6 THE PRINCIFLKS OK HANDLING WOODLANDS 



has been the disturbance of stream flow and the erosion of 

 the soil. Forest destruction has already caused a damage 

 of many millions of dollars, by silting up navigable rivers 

 and reservoirs, b\- causing an increase of spring floods 

 and a deficiency of water in the summer, by deposits of 

 rocks, gravel, and sand on agricultural land, by the 

 drying up of the sources of water used for irrigation 

 and for domestic purposes, etc. This damage in the 

 aggregate is so large as to constitute one of the principal 

 causes of the present demand for forestry'. 



If the United States is to have an adequate supply of 

 timber in the future, and if the headwaters of the rivers 

 are to be properlv protected, the practise of forestry is 

 required not only on the public forests, but also on lands 

 now In the hands of private owners. 



Definition of Forestry 



The underlying idea of forestry is continuity of use. 

 Forestry aims to utilize the present product of the forest 

 with the greatest possible econom\', and with profit to the 

 owner, and at the same time to provide for the continu- 

 ance of the forest, and for the production of timber and 

 other forest products in the future. 



Heretofore, lumbering has been the exploitation of a 

 ripe crop of timber, with no intentional provision for the 

 future use of the land for forest growth. The forester 

 regards a forest as a property capable of yielding repeated 

 crops of timber. When a merchantable crop is cut, the 

 forester aims to replace it b\' a new growth, to protect the 



