The suggestion was made in the USSR /25, 51/ that radioecological analyses of insects collected from any given locality might be instrumental in the prospecting and mapping of such deposits, and of areas with radio actively contaminated soil and vegetation. These analyses are simple and rapid, and can be performed on a large scale.
So far we have discussed the role of radioecology in elucidating the bio logical paths of concentration, redistribution, and migration of contaminating radioisotopes in nature. However, in theoretical radioecology consider able attention is given to the effect of ionizing radiations from decaying isotopes on organisms and their communities. The ionizing radiations may act without or within the organism whereby isotopes may occur in organs, cells, and individual molecules of the nucleus or protoplasm.
Results of investigations in this important field are surprisingly contro versial. Without going into detail we shall only mention one view which holds that even the smallest dose of ionizing radiations damages and inhibits the life activities of organisms. Another widely adopted view maintains that the smallest doses of ionizing radiations are biologically inconsequential, that appreciable doses have a stimulating effect, and that detrimental effects appear only when the stimulating doses have been exceeded. In the dosimetric analysis of the effect of any factor in ecological, physiological, physiotherapeutic, and pharmacological practice, the second view prevails, as expressed by the Arndt-Schulz law. This view does not recognize the definitely harmful effect of any dose of ionizing radiation which is claimed by the supporters of the first view. An analysis of these different view points should be approached from another angle, for example by elucidating the mechanism of action of ionizing radiations, which is beyong the scope of this paper. Here, we are essentially interested in the resistance of different organisms to radioactivity. A certain dose of ionizing radiations affects different organisms in different ways, and consequently in any association of organisms, under natural conditions as in a cultivated field, ionizing radiations disrupt previously established relationships. Thus
certain species will develop more successfully than others, although not necessarily as a result of direct stimulation, but rather of the suppression by ionizing radiations of the strongly competitive organisms. These quali tative and quantitative variations in complex interacting populations— bio cenoses— have been adequately demonstrated by experiments /52-54/. Disruption of the ecological relationships between the species leads to the gradual impoverishment of the biocenosis. The number of species is diminished by the disappearance of those that were both highly organized and less resistant to radioactivity. A comparative analysis of the species' resistance to radioactivity and their capacity to incorporate different amounts of various radioisotopes in respective organs would probably also explain the impoverishment of aquatic biocenoses, and the diminished numbers and complete disappearance of certain species of fishes in natural reservoirs polluted with the drainage from experimental reactors /27/.
The intensity and frequency of hereditary changes induced by ionizing radiations have been studied by radiation genetics using extensive data. Radioecology is closely bound with population genetics, which is concerned with studies of the statistical patterns that govern hereditary transforma tions in large populations of different species. Transformations, induced by ionizing radiations /55/ weaken the species. The percentage of indi viduals in the local population (of any given species) with low viability, or none at all, increases; hence the population is reduced as a result of unfavorable environmental factors and lowered fecundity.
After a certain number of generations (especially under continuous ex posure to ionizing radiations) such a population will probably disappear, and individuals of the species will no longer be found j.ri areas contaminated by radioisotopes with long half-lives.
Thus, in the case of contamination of natural habitats by radioactive isotopes, radioecology could, in principle, predict the trend of future changes in the evolving interrelationships, and its task should include the regulation and prevention of undesirable changes.