There is some controversy about the effects of moderately increased radiation levels on ecosystem health. Following the Chernobyl disaster in 1986, and the resulting human evacuation of the area,animal populations in the area increased both in size and in diversity.Some evidence has suggested, however, that at least for some species such as barn swallows the area has become a population sink, not only unable to sustain a healthy population but drawing in creatures from adjoining areas and depleting those other populations. Investigate and evaluate the arguments and evidence on the two sides of this controversy and discuss.