THE ECONOMIC IMPORTANCE OF FORESTS 501 



the stripped timber a total loss and danger in case of fire, is an- 

 other barbarous waste for which man is responsible. . 



Fire is one of the forests' worst foes and except for lightning, 

 man is the author of them all. Sparks from locomotives and camp 

 fires of careless hunters account for some which start accidentally, 

 while grazers and berry pickers start fires on purpose to help their 

 crops, and men, clearing land, often lose control of their fires and 

 cause great destruction. In 1915 there were 40,000 fires, covering 

 6,000,000 acres, or over 1 per cent of all forests in United States, 

 which caused a loss of $7,000,000 and many lives. During the 

 same year 2j million were spent for forest protection or only 

 one-third the year's loss. 



Insect Enemies. In our study of insects, the damage which 

 they do to crops was mentioned, and the forest crops are no ex- 

 ception. The saw fly, bark beetles, gyspy moth, tent caterpillar, 

 and tussock moth are some of the most harmful, and, unlike the 

 orchard pests, the extent of the forests makes spraying impos- 

 sible. The birds are almost our sole protection against these 

 forest enemies, though toads, snakes, and ichneumon flies do 

 their share. 



Fungus Enemies. Whenever we see a shelf fungus on a tree 

 we may be sure that tree is doomed unless help is provided. But 

 the most damage is done by less conspicuous forms, such as the 

 rusts and blights, of which the chestnut blight is a notable ex- 

 ample. (Not only are the trees destroyed but their lumber is 

 ruined by fungi, both in standing timber and often after it is cut 

 and piled.) 



Weather Conditions. Despite their great strength, trees often 

 fall victims to wind and snow, and in many regions great, strips 

 are blown down by tornadoes making the almost impassable 

 " windfalls " which later, when dead and dry, furnish ideal fuel 

 for forest fires. Sleet storms destroy many buds and even large 

 branches, especially if followed by severe winds, and thus damage 

 or kill many valuable forest trees. 



Grazing Animals and Others. Large herds of cattle or sheep 

 often damage forests by trampling on the young trees and by 



