270 CLOUD 



the earth. They do, however, become dispersed, some of them irretrievably so 

 through oxidation and friction, whereas others require energy and effort to 

 recycle. In addition, exponentially increasing rates of consumption require the 

 placing of ever-larger quantities of metals and other mineral resources into 

 circulation. Human populations must eventually be limited in number, other 

 limits not intervening, by the total sustainable annual crop of food and other 

 renewable resources and by the total quantities of nonrenewable resources that 

 can be put into circulation and kept there. 



It would take too long to develop the arguments here, but they accompany 

 estimates made by the National Academy of Sciences Committee on Resources 

 and Man (1969) which I shall summarize. The estimates say, in effect, that, if 

 all the inventiveness of man could be put to completely efficient use, if luck 

 were with us, and if we did not worry too much about ecological trade-offs, the 

 world might feed eventually, at bare subsistence level, as many as 30 billion 

 people. Now 30 billion people sounds like an awful lot, especially since there are 

 only 3.8 billion of us on Earth now, but it is the number of people that present 

 rates of population growth would put on the earth about 100 years from now. It 

 is doubtful that a nutrient increase of the needed dimensions can be attained 

 within 100 years, if ever. 



The nonrenewable resources are much harder to quantify. Except for a very 

 few of them, we do not know absolute quantities available even within broad 

 limits, and all sorts of variables affect our estimates. It is easier to look at this in 

 terms of what quantities of nonrenewable resources would have to be put into 

 circulation and kept in circulation to sustain the world population expected at 

 the end of the century at a level of living comparable with that of western 

 Europe. Again, without going into detail, but looking at different resources 

 individually, we see that this turns out to be somewhere between 140 and 540 

 times the present annual rates of production for various critical commodities to 

 be put into circulation in the next 30 years. It is very doubtful that this can 

 happen, and the prospective environmental trade-offs are staggering! Thus the 

 aspirations of the developing nations to achieve levels of living comparable to 

 those of the now affluent have little hope of fulfillment in the near future, or 

 ever, without sharp limitation of population and rates of consumption. 



Consider now the cycle of materials in industrial society as shown in Fig. 3. 

 Ultimately most of our industrial materials come out of the earth through 

 mining, metallurgy, and mineral processing. Excluding energy raw materials, we 

 start out with basic raw materials representing only about 1% of the GNP. By 

 means of purification, fabrication, and recombination, with large inputs of 

 energy, these basic raw materials are converted into refined raw materials. 

 Through further processing, they are eventually brought up to final materials for 

 various kinds of goods and services and the fabrication of products. At that 

 point the materials, including the energy that has gone into upgrading them, 

 represent about 40% of the GNP. So you see that even though the start is with a 

 very small quantity — the vitamins or mineral raw materials of industrial 



