44 THE FUTURE OF ARID LANDS 
Combined Resource Use 
We know that the use of rural land depends also upon the use 
of other resources. The more modern science and technology are 
used, the more delicate becomes the balance among separate 
lines of production and among individual resources (2). Even 
similar kinds of land produce very differently in unlike economic 
environments. An efficient agriculture at high levels of labor 
income requires industry, transport, education, and medical 
facilities in the same region. 
Perhaps no example of the principle of combined use is more 
striking than the growing competition for water in arid lands. 
We must think not only of the competition within agriculture, 
which I have already mentioned, but also the competition be- 
tween agriculture, industry, and urban use. Where highly valuable 
mineral deposits can be exploited only with methods requiring 
large amounts of water, this use competes directly with irriga- 
tion. We cannot assume offhand that it is wrong to use water for 
industry and thus deny it to agriculture. Rather, we need to 
develop through research, applicable criteria for appraising the 
long-run benefits to society of alternative combinations of uses. 
Only rarely can any single segment of modern economy succeed 
by itself in any community or region. To do so requires that it 
have an enormous relative advantage. For example, where an 
area 1s so wholly agricultural that all public services must come 
out of agricultural income alone, the soil must be excellent indeed. 
Actually, some of the best agricultural areas of the world are 
located on soils that were of only mediocre quality to begin with. 
This is because agriculture generally thrives best where industry 
and other resource uses contribute to the general economy and 
share in the cost and benefits of the social services. 
Thus there is more to the appraisal of arid lands than examina- 
tions of the soils, vegetation, and water. We must look at the 
other resources and the relation of their use to agriculture and 
to social services. Obviously, we must include fuel and power for 
industry and mineral resources tor mines and factories. Where 
roads and social facilities serve two or more enterprises, eficiency 
is far greater than where they serve a single one. And perhaps 
