HERMAN H. CHAPMAN 73 



must of necessity be local, and will be felt, at most, only 

 a very few miles from the forest borders. 



Influences of Forests on Streams and Soil Erosion. 



But when we consider the influence of forests upon the 

 behavior of the water which falls as rain, and its influence 

 on the soil and on streams, the facts are indisputable. 

 Rain falling on bare soil hardens it by impact and decreases 

 its absorptive power. In heavy downpours, the water, 

 unable to sink into the soil, rushes off in surface streams 

 which soon wash out gullies. The more exaggerated these 

 conditions become, the more rapidly will the rainfall be 

 drained into streams, causing sudden freshets, which de- 

 stroy bridges and wash out or cover bottomlands with sand 

 and boulders. Any influence which retards the flow of 

 rainwater and increases the amount absorbed by the 

 ground, will tend to equalize the flow of streams. This to 

 a marked extent the forest accomplishes. The force of the 

 rain is broken by the branches, while the leaf litter and 

 other rubbish impede the flow of the water. The litter 

 and humus cover, not only take up water in large quantities, 

 but keep the soil porous below. Much of the water so ab- 

 sorbed appears as springs and it is everywhere noted that 

 the destruction of a forest cover causes springs to dry up. 

 In many places, the retarding effects of forests on runoff 

 have been compared by actual measurements and found to 

 be very pronounced. Soil thus protected cannot wash. It 

 is in mountainous regions that these effects are most 

 noticed and here the need of forest protection is greatest. 



Government Regulation versus Government Ownership. 



For these reasons it is not safe to allow owners to re- 

 move timber from steep mountain slopes, and in many 

 countries laws are enforced regulating such cutting. But 

 even in European states whose citizens are used to being 

 interfered with by the government, it has not been easy to 



