420 THE FUTURE OF ARID LANDS 
Wild Plants and Animals 
In the above-mentioned setting, the flora and fauna which 
naturally live there have become adjusted to the hostile environ- 
ment and get along reasonably well. The variety of species and 
the number of individuals which can exist in arid zones is remark- 
able. 
Human Population 
In a strictly biological sense, the human race is only one more 
animal species and, to a certain extent, it thrives in arid zones. 
But, given man’s capacity to act upon his environment, it is 
necessary to reserve a separate place for him and to consider him 
as a new element which will fundamentally modify the ones al- 
ready mentioned. 
Domestic Plants and Animals 
Man partly maintains himself from the wild plants and animals 
which exist in arid zones. However, as soon as he establishes 
himself, he introduces domestic types which constitute a new 
element, altering the zone’s natural dynamic equilibrium, that is, 
the equilibrium existing when the impact of human action is not 
felt. 
Balance of the Four Components 
Undoubtedly, there are many possible ways to improve the 
domestic plants and animals in arid zones by applying scientific 
methods of selection, breeding, and cultivation. Nonetheless, the 
attainment of these possibilities is generally accompanied by an 
increase in the local population, making new demands on a natu- 
rally feeble environment and further altering the native flora and 
fauna. 
It must be considered that the prevailing conditions in arid 
zones are really borderline for organic life, and even though it is 
possible to improve them somewhat by human action, it is still 
easier, by the same token, to increase its unfavorable conditions 
until they are not adequate for human existence. 
Therefore, in the question “‘What are the possibilities of main- 
