48 THE FUTURE OF ARID LANDS 
How big is the challenge so far as area goes? It is difficult to 
get precise figures, but it is generally believed that the total 
land surface of the earth is of the order of twenty-five thousand 
million acres and of this, at present, about two thousand five 
hundred million, or 10%, are under some form of cultivation. 
But it is also estimated that about six thousand four hundred 
million acres are arid, in other words, about one-quarter of the 
total land surface of the earth. That is to say the arid area is Just 
over two and a half times as large as the presently cultivated area. 
Potentialities of Arid Lands 
The end of World War I saw the end of large scale settlement 
in, and development of, new lands by pioneering individuals in 
whom the spirit of adventure or the desire for a freer life was 
strong. Came World War II with a startling realization of the 
precarious way in which most nations lived, a way fraught with 
all the explosive possibilities of further bitter struggles between 
peoples. 
Today we know that Malthus was just ahead of his time and 
we have to ask ourselves whether adequate food requirements of 
the people can be provided from present sources with all the 
technological experience available to us. We suggest that two 
possibilities arise, one a reduction in the rate of growth of the 
population of the world and the other an increase in production 
of foodstuffs not only just to feed people on a minimal diet but 
on a diet nearer to the optimal. With the control of the rate of 
population growth we arid zone people have little or nothing to 
do. We do say, however, with regard to the second, that it is 
possible to increase world food supplies by increasing production 
from present areas and by bringing into production additional 
land at present uneconomically used. 
By applying technological knowledge to the fullest extent in 
what are at present underproducing areas, a great increase in 
food production by individual growers is possible. India, for 
example, possesses irrigation works on a great scale,.and nowhere 
else in the world is so large a population dependent on irrigation 
for food supplies. Nevertheless it is estimated that less than 10%, 
of the runoff of her rivers is utilized. 
