Historical notes and effects of grazing 

 Leo A. Hanna 



The area under consideration is Bridger Basin, a distinct 

 physiographic and topographic unit of a portion of the Green 

 River valley of southwestern Wyoming. It is characterized by 

 a terrace and escarpment topography on the nearly horizontal 

 Eocene beds. To the casual observer it has the general aspect 

 of a sagebrush plain, but on closer inspection it presents not 

 only sagebrush-rabbit brush communities, but also those of the 

 gravel and the adobe flats, dry washes, fixed sand dunes, bad- 

 land fronts, and gravel escarpments. 



It is often maintained that the present flora of this section 

 is very different from that found here when the emigrants of the 

 fifties and sixties of the last century passed through. The sup- 

 posed change has been accounted for in various ways, as the 

 result of overgrazing or as the outcome of climatic changes. Of 

 course there has been some overgrazing and ruderals have 

 gained a foothold in many places as along railroads, highways 

 and streams. In most cases, however, their appearance indicates 

 disturbance of the soil by construction work, or by flooding and 

 the incident erosion and deposit. It is the author's opinion that 

 much of the supposed change is to be accounted for by seasonal 

 variations. Dr. Aven Nelson, eminent botanist of the West, 

 crossed the Red Desert on a tour of inspection (1930) for the 

 express purpose of comparing and studying the changes that had 

 taken place in the vegetation during the last thirty years. After 

 a careful study of his original notes (1900) and thoughtful con- 

 sideration of the problem from all angles, he reached the con- 

 clusion that there has been no appreciable change in spite of the 

 fact that vast numbers of sheep browse on the forage of the 

 area. 



This contention is sustained by a study of the earliest histor- 

 ical notes available. During June, 1833, John B. Wyeth and 

 party camped on the Green River while exploring its valley. On 

 July 4 he reports in his diary the crossing of Ham's Fork. Town- 

 send's narrative of the expedition, 1833-34 makes the following 

 allusion to the vegetation: 



"On the 14 of June we left the Sweetwater river and pro- 



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