1270 LIFE : OUTLINES OF GENERAL BIOLOGY 



the different nations. The birth rate has declined most in New 

 South Wales, next in Victoria, next in Belgium, next in Saxony, 

 next in New Zealand, then Germany, then England, and France 

 last of all. To the question, then, is the birth rate increasing or 

 decreasing ? the answer is : decreasing in all civilised countries except 

 Russia and the Balkans, but decreasing at different rates in the 

 various countries. 



How can the population he increasing if the birth rate is decreasing ? 

 Obviously, because the birth rate is at present far in excess of what 

 is needed to compensate for the death rate. The white race has 

 probably an excess of births over deaths of from 12 to 13 '5 per 

 thousand annually. And not only is the birth rate in excess of the 

 death rate; one must take account of preventive medicine and 

 hygiene, agencies securing infant welfare, and so on. For these are 

 gradually lowering the death rate, especially in very early years. 



How many acres would each of us need to keep going ? That is the 

 vital question. No doubt in an island country like Great Britain 

 the supply of fish food is enormously important, but it is not impor- 

 tant in relation to the world as a whole; and, as far as we can judge, 

 the exploitation of the sea, even with a very optimistic outlook on 

 fishery problems, has to-day somewhat narrow limits. The exploita- 

 tion of the sea will not suffice to keep the wolf from the world's 

 door, and we need not refer in detail to mutton and beef, eggs and 

 poultry, since these are all just reincarnated grass. Sixty per cent, 

 of the world's population are living on "grass", or on cereals which 

 are grass, and the question is how much "grass" the world will 

 yield us. The answer involves a very interesting calculation which 

 has been made by various experts, such as Profs. East and Pearl, 

 with great care. In the world at present, if we exclude the Arctic 

 and Antarctic regions, there are 33,000,000,000 acres of surface, but 

 of these only 40 per cent, are arable. So we must reduce our available 

 area at once to 13,000,000,000 acres. What we have to divide up 

 among ourselves is 13,000,000,000 acres of arable ground. Now it 

 seems fairly certain that every man and woman of us requires as 

 a minimum 2*5 acres to live on, 2 J acres to live on without a cow! 

 If 2*5 acres are needed for each individual, we have to divide the 

 total number of available acres by 2-5, and that gives the maximum 

 population which the world will comfortably hold, and the answer is 

 5,200,000,000 individuals as the probable total. It is a curious thing 

 that several of those who have worked at this problem from a differ- 

 ent point of view have estimated the total number at not less than 

 2,000,000,000. The maximum estimate was made by Penck, who 

 suggested a possible total of 8,000,000,000. If we add these two 

 estimates and divide by two, we get 5,000,000,000 people as the 

 world's maximum comfortable population. No doubt there is a good 

 deal of uncertaint^^ Thus some much more effective methods of 



