patterns of distribution for the herbivore populations upon which it 

 preys. "Clean" monoculture for field or forest crops may become 

 ecologically unstable because the populations of grazing animals, 

 particularly insects that can be supported by the extensive food source, 

 usually lack the predatory control that exists in a more heterogeneous 

 system. A hopeful approach to the regulation of agricultural pests is 

 the development of pest management systems which integrate 

 chemical, biological, and cultural practices including genetic selection, 

 mixed crop plantings, predator introductions, biodegradable 

 pesticides, attractants, repellants, and hormonal chemicals. 



4. Human Ecology Human ecology is primarily concerned with the effect ofthe living and 



nonliving environment on man. His responses to this environment 

 may be physiological, psychological, or behavioral. Urban ecology is 

 the study of human settlements, the habitat of man. Evidence is 

 accumulating that people respond to crowding, to architectural design, 

 and to other aspects of their urban environment in important ways. For 

 example, the necessity to destroy portions of the Pruitt-Igo housing 

 complex in St. Louis seems directly attributable to a building design 

 that failed to provide an appropriate degree of family privacy. 



When men live in small groups as primitive cultivators, nomadic 

 herders, or hunters, their ecological relationships are little different 

 from those of many other animals of similar size and trophic demand. 

 But the concentration of humans in urban societies is unique. While 

 other large animals which are spatially packed move continuously 

 over large areas to acquire food (e.g., bison herds), food must be 

 imported to cities and wastes must be removed. 



Providing nutrients thus becomes a vast, complex set of operations 

 involving the importation of large quantities of food derived from 

 distant crop lands, ranges, and fisheries. Industrial man uses fossil 

 energy to increase the efficiency of conversion of solar energy to a 

 desired food and to increase the yield of monocultural crops, herds and 

 fisheries. Fossil energy is used to import fertilizers, prepare pesticides, 

 and run heavy equipment for tilling and harvesting. But industrial 

 man's use of selected, high-yield crops and livestock may so alter the 

 original composition of the ecosystem that the system's very stability 

 is threatened. Wherever these changes are excessive, the instability of 

 the ecosystem becomes obvious, as those who lived in the "dust bowl" 

 of the 1930's will remember. Improved management has, for the 

 moment at least, reduced the sensitivity of prairie systems to such 

 changes. But maintenance of productive systems on prairie sites 

 exacts a high cost in fossil or nuclear energy. 



5. Relating Ecological 

 Values to Societal 



Evaluating trade-offs for alternative, often competing, uses of land is 

 ecologically difficult because the market value of ecological effects, 

 both acute and chronic, cannot be easily determined. Assessing 

 Needs ecological effects by traditional cost/benefit analysis is therefore not 

 sufficient. 



One method used to calculate the monetary value of natural 

 ecosystems employs an "Energy based" technique. Basically money 



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