Our Livini; Resources — Human Influences 



42.1 



Precipitation and snowmelt pH levels were 

 not low enough to mobilize aluminum (Do/ier 

 et al. 1987). Bradford et al. (1992) found that 

 present pH levels in Sierran lakes and streams 

 are not sufficient, directly or through aluminum 

 mobili/ation. to affect indigenous amphibians. 



The measured reductions in sulfur loading 

 and decrease in frequency of low-pH storm 

 events suggest that reduced pollutant emissions 

 may be having a positive effect on the air qual- 

 ity of the southern Siena Nevada. Continued 

 monitoring and further research will be needed 

 to determine if this trend will continue, given 

 the tremendous rate of population growth in 

 California. 



References 



Blanchard. C.L.. and K.A. Tonnesen. 1993. Precipitation- 

 chemistry measurements from the California Acid 

 Deposition Monitoring Program. 1985-1990. 

 Atmospheric Environment 27A( 1 1): 1755- 1763. 



Bradford. D.F.. C. Swanson. and M.S. Gordon. 1992. 

 Effects of low pH and aluminum on two declining 

 species of amphibians in the Sierra Nevada. California. 

 Journal of Herpetology 26:369-377. 



Dozier. J.. J.M. Melack, D. Marks. K. Elder. R. Kattelman. 

 and M. Williams. 1987. Snow deposition, melt. runoft\ 



and chemistry in a small alpine watershed. Emerald Lake 

 basin. Sequoia National Park. Final report to California 

 Air Resources Board. Contract A3- 106-.^2. 155 pp. 



Landers. D.H.. J.M. Ellers, D.F. Brakke. W.S. Overton, RE. 

 Kellar. M.E. Silverslein. R,D. Schonbrod, R.E. Crowe. 

 R.A. Linthurst, J.M. Omemik, S.A. Teague. and E.P. 

 Meier. 1987. Characteristics of lakes in the western 

 United States. Vol. 1. Population descriptions and physi- 

 co-chemical relationships. U.S. Environmental 

 Protection Agency EPA-60n/3-S6/054a. 1 76 pp. 



Sickman. J.O.. and J.M. Melack. 1989. Ch;u-actenzation of 

 year-round sensitivity of California's montane lakes to 

 acidic deposition. Final report to California Air 

 Resources Board. Contract A5-203-32. 104 pp. 



Temple. RJ., G.H. Riechers. and RR. Miller. 1992. Foliar 

 injury responses of ponderosa pine seedlings to ozone, 

 wet and dry acidic deposition, and drought. 

 Environmental and Experimental Botany 32(2): 101-113. 



Williams, M.W.. A.D. Brown, and J.M. Melack. 1993a. 

 Geochemical and hydrologic controls on the composition 

 of surface water in a high-elevation basin. Sierra Nevada. 

 California. Lminology and Oceanography 38(4):775- 

 797. 



Williams. M.W.. and J.M. Melack. 1991. Solute chemistry 

 of snowmelt and runoff in an alpine basin. Sierra Nevada. 

 Water Resour. Res. 27:1575-1588. 



Williams. M.W., J.M. Melack. and D.A. Everson. 1993b. 

 Export of major ionic solutes from two subalpine water- 

 sheds before and after fire. Poster presented at Annual 

 Meeting of American Geophysical Union. San Francisco. 

 CA. 



For further information: 



David M. Graber 

 National Biological Service 

 Sequoia and Kings Canyon 



Field Station 

 Three Rivers. CA 9327 1 



Approximately 45% of the U.S. land area is 

 used for agricultural purposes, with 191 

 million ha (472 million acres) in cropland and 

 238 million ha (587 million acres) in range or 

 pasture (Knutson et al. 1990). American agri- 

 culture has become the most productive in the 

 world based on technology and increased spe- 

 cialization. Energy, machinery, agrochemicals. 

 and irrigation are principal components of mod- 

 em American agriculture, all of which poten- 

 tially affect farm and off-farm environmental 

 quality. In addition, government policies have 

 pervasively affected U.S. agriculture, often pre- 

 cluding producers from responding to changing 

 market conditions or affecting adoption of farm 

 practices that potentially improve environmen- 

 tal quality (National Research Council 1989; 

 Reichelderfer 1990). 



Energy and technology have propelled 

 American agriculture from pioneering conver- 

 sion of the landscape to intensive, high-yield, 

 monocultural production. The composuion of 

 agriculture in terms of farm numbers, size, and 

 methods of production have changed dramati- 

 cally throughout this century. The effects of the 

 agricultural industry on the diversity, distribu- 

 tion, and abundance of wildlife continue to be 

 profound. 



Larger, more economically efficient produc- 

 ers that could tolerate smaller profit margins 

 have absorbed the assets of smaller, less suc- 

 cessful operations. In 1991 the U.S. human pop- 

 ulation on farms was less than one-tenth of what 

 it was in 1920 (Haynes 1991), As the number of 



farms decreased by two-thirds during this same 

 period, farm size increased. In response to 

 fewer farms and the need to increase production 

 efficiency, fields have become larger, crop 

 diversity has decreased, crop rotation patterns 

 have become simpler and less frequent, and 

 agrochemicals play a major role in crop produc- 

 tion. Over the last 30 years, these elements have 

 had significant effects on environmental quality 

 within agricultural ecosystems. 



The Conservation Title of the Food Security 

 Act of 1985. commonly referred to as the Farm 

 Bill, was fomiulated in a time of commodity 

 surpluses, economic stress within the agricul- 

 tural community, and increasing public concern 

 about environmental quality. The Conservation 

 Reserve Program (CRP). a cornerstone of the 

 1985 Farm Bill, was enacted to remove highly 

 erosive cropland from production. This legisla- 

 tion reflects an effective integration of econom- 

 ic support to the agricultural community with 

 environmental policies advocated by a strong 

 coalition of organizations representing a wide 

 spectrum of the American public. The CRP has 

 provided substantial benefits to wildlife popula- 

 tions across the nation. To appreciate the CRP's 

 significance to wildlife, we must remember that 

 tremendous changes in agriculture have influ- 

 enced the abundance and quality of habitat in 

 this century (Soil and Water Conservation 

 Society 1994). 



World War II. for example, brought an 

 increased demand for American agricultural 

 products. New technologies adopted in the 



Agricultural 

 Ecosystems 



by 



Arthur W. Allen 



National Biological Service 



