42-t 



Human Influences — Our Livint; Rcxonrces 



Percentage of county 



I — I 1.00 or less 



I — I 101 to 5 GO 



mm 5.01 to 10.00 



^ 10.01 to 20.00 



^ 20.01 to 30.00 



nn NoCRP 



post-war period reduced production costs and 

 further escalated farm output. Tractors and fami 

 machinery became more powerful and efficient. 

 Time and energy savings decreased the amount 

 of human labor needed to work larger fields. 

 Advances in biological and chemical technolo- 

 gies further increased agricultural efficiency 

 and crop yields. The use of nitrogen fertilizer 

 increased from 197 million metric tons (217 

 million tons) in 1940 to 6,765 million metric 

 tons (7.459 million tons) in 1970 (Haynes 

 1991 ). By the early 1970\. crop yields had sky- 

 rocketed to new records. 



American agriculture entered the world mar- 

 ket in the 1970"s in response to increased glob- 

 al demands for agricultural products. American 

 farmers expanded production by cultivating 

 existing croplands more intensively and bring- 

 ing new, less fertile and more fragile lands into 

 production. The 1980"s arrived with the farm 

 industry in crisis due to overproduction, 

 increased costs for fuels and fertilizers, elevated 

 interest rates, declining land values, and 

 decreased demand for export sales. The agricul- 

 tural economic predicament, as well as height- 

 ened public concern about environmental quali- 

 ty, set the stage for the 1985 Farm Bill and 

 establishment of the CRP. 



Agricultural Effects on Wildlife 

 Habitat 



The effects of modem agriculture on wildlife 

 are indisputable, ranging from habitat elimina- 

 tion to long-term effects of agrochemicals on 

 water quality and reproductive success of 

 ground-nesting birds (Capel et al. 1993). 

 Habitat diversity in agricultural ecosystems has 



Fig. 1. Percentage of county area enrolled in the Conservation Reservation Program (CRP) 

 through July 1992. 



declined drastically as a consequence of the 

 elimination of hay and pasture needed by draft 

 animals and a shift to crop monocultures. In 

 many regions, wetland drainage, consolidation 

 of fields and farms, and elimination of 

 fencerows and idle areas have reduced habitat 

 diversity even further, thereby diminishing the 

 ability of agricultural ecosystems to sustain 

 viable populations of wildlife. The amount of 

 undisturbed grass-dominated cover and non- 

 cropped areas has decreased, resulting in lower 

 availability of habitat and higher losses to 

 predators for many nongame and game species 

 of wildlife. In many agricultural regions, crucial 

 wildlife habitat components such as undis- 

 turbed grassland have become dissected into 

 small, isolated patches, or spatially segregated 

 tracts. Increased agrochemical use has been 

 implicated in the long-term decline of species 

 such as the northern bobwhite {Colinus virgini- 

 aniis). 



Monocultures, with minimal rotations 

 between crops, have accelerated soil erosion 

 and led to a greater dependence on chemical 

 fertilizers and pesticides (Bender 1984) result- 

 ing in surface and groundwater contamination 

 (Ribaudo 1989). Larger, heavier equipment 

 used for tillage, planting, application of agro- 

 chemicals, and harvesting contributes to 

 increased soil compaction and decreased soil 

 tilth (suitability), further contributing to ero- 

 sion. Agriculture has become the largest single 

 nonpoint source of water pollution, delivering 

 not only soil particles but also absorbed and dis- 

 solved nutrients and pesticides (National 

 Research Council 1989). 



The Conservation Reserve 

 Program (CRP) 



About 14.7 million ha (36.4 million acres) 

 were removed from production for a minimum 

 of 10 years during the 1 2 sign-up periods of the 

 CRP (U.S. Department of Agriculture 1993). 

 The percentage of each county area enrolled in 

 the CRP is illustrated in Fig. 1. Grasses repre- 

 sent the vast majority of cover established on 

 retired acres (Table). The most significant ben- 

 efit to wildlife from the CRP is the more than 13 

 million ha (32 million acres) of grass inter- 

 spersed with lands remaining in production. 

 This grass cover has enhanced the quality and 

 distribution of habitat for nongame and game 

 species in both tenestrial and aquatic ecosys- 

 tems. To document CRP-derived benefits to 

 habitat quality, a cooperative study between the 

 International Association of Fish and Wildlife 

 Agencies and the U.S. Fish and Wildlife Service 

 was initiated in 1987 (Fanner et al. 1988). 



From 1987 to 1993 fish and wildlife agency 

 personnel from 31 states collected vegetation 



