In a separate experiment, Kiesecker confirmed the field observations by rearing toad eggs at various depths within an enclosure placed in one of the ponds. Kiesecker now believes that climatic change plays a much larger role in the toad die-offs than does ozone depletion. I was really glad we'd spent all those years baby-sitting ultraviolet experiments in the mountains. Otherwise, I don't think we'd have seen the connection. Kiesecker's conclusions are hotly debated among scientists.
Many researchers doubt that the effects of UV radiation in Oregon are seen elsewhere.
There is also disagreement over whether Saprolegnia is an active pathogen or merely a mold that grows on eggs that have died of a different cause. David Green of McGill University in Montreal, who has studied toads for years, said Kiesecker's water-depth experiment lends credence to the field data. But the long string of circumstantial evidence behind the interpretation needs closer examination, he said. But it is so tenuous that you have to wonder if what's actually happening has to be this complicated. And it's all based on correlations.