28 



A NATIONAL PLAN FOR AMERICAN FORESTRY 



States exerts a major influence on watershed protection and that an 

 additional one fifth exerts a moderate influence. 



THE MOST CRITICAL CONDITIONS 



The most critical watershed conditions resulting from the clearing 

 of land for agriculture are the Mississippi bluff and silt-loam uplands, 

 the piedmont and upper coastal plain in the Atlantic and Gulf 

 drainages, and the Central State farm lands of the Mississippi Basin. 



The bluff and silt-loam upland area, approximating 20 million 

 acres, extends from New Orleans to St. Paul. Its wind-blown silt- 

 loam soils contribute more to the Mississippi silt problem than any 

 other area of equal size. A high percentage of the area, in some 

 cases 40 percent of entire counties, is being rapidly destroyed for 

 agriculture by erosion. It is an enormous contributor to the serious 

 Yazoo flood problem, where experimental tests have shown a run-off 

 ratio between cultivated fields and forest of 127 to 1. 



50 



100 150 200 



MILLION ACRES 



250 



300 



FIGUKK 16. One half of the total area of forest land of 615 million acres is classified as having a major water- 

 shed influence and nearly three fourths as having a major or moderate influence. This indicates only 

 in part, however, the value of the forest for watershed protection. 



Erosion and floods are hardly less serious on the much larger pied- 

 mont and upper coastal plain extending from the Potomac into 

 Mississippi. Largely as a result of erosion, at least 8% million acres 

 have been abandoned for agriculture in the past 20 years and trends 

 indicate a total of 12 million by 1950. 



The Central States farm land area, including parts of 10 States 

 from West Virginia and Ohio to eastern Kansas and Nebraska, makes 

 another large contribution to the Mississippi Kiver flood and silt 

 problem. The abandonment of 15 million acres of farm lands in the 

 area of most critical erosion conditions seems to be only the beginning. 



The watersheds of the northeastern drainages derive their chief 

 watershed importance as the source of the municipal supplies of the 

 great Eastern cities from Boston to Baltimore. The forests most in 

 need of improvement are in the southern half of the area. 



The Appalachian Mountain ranges feed the Mississippi and its 

 tributaries, and the Atlantic coast and Gulf rivers from the Delaware 

 to the mouth of the Mississippi. Heavy and frequently torrential 



