SHADE TREES AND FORESTS 499 



no plans for future returns. Usually the piles of brush left 

 have been a prolific means for the spread of forest fires. 

 Sometimes this short-sighted policy has been hastened by 

 the fear of possible loss through fires and by high taxes which 

 rendered it unprofitable to hold the land for more than one 

 crop. 



Grazing. Grazing may do injury to the forests if not 

 properly regulated. The sheep trample the young growth 



FIG. ig6. Destructive lumbering. The slash enabled fire to complete the ruin. 



under foot and destroy small trees by browsing on the young 

 shoots. Sheep may also pulverize the forest floor, allowing 

 it to be washed away by storms. This matter is being 

 carefully regulated in the national forests, and less harm is 

 done than formerly. 



Insects. It has been estimated that insects cause an 

 annual loss to trees in this country of one hundred million 

 dollars. There are hundreds of species of insects found 

 attacking the forest trees, but the greater amount of the 

 damage is done by a comparatively small number of species. 



