Fiinc 



fixed nitrogen, either natural or synthetic (NRC-17). An- 

 other is the possibihty of developing synthetic versions of 

 natural "growth regulators" that could speed the develop- 

 ment of plants and animals. Changing the rates of de- 

 velopment might shorten the time required for a crop to be 

 ready for market, thereby increasing yields (AGR). 



The cultivation of animal species is potentially as sig- 

 nificant as the cultivation of plants. While it is sometimes 

 asserted that animal culture is less efficient than plant 

 culture in meeting total nutritional demand, nearly two 

 thirds of the world's agricultural land is in pasture or range 

 suitable for animals, and 60 percent of that land would not 

 support the cultivation of plants (AAAS-8). Again, ad- 

 vances in scientific techniques, particularly in genetic 

 engineering and embryological research, are now making 

 and promise to continue to make significant contributions 

 to increasing the effectiveness and efficiency of animal 

 husbandry (AAAS-8; AGR). 



CONTROLLING PESTS 



In addition to developing new or modified agriculturally 

 relevant plant and animal strains, controlling agricultural 

 pests is a mechanism that can be invoked to increase 

 product yields. The control of pests, whether they are 

 plant, animal or microbial, is a critical aspect of the 

 efficiency of agriculture. It is estimated that 30-40 percent 

 of the world's crops are lost to disease between planting 

 and harvest, and another 10 percent is lost in postharvest 

 storage due to pests (NRC-6). Again, scientific and tech- 

 nological advances can help on several levels. On the 

 epidemiological level, sophisticated analytical method- 

 ologies are being used to understand patterns of the spread 

 of disease and the nature of biological susceptibility. On 

 the farm level, integrated pest management (1PM) is gain- 

 ing in use. IPM involves fitting together information about 

 the biology of pests, the environment, and the status of the 

 host to obtain maximal results from the application of 

 biological (natural enemies, parasites, and predators) and 

 chemical control methods. The technique not only re- 

 duces the load on the environment from pesticides, but is 

 also cost-effective (NRC-6). 



One approach used in IPM involves the selective use of 

 "multilines." selectively bred variations of plants that are 

 similar in yield but different in their relative resistance to 

 diverse pests. The tendency in selective breeding, par- 

 ticularly of plant species, traditionally has been toward 

 seeking greater genetic uniformity, standardizing yields 

 but increasing the susceptibility to pests. However, there 

 is no antibody response to infection in plants; disease 

 resistance is purely an inherited trait and can only be 

 conveyed genetically. Therefore, developing multilines 

 can be used to slow the spread of such infections as wheat 

 rust by decreasing the proportion of plants in a given area 

 that are susceptible to particular varieties of the disease. 

 The disease problem will never be completely solved; 



tioiial Area Pioblcms. Opportunities, and Constraints 75 



disease spread appears to vary according to the natural 

 resistance offered by hosts and is continually changing, 

 but, it can be controlled. Thus, constant attention to plant 

 disease spread is needed (NRC-6). In providing that atten- 

 tion, however, it should be remembered that natural epi- 

 demics almost never occur; major plant diseases are the 

 result of human transfer of plants from one biosystem to 

 another. Therefore, understanding the nature of the sys- 

 tematic relationships of plants to their environments is a 

 major aspect of the control of agricultural pests and will 

 require additional activity in the coming years (NRC-6). 



PREPARING FOR CLIMATIC AND ENVIRONMENTAL 

 STRESSES 



Environmental stresses other than pests and predators also 

 threaten agricultural yields. There is no doubt that the 

 world is undergoing some significant changes in climatic 

 patterns, although the direction in which those changes 

 are tending and the causes, whether they are natural or 

 human induced, are still open to debate. The immediate 

 effects are to upset patterns of cultivation by changing 

 rainfall levels, temperature, and nutrient supplies. Those 

 changes in turn alter yield patterns and, thus, aspects of 

 the interrelationships of agricultural products, such as the 

 availability of animal feeds. Work continues on using 

 genetic engineering techniques to "climate-proof" plants 

 and animals, improving their ability to withstand environ- 

 mental stresses. That approach could not only reduce the 

 exposure of plants and animals to normal hazards, but 

 could also expand the range of lands in which cultivation 

 is possible (AGR). 



In the long term, the effects of climatic changes may be 

 even more dramatic than they are currently. For example, 

 continued burning of fossil fuels and the conversion of 

 tropical forest to agriculture, as discussed in the Natural 

 Resources section of this chapter, is likely to have major 

 effects on carbon dioxide levels in the atmosphere 

 (NRC-5). Such other stresses as pollution, particularly 

 the "acid rain" that results from the use of fossil fuels, 

 affect the biosphere and hence agriculture in key ways 

 (AGR; ENVIRON). Much remains to be learned about 

 precisely what the effects of such stresses and changes on 

 agriculture are likely to be and how they might be allevi- 

 ated. The lack of knowledge raises the need for additional 

 scientific and technological efforts directed toward, first, 

 identifying the potential problems and, second, devising 

 counteractive measures. 



GETTING AGRICULTURAL PRODUCTS TO 

 MARKET 



A major but generally disregarded aspect of efficiency in 

 agriculture is the processing and distribution system. 

 Postharvest losses in the United States cost an estimated 

 $30 billion annually, and in some developing countries 



