Criteria for assessing the adequacy of a national average diet are proposed, and the global average cereal production per capita needed to provide an adequate average diet is calculated. The technical feasibility of maintaining global food production per capita up to the year 2050 is assessed. The required input of nitrogen fertilizer is estimated and the water supply in relation to crop evapotranspiration is discussed. It is shown that maintenance of the present global cereal production per capita would be accompanied by a moderate increase in grain consumption per capita in the less-developed countries. but that this will involve a major increase in the net import of grain from the more-developed countries. Achievement of a satisfactory average diet in the less-developed countries as a whole cannot be achieved until the population of this group of countries has declined to a level substantially below its future peak. (C) 2002 Published by Elsevier Science Ltd.
