THE ECONOMIC IMPORTANCE OF FORESTS 



497 



Benefit to Soil. The early settlers regarded the forests as the 

 enemy to agriculture and so they were, in so much as some clear- 

 ings had to be made to make room for the farms, but in a larger 

 sense, the forests are a distinct benefit to the soil. Erosion, the 

 washing away of soil by rain, is one of the worst enemies of ag- 

 riculture and this is prevented by the forest areas, whose roots 

 hold back the earth and whose leaves protect the surface. Fur- 



FOREST PRODUCTS IN 1907. 



CLASSES 



FIREWOOD. 



LUMBER AND SHINGLES 



POLES, POSTS. AND RAILS. 



HEWED CROSS-TIES 



COOPERAGE STCT,K 



PULP-WOOD. 



ROUND MINE TIMBERS 



DISTILLATION WOOD... 



FOREST MATERIAL REQUIRED 

 BILLIONS Or CUBIC FEET 



Fig. 157. Uses of Lumber. From Smith's Commerce and Industry. 



thermore, the organic matter (humus) which collects on the forest 

 floor, supplies an essential element to all fertile soils. 



In some areas, the forests perform another function in pre- 

 venting the spread of wind-blown sand over fertile areas which 

 are thus saved for use. 



Effect of Forests on Climate. While this may not rank with 

 the two preceding in importance, yet it is certain, that by its 

 retention of moisture, forests do modify the climate over large 

 areas and apparently influence local rain-fall as well. To a less 



