2 BULLETIN 675, U. S. DEPARTMENT OF AGRICULTURE. 



The data in the bulletin were obtained, for the most part, on the 

 high summer range of the Manti National Forest in central Utah, 

 where the conditions influencing erosion are similar to those prevail- 

 ing on many of the mountain ranges in Utah, Wyoming, Idaho, 

 Nevada, Arizona, and New Mexico, and to some extent in other 

 "western States. 



To complete the study "will require a number of years, but the data 

 already available on the decrease in the productivity of the soil 

 resulting from erosion, the increase in the difficulty of revegetating 

 the lands as erosion and soil depletion advance, and the influence 

 of range preservation in preventing destructive erosion are of so 

 much importance that their publication, together "with the accom- 

 panying recommendations, should stimulate closer observation on 

 the part of those in charge of the range lands throughout the West 

 and bring about improvements in the management of these lands, 

 which, in view of the needs of the Nation, should not be deferred. 



DAMAGE CAUSED BY EROSION. 



Every drop of rain that falls on more or less exposed soil has the 

 power of removing soil particles, and with them the soluble salts 

 essential to plant growth. Where the vegetative cover on a water- 

 shed has been largely destroyed the washing off of the surface soil 

 may remove infinitely more decomposed vegetable matter and solu- 

 ble plant food in a single season — indeed during one violent storm — 

 than would be deposited by the decay of the vegetation in years. 

 More than this, the resulting erosion, with its rush of water and 

 debris, frequently ruins the lands where the debris is deposited and 

 puts out of commission roads, trails, power plants, and other im- 

 provements. In many localities loss of property from this source 

 has been appalling. 



The greatest damage from erosion on range lands occurs where the 

 areas have been badly overgrazed and the ground cover destroyed 

 or seriously impaired. Before the ranges had been overstocked and 

 the ground cover impaired, erratic run-off and erosion were practi- 

 cally unknown. After the breaking up of the vegetative cover in 

 the early nineties, however, many streams originally of steady year- 

 long flow and teeming with trout became treacherous channels with 

 intermittent flow through which the water from rainstorms was 

 plunged, or rose and fell according to the size and frequency of the 

 storms and carried so much sediment in the water that fish and 

 similar life could not exist. (PL I, fig. 1.) 



The damage is not confined merely to the decrease in the forage 

 yield on the range lands eroded and to the silting over of adjoining 

 agricultural land to which the torrential floods carried the debris; 



