234 THE FUTURE OF ARID LANDS 
to take advantage of favorable periods and to guard against the 
unfavorable weather events which are bound to happen. Perhaps 
the old frontier rule of preparing for the worst while hoping for 
the best is still a good guide for arid land residents. 
In the southwestern United States there are many examples of 
the improper use of arid lands. Present day problems in the Rio 
Grande Valley are to a large extent the result of poor land use in 
the past. Historical evidence clearly shows that a general decline 
of watershed lands and resources began during the 1880’s. This 
decline was largely brought on by damage to the natural plant 
cover through poor grazing management, promiscuous wagon 
trailing, and injudicious dry Penta hs evidences of decline 
are: the decreased grazing capacity of range lands; deep and con- 
tinuous gullies slashed through alluvial valleys; shifting sand and 
sand dunes; and the silting up of river channels and storage 
reservoirs. Much of the water yield is now from surface runoff and 
is silt laden. Water once held in the soil to support plant growth 
is now drained out by deep gully channels. Irrigation diversions 
on tributaries have been undercut and destroyed. The Rio Puerco 
is a terrifying example of the destruction caused by accelerated 
erosion. The lower valley of the Rio Puerco between San Luis and 
Cabezon and in the vicinity of Salazar once supported a prosper- 
HUMID ARID 
SOIL 
Figure 1. Diagrammatic illustration emphasizing that.a more deli- 
cate adjustment of vegetation, rainfall, and soil exists in arid lands than 
is common in humid lands. This vegetation-environment relationship 
must be recognized in the sustained use of grass and forest lands in arid 
regions. 
