In Beijing, the water table has dropped in 40 years from 15 feet below ground level to more than 150 feet. Increased industrial and residential needs, heightened by the demand for indoor plumbing and flush toilets in developing countries, means less river water available for farming. Brown notes that recently China's great Yellow River completely disappeared some 620 kilometers from its mouth in the Yellow Sea. In concentrating on land-based food production, Brown doesn't ignore the oceans. But he is clear that we have reached the limits of the oceans' fisheries, and that this puts more pressure on land-based food.
Global affluence is another factor.
Along with rising incomes, world meat consumption has gone up from 44 million tons to 134 million tons since 1950. Rising meat consumption in China, Brown says, has changed them in the last two years from a grain exporter of 8 million tons, to a grain importer of 16 million tons, second only to Japan. If the food situation continues to deteriorate, with no prospect of reversal, people in those societies least able to compete for these supplies will begin to lose hope. With the loss of hope comes the risk of social disintegration. Just to feed these extra 90 million people takes 78,000 tons of grain every day - 28 million tons a year.