HISTORY AND PROBLEMS 23 
With the exception of squirrels and rabbits, modern man has 
almost neglected this group as a food source. Rodents probably 
are the greatest consumers of plant material and on these 20,000 
species man and other carnivores could largely depend for food. 
They among mammals seem to have made the greatest adjust- 
ments to life in an arid environment. Yet modern man has re- 
garded them largely as pests and competitors of his larger domesti- 
cated mammals. It would seem possible to explore this resource 
as a food source for man, as have the more primitive peoples of 
the earth. 
Nature set almost impossible tasks for the plant and the animal 
world. Water, the substance about which all life was developed, 
would seem to be all essential. Here in the drought deserts nature 
has provided a minimum of supply. At the same time the tem- 
perature and other atmospheric conditions demand the greatest 
amount of water. In the plant world the challenge has been met 
wonderfully and almost all of the earth surface has been occupied. 
The same is true of the animal world. 
Modern man has been given mighty instruments to extend this 
use. So far he has relied largely on engineering skill to lead waters 
into this desert region from regions of ample supply. He has not 
accomplished much in economical use for he still grows crops 
during the hot dry part of the year at a very high rate of water 
consumption. Neither has he attempted under irrigation to im- 
prove the efficiency of these irrigated crops in the use of water. 
Ground water has been too generally regarded as a renewable 
resource but experience has often proved it to be largely non- 
renewable. 
He hopes to demineralize sea and alkali waters when the demand 
justifies the expense, thus to aid in a small degree nature’s great 
distillery which pours over the land an average of about 30 inches 
of water of the highest quality each year. He likewise hopes to 
control to a degree the distribution of this rainfall and to direct 
it to more arid areas. 
One thing he can hope to accomplish and that is to stop the 
enormous loss of water to the ocean, when it is so badly needed on 
land adjacent to the streams that carry it away. 
Nature has produced a magnificent controlled area occupying 
