INFLUENCE OF MAN ON SOIL FERTILITY — JACKS 337 



the existing balance of Nature either by adopting shifting cultivation 

 in forest lands or by nomadism in grasslands; then, with increasing 

 population, upsetting the balance of Nature by the practice of settled, 

 subsistence agriculture with social checks on the unavoidable exhaus- 

 tion of the soil; then the concentration of the growing population 

 into towns, the creation of new wealth in manufacturing, commerce, 

 and the arts, a rise in the urban standard of living, a demand for more 

 of the necessities of life, an overflow of wealth into the soil, and the 

 creation of new fertility to satisfy the towns' demands; finally, the 

 reestablishment of a biotic balance when the inflow of soil fertility is 

 balanced by the outflow. As long as most of the population is urban 

 there is no apparent upper limit to the number of people who can live 

 in a region or country without exhausting its soil ; but the present-day 

 condition of southeast Asia suggests that a relatively low total popu- 

 lation density can be a heavy burden on the soil when most of the 

 people live on the land. By contrast, the countries showing the highest 

 average soil fertility are the most densely populated and highly in- 

 dustrialized — Britain, Germany, Holland, Belgium, Japan — and agri- 

 cultural Denmark, the exception to prove the rule. 



Today, as a result of the rapid opening-up and development of a 

 large part of the habitable land within the past century, most of the 

 world is in the soil-exhausting phase, a fact which, unless viewed in 

 ecological perspective, may lead to a certain loss of faith in the future 

 of mankind. But it is a passing phase, which seems alarming only 

 because it is happening over such large areas at the same time. Already 

 we can see signs in some rich new countries that the soil-conserving 

 phase is approaching. Will the world of a hundred years hence be 

 able to feed the 6,000 million people who will then be in it? The 

 answer is yes, provided most of them live in towns and produce enough 

 wealth to pay for the food they need. If they offer enough money for 

 their food, the food will be produced. As every farmer knows, it pays 

 to fertilize when the market is good. That may, perhaps, be regarded 

 as an oversimplification of the phenomena of civilization ; nevertheless 

 it explains quite a lot of them. 



