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498 composition processes IS available (Sokol and Klein, 1975). Elsewhere, despite diligent monitoring, no trace of silver attributable to cloud seeding, or impact of such silver, has been found. It has been hypothesized that addition of silver to near impact threshold concentrations might retard de- composition and allow a higher accumulation of organic matter in the soil. Whether such accumulation actually occurs, or whether it would be harmful if it did occur, has not been determined. The possible emergence of silver tolerant microbiotic ecotypes in naturally or artificially enriched areas has not been investigated. At any rate, evidence of gross inhibition of decomposition in naturally enriched soils under field conditions is lack- ing. The time scale of accumulation and migration of silver from soil to plant tissues and back appears to be such that assimilation of imposed silver iodide or other silver-bearing pollutants to the naturally prevailing forms of this element would be rapid in relation to the accumulation itself and would determine the forms of silver actually present and active in the soil. Only the amount of silver dosage, not its initial chemical form, would be significant. 3. Human responses to the environmental impacts of precipitation management The scope of the environmental movement has not stopped at the limits of the natural environment but has come to embrace impacts upon mankind. In the environmental sense, the focus of concern is not upon the principal actors-the cloud seeders and their clients -but upon persons and institutions indirectly affected and upon bystanders. Sociologists and political scien- tists have evinced also a lively interest in understanding the behavior of persons who support or oppose pre- cipitation management at all levels, from local to national. 1) SOCIAL INSTITUTIONS With minor exceptions, preCIpItation management is not seen as altering the structure or functions of so- cietal institutions, since these are already well adapted to dealing with new services. Attention has been di- rected mostly to considering how existing institutions will interact with precipitation management and what shape they will give it. 2) REGULATORY MEASURES The most characteristic response to potential adverse impacts takes the form of regulatory measures aimed at mitigating them. Since precipitation stimulation during a flood would be disadvantageous, as indeed would be any action tending to aggravate a climatic extreme, such actions are prohibited in all jurisdictions that regulate weather modification operations. In practice, these prohibitions extend to a number of environmental hazards including avalanches, hail, severe local storms, floods, adverse effects on crops or agricultural fieldwork, and even interference with the county fair. Vol. 58, No.6, June 1977 3) ADAPTATION TO UNDESIRABLE EFFECTS Another response is adaptation to a possible unde- sirable effect such as an increase in plant diseases. Since precipitation management is not known to present any hazards not already the concomitants of natural weather occurrences, adaptive strategies (e.g., spraying to control mites) are already developed to varying degrees. Experi- ence to date suggests that widespread and prolonged application of weather modification will be accompanied by an insistence on further study of potential unde- sirable effects and means of coping with them, but future specific responses outside the existing pattern are not now identifiable. For example, a review by the California Department of Highways of probable re- sponses to snowpack augmentation indicated that no change in current practices respecting snow clearance and associated safety activities is anticipated. In instances where weather modification for the bene- fit of one interest imposes an identifiable undesirable effect on another in terest, compensation has been pro- posed and discussed in principle (e.g.. Taubenfeld, 1968), but the manner in which degrees of causality and liability might be established in practice remains to be deterrilined. The most likely arena for the development of this response is that of agriculture, where adjacent crops may benefit from moisture, or dryness, at differing stages of their development. 4) COLLATERAL BENEFITS Responses to collateral benefits from environmental im- pacts are also likely to follow strategies already es- tablished for dealing with the vagaries of the weather, and only the degree and frequency of such responses rather than their nature are likely to change. For ex- ample, if rain stimulation for the benefit of wheat lands were to increase the carrying capacity of nearby wildlife ranges, the number of hunting licenses issued annually might change, but the general strategy of game manage- ment would remain unaltered. Similar responses to col- lateral benefits are to be expected throughout the net- work of water uses. 5) SUMMARY The only novelties likely to be manifested as a result of widespread and prolonged weather modification are extension of related environmental research and de- velopment of principles for the compensation of in- terests negatively affected by actions undertaken m the name of the general welfare. 4. Environmental impact of Skywater activities More than 15 programs of field experimentation in- volvim' cloud seeding have been carried out since 1965 under C'Skywater sponsorship, ranging from brief expedi- tion type efforts to 4- and 5-year pilot projects in Colo- rado and North Dakota. Further experimentation is scheduled in the High Plains area and in the central Sierra Nevada. Current policy has required that the im- mediate impacts of these activities, as well as the impli-