The increasing horse numbers, 25 percent increase 

 in the 1974-1976 period, are resulting in heavy range 

 use in some places. Concerns are mounting about the 

 impacts of these animals upon vegetation and soils 

 resources and their competition with other grazing 

 animals, both domestic and wild. The Public Range- 

 lands Improvement Act of 1978'' may offer some 

 relief because it provides improved measures for the 

 two agencies to dispose of surplus animals, i.e., ani- 

 mals in excess of the sustained grazing capacity of the 

 range. 



Use by wildlife. — In addition to providing forage 

 for livestock and wild horses and burros, the Nation's 

 range, as stated previously, also furnishes food and 

 cover for millions of wild animals. No reliable 

 national population data are available for most wild- 

 life species, or even such common big game animals 

 as deer and elk. However, Wagner'^ has summarized 

 recent population estimates by the fish and game de- 

 partments of the western States (table 5.6). 



These estimates, even though incomplete, indicate 

 big game populations in excess of 4 million animals 

 for the 1 1 western States. Present numbers, except for 

 deer, are far lower than for the populations believed 

 to have been in the area when Columbus landed in 

 the New World. Wagner speculates that the pre- 

 Columbus populations were: bison, 5-10 million; 

 pronghorn 10-15 million; bighorn sheep, 1-2 million; 

 mule deer and blacktail deer; 5 million; and elk, 

 2 million. 



An estimated 1 1 million animal unit months 

 (AUM's) of forage are required to sustain Wagner's 

 present populations.'^ Data developed for this report 

 indicate that as much as 154 million AUM's of her- 

 bage and browse are currently available for wild rumi- 

 nants (e.g. deer, elk, moose, etc.) in the 1 1 western 

 States. This is far more than that required to meet the 

 forage requirements of the populations listed by 

 Wagner. 



Wildlife use of the Nation's forests and rangelands 

 is discussed in further detail in the wildlife chapter of 

 this report. 



Nongrazing Uses 



While the common product from range is forage 



"95th U.S. Congress. Public Rangelands Improvement Act. 

 Public Law 95-514. 1978. 



"Wagner, Frederic H. Livestock grazing and the livestock 

 industry. Chapter 9, p. 121-149, in Wildlife and America; Contri- 

 butions to an understanding of American wildlife and its conser- 

 vation, H. P. Brokaw, editor. Council on Environmental Quality. 

 1978. 



"An animal unit month (AUM) is the amount of forage 

 required by a 1,000-pound cow or its equivalent in 1 month. 



for livestock, big game, and other herbivores, the 

 range does yield many other products. Rangelands 

 are important sources of coal, oil, uranium, and other 

 economically significant minerals. They provide sites 

 for many forms of outdoor recreation such as hunt- 

 ing, hiking, off-road vehicle use, birdwatching, flower 

 viewing, and rock hounding to name a few. They also 

 serve other purposes described below. 



Commercial plants. — Some old and well-estab- 

 lished range uses are assuming far greater importance 

 now than they did in the past. For example, the har- 

 vesting of pinyon nuts was once largely the activity of 

 some Indian tribes of the Southwest. Now it is also a 

 popular recreational activity for many people. Juni- 

 per has traditionally provided fenceposts and, along 

 with pinyon, firewood for ranchers. Now with esca- 

 lating costs of fuel oil and natural gas, urban dwellers 

 are also demanding juniper and pinyon for use as 

 fuel. The demands are so great in some areas that 

 supplies must be closely managed. 



In 1910, about half of all United States rubber 

 came from guayule, a range shrub of arid lands in 

 Texas and Mexico. The wild guayule stands were 

 soon depleted and the hevea rubber tree of the East 

 Indies became the source of natural rubber. But in 

 World War II, when the United States lost more than 

 90 percent of its rubber supplies, attention focused 

 once again upon guayule as a source of rubber. Three 

 million pounds of rubber for the war effort were pro- 

 duced from the shrub. After the war, the Nation re- 

 turned to the hevea rubber tree and to petroleum as 

 its sources of rubber.'^ Recent research, however, 

 shows that rubber production in young guayule 

 plants can be increased from two to six times by 

 spraying with mixtures of chemicals called bioregula- 

 tors. Should these developments prove to be com- 

 mercially feasible, some 5 million acres of arid range- 

 land in New Mexico, Arizona, California, and Texas 

 may be involved in the production of guayule 

 rubber."' 



Other research has led to pilot-scale production of 

 petroleum from range plants of the genus Euphor- 

 bia.^'^ As much as 25 million acres of dry rangelands 

 could be managed as "hydrocarbon plantations," if 

 the pilot tests prove to be economically successful. 2' 



'* National Academy of Science. Guayule: an alternative source 

 of natural rubber. 80 p. 1977. 



I' Dean, J. Paul. New method increases rubber from guayule. 

 Agr. Res. 27(2): 810, illus. 1978. 



'"Calvin, M. Energy and materials via photosynthesis. P. 231- 

 259 in R. Buvet and M. J. Allen, eds. Living systems as energy 

 converters. North Holland Publishing Co., New York. 1977. 



-' Pimental. David, Donald Nafus, Walter Vergara, Dan Papaj, 

 Linda Jaconetta, Marty Wulfe, Linda Olsvig, Kerry French, Mark 

 Loye, and Ellen Medoza. Biological solar energy conversion and 

 U.S. energy policy. Bioscience 28(6): 376-382. 1978. 



167 



