WHAT THE FORESTS DO FOR US 15 



the foot of the steep slopes badly cut by gullies two or 

 three feet deep formed during a heavy thunder shower. 

 Such lands, of course, should never have been cleared, 

 because if the slopes are so steep and the soil so heavy 

 that erosion is bound to occur, the best use to which 

 such land could be put is the raising of repeated crops 

 of timber. 



The question of erosion in this country is one of 

 great importance since no less than two hundred square 

 miles of fertile farm lands are annually damaged by 

 the action of erosion and flood. 



In checking the force of drying winds, forest belts or 

 windbreaks also play an important role. In certain 

 parts of the Middle "West, windbreaks are almost in- 

 dispensable because the hot drying winds that some- 

 times sweep up from the South have been known to 

 wilt a splendid field of grain overnight. Had wind- 

 breaks been planted every quarter of a mile across the 

 track of the prevailing wind, the force of these winds 

 would have been greatly checked; water vapor would 

 have been added to the moving air currents, and the 

 force and drying effect of these damaging gales would 

 have been greatly reduced. Investigators claim that 

 twenty per cent of the agricultural land of the level 

 Middle West could be advantageously planted with 

 windbreaks running east and west and on account of 

 the protection afforded by these belts the remaining 

 eighty per cent of farm land would produce as much 

 as the total area at the present time. The beneficial 

 effects of these windbreaks in diminishing evaporation 

 from plants and soil are clearly felt one rod to their 

 lee for every foot in height. That is, a windbreak ten 

 feet high would exert a decided influence in checking 

 evaporation one hundred and sixty feet to the leeward. 



