An American farmer in 1900 fed seven people; today his great grandson feeds 96 people. World grain output rose from 400 million tons in 1900 to 1.9 billion tons in 1998. The spectre of soil exhaustion has been threatened over and over again since Malthus' day, but in fact yields per hectare have contined to rise ever since (from 1.1 tons to 2.7 tons between 1981 and 2000).
The threat to food has not come from soil exhaustion, but from policies of land retirement adopted by the big producers like the European Union which has retired 3.8 million hectares under the set aside scheme. World wide land area re-designated as national park - where farming is not forbidden, but discouraged - has grown from 2.4 million sq KM to 18.8 million sq KM between 1962 and 2003. In 2005 those managed land retirement schemes began to force food prices upwards.