TENURE AND USE OF ARID GRAZING LANDS, 11 
have been done .which tend to lower the productivity of the area. 
One effect is a reduction in the total amount of water that enters the 
soil, with a lessening of the amount available to the growing plants. 
The amount of feed that plants produce varies almost directly as the 
available water, up to the optimum amount. Therefore loss of the 
water means loss of feed on any arid land, because the water supply 
on such land is always less than might be utilized. 
Another effect of the removal of the grass is an increase in the ero- 
sion produced by the water that runs off [83] 9 . Nothing protects a 
soil from erosion so well as a thick sod of grass. Any practice which 
retards the rate of flow of the water reduces its erosive power many 
fold. All erosion takes away the finer soil and leaves a surface upon 
which the desirable plants will not readily grow. The process is 
cumulative and is often carried so far that nothing but an entirely 
new plant association can occupy the land and the land lies bare and 
unproductive for a longer or shorter period while the new association 
is coming in and getting adjusted. This new association nearly 
always starts as a scattering growth of aggressive and often unpala- 
table weeds. 
It is very hard to maintain a balance between the maximum pro- 
duction of the better forage plants and the maximum number of 
animals that can be fed upon the area [41]; it is practically impossible 
to do so upon an open range, where possession is maintained only by 
having the land overstocked all the time. 
Poisonous plants. — Certain of the plants on the ranges are poison- 
ous to stock. The natural tendency of the animals to leave such 
plants alone because they are usually not palatable tends to favor 
them in their competition with more valuable plants, with the final 
result that the poisonous plants tend to increase in quantity as time 
goes on. Under certain circumstances poisonous plants are eaten 
by the animals (usually for lack of better feed) and serious losses are 
suffered. (See bibliography, section 9). 
Wild animals. — Besides the domestic stock on a range there are 
always wild animals, some of which will attack the domestic stock. 
The extinction of these predatory animals is always an important 
matter in the range stock business, but when accomplished, it has a 
reaction which is not altogether desirable. Other wild animals, like 
prairie dogs and rabbits, that are normally the food of the coyotes, 
wolves, etc., reproduce rapidly whenever their natural enemies are 
removed and then they must themselves be removed or they eat up 
the feed that is needed for the stock. Hence there is a close relation- 
ship between the stockman's business and the work of the U. S. 
9 The transporting power of flowing water varies as the sixth power of its velocity. Le Conte, Elements 
of Geology, 5th ed., p. 20, 1903. 
