A few generations ago thoughtful people looked forward to over- 

 crowding in the fear that it would lead to great destruction of human 

 life, or at least to great suffering. Indeed, the poverty and hunger of 

 past times were largely due to man's inability to obtain from the soil 

 adequate supplies of food. At the present time, however, our special 

 knowledge and processes are so advanced that we are able to produce food 

 and other essentials and many conveniences far in excess of the quantities 

 needed for general comfort. We are, in fact, producing more foods of 

 various kinds than we are able to distribute through existing systems of 

 exchange — that is, through our business and financial machinery. This 

 does not mean that everyone has all the food he needs. Even before the 

 Second World War, not only was a very considerable part of our popula- 

 tion misnourished, but a substantial part was actually undernourished. 



Saving the Soil Increasing agricultural efficiency and activity does 

 not assure abundance for everybody. Over large parts of the country we 

 have made every cultivated acre yield three or four times as much food 

 as had been usual in past generations. At the same time, we have removed 

 from many areas tremendous quantities of minerals, so that the fertility of 

 the soil is gone. And in addition, our ways of working the soil have ruined 

 millions of acres by removing that portion of the earth's crust which is usable 

 for crop production. 



Under natural conditions, where the soil is covered with forest or grass, 

 the topsoil builds up slowly from the weathering of rock material and the 

 accumulation of organic debris (see illustration, p. 153). Even though some 

 erosion takes place, the building-up processes more than make up for the 

 loss. But we have removed the native cover of trees, shrubs, vines and grass. 

 We have pulverized the soil and exposed it to the elements year after year, 

 as in row-crop, or clean-culture, farming. As a result, soil has been removed 

 from the top much faster than it is built up from below. Water and wind 

 have carried the loose topsoil from the exposed hillsides and gullies into 

 valleys and streams. After the topsoil has gone from the hills, the poor 

 subsoil washes away, too, and in many cases covers the rich soil previously 

 deposited in the valleys. 



In Brief 



Carbohydrates originate in green plants through the action of sunlight 

 upon water and carbon dioxide in the presence of chlorophyl; oxygen is a 

 by-product of this photosynthesis. 



All other organic materials are derived from carbohydrates. 



Both plant cells and animal cells synthesize fats from starches and sugars. 



When supplied with carbohydrates and suitable mineral salts, non-green 



156 



