© 1999 Macmillan Magazines Ltd T he Green Revolution was one of the great technological success stories of the second half of the twentieth centu- ry. Because of the introduction of scientifi- cally bred, higher-yielding varieties of rice, wheat and maize beginning in the 1960s, overall food production in the developing countries kept pace with population growth, with both more than doubling. The benefits of the Green Revolution reached many of the world’s poorest people. Forty years ago there were a billion people in developing countries who did not get enough to eat, equivalent to 50 per cent of the population of these coun- tries. If this proportion had remained unchanged, the hungry would now number over two billion — more than double the current estimate of around 800 million, or around 20 per cent of the present population of the developing world. Since the 1970s, world food prices have declined in real terms by over 70 per cent. Those who benefit most are the poor, who spend the highest propor- tion of their family income on food. The Green Revolution brought benefits too for the industrialized world. The high- yielding varieties of staple crop plants bred by the international agricultural research cen- tres of the CGIAR (the Consultative Group on International Agricultural Research) have been incorporated into the modern varieties grown in the United States and Europe. The additional wheat and rice produced in the United States alone from these improved varieties is estimated to have been worth over $3.4 billion from 1970 to 1993 (ref. 1). Yet today, despite these demonstrable achievements, over 800 million people con- sume less than 2,000 calories a day, live a life of permanent or intermittent hunger and are chronically undernourished 2 . Most of the hungry are the women and young children of extremely poor families in developing coun- tries. More than 180 million children under five years of age are severely underweight: that is, they are more than two standard devi- ations below the standard weight for their age. Seventeen million children under five die each year and malnourishment con- tributes to at least a third of these deaths. As well as gross undernourishment, lack of protein, vitamins, minerals and other micronutrients in the diet is also wide- spread 3 . About 100 million children under five suffer from vitamin A deficiency, which can lead to eye damage. Half a million chil- dren become partly or totally blind each year, and many subsequently die. Recent research has shown that lack of vitamin A has an even more pervasive effect, weakening the protec- tive barriers to infection put up by the skin, the mucous membranes and the immune system 4 . Iron deficiency is also common, leading to about 400 million women of childbearing age (15–49 years) being afflict- ed by anaemia. As a result they tend to pro- duce stillborn or underweight children and are more likely to die in childbirth. Anaemia has been identified as a contributing factor in over 20 per cent of all maternal deaths after childbirth in Asia and Africa. If nothing new is done, the number of the poor and hungry will grow. The populations of most developing countries are increasing rapidly and by the year 2020 there will be an additional 1.5 billion mouths to feed, mostly in the developing world. What is the likelihood that they will be fed? The end of the Green Revolution The prognosis is not good. As indicated in Fig. 1, there is widespread evidence of decline in the rate of increase of crop yields 5–7 . This slowdown is due to a combination of causes. On the best lands many farmers are now obtaining yields close to those produced on experimental stations, and there has been little or no increase in the maximum possible yields of rice and maize in recent years. A second factor is the cumulative effect of environmental degradation, partly caused by agriculture itself. Simply exporting more food from the industrialized countries is not a solution. The world already produces more than enough food to feed everyone if the food were equally distributed, but it is not. Market economies are notoriously ineffective in achieving equitable distribution of benefits. There is no reason to believe that the poor who lack access to adequate food today will be any better served by future world markets. Food aid programmes are also no solution, except in cases of specific short-term emer- gency. They reach only a small portion of those suffering chronic hunger and, if prolonged, create dependency and have a negative impact on local food production. About 130 million of the poorest 20 per cent of people in developing countries live in cities. For them, access to food means cheap food from any source. But 650 million of the poorest live in rural areas where agriculture is the primary economic activity, and as is the case in much of Africa, many live in regions where agricultural potential is low and nat- ural resources are poor 8 . They are distant from markets and have limited purchasing power. For them, access means local produc- tion of food that generates employment and income, and is sufficient and dependable enough to meet local needs throughout the year, including years that are unfavourable for agriculture. All these arguments point to the need for a second Green Revolution, yet one that does not simply reflect the successes, and mistakes, of the first. In effect, we require a ‘Doubly Green Revolution’, an agricultural revolution that is both more productive and more ‘green’ in terms of conserving natural resources and the environment than the first. We believe that this can be achieved by a combination of: ecological approaches to sustainable agri- culture; greater participation by farmers in impacts NATURE | VOL 402 | SUPP | 2 DECEMBER 1999 | www.nature.com C55 Feeding the world in the twenty-first century Gordon Conway and Gary Toenniessen The gains in food production provided by the Green Revolution have reached their ceiling while world population continues to rise. To ensure that the world’s poorest people do not still go hungry in the twenty-first century, advances in plant biotechnology must be deployed for their benefit by a strong public-sector agricultural research effort. Average increase in yield (kg Ha –1 ) 90 80 70 60 50 40 30 20 10 0 Maize Wheat Rice 1965–74 1975–84 1985–94 Figure 1 Average annual increase in yields of rice, wheat and maize in developing countries by periods.