grown on marginal land under difficult growing conditions and thus could be raised by poor farmers. If widely used, the new varieties could feed an additional 50 million people a year (34).
• A new potato. The International Potato Centre in Peru claims that, for an investment of US$25 million, it could produce a new potato that would be resistant to a virulent form of potato blight that has reached every continent except Australia (64).