SUSTAINED ANNUAL YIELD 



821 



relatively small amount of timber to be cut for lumber and a vast 

 amount of tree growth on hand, of inferior quality and of small size, 

 suitable for pulp, perhaps, but not for construction purposes. 



At the present time, in the United States, forest fires burn over an 

 average of about 8,000,000 acres a year. It may be said confidently 

 that, excepting the wet swamp lands, not 5 per cent of the slash lands 

 of the United States are unburned. 



These figures indicate that little can be expected in the way of relief 

 from a timber shortage from growth from cutover lands. This may be 

 brought out by a graph (fig. 1) indicating growth, of forest and of 

 population, and cut of timber in the United States. 



The upper curve — lumber cut — is taken from the best data available. 

 The solid line indicates the actual amount of timber cut in the United 

 States since 1880. It has increased steadily with the growth of popu- 

 lation, and may be expected to continue to do so until the main bodies 

 of virgin supplies are exhausted which will come about in 1970. From 

 that time supplies must come from second growth. 



SO-f-O 2060 



The amount of second growth material growing each year is indicated 

 by bottom curve "annual growth." If proper forestry measures are 



