156 



A NATIONAL PLAN FOB AMERICAN FORESTRY 



prior to 1900 has become forest. Relatively less of the land aban- 

 doned in each succeeding decade since 1900 is now in forest. Not 

 even all of the 31,000,000 acres (see table 4) which has gone put of 

 use for crop and livestock production in the past two decades is still 

 available for reforestation. It is probable that a substantial part of 

 the 21,000,000 acres which has gone out of agricultural use since 1920 



FIGUEE 1. The percentage decrease in agricultural land from the peak to 1930. 



is available for reforestation and a portion of the 10,500,000 acres 

 which went out of use for crop and pasture in the decade 1910 to 1920 

 is available. The rate at which these acreages will grow up naturally 

 to trees will depend upon a number of factors, including the quality 

 of the land, the number and species of seed trees, and protection from 

 fire and other injury. 



