The author of this letter concludes that a wordwide decline in the number of amphibians is the indicateion,or result, of global air and water pollution.To support this assertion the author first notes a decline in amphibians in Yosemite Park between 1915 and 1992, and acknowledges that trout, which eat amphibian eggs, were intruduced in there in 1925. But, the author then claims that the intruduction of trout cannot be the reason for the decline in Yosemite Park because the introducion of trout in Yosemite does not explain the worldwide decline. I find this argument logically unconvincing in three critical respects. First, the author falis to provide any envidence to refute the strong inference that the decline in the number of amphibians was indeed caused by trout. Because the author dose not provide no affirmative evidence that pollution-- or some other phenomenon-- was instead the reason for the decline, the author's board assertion that wordwide decline in amphibians indicates global pollution is entirely unconvicing. Seconde, even if I were concede that the intruduction of trout was not the couse of Yosemite's amphibian decline, the author provide the decline was caused by pollution-- rather than some other phenomenon. Perhaps some other environmental factor was instead the cause. Without ruling out all orther possible explanations the author cannot covince me that pollution is the cause of the worldwide amphibian decline-- or even the decline in Yosemite alone. Thirdly, even if I were concede that pollution caused Yosemite's amphibians decline, this single sample is insufficient to draw any general conclusion about the reason for wordwide amphibian decline. It is entirely possible that the cause-and-effect relationships in Yosemite are not typical of the world in general. Without addittional samples from diverse geographic locations, I cannot accept the author's sweeping generalization about the decline of amphibians and global pollution. In sum, the scant evidence the author cites proves nothing about the reason for the general decline of amphibians wordwide; in fact, this evidence only serves to refute the author's own argument. To strengthen the argument the author should examine all changes occuring in Yosemit between 1915 and 1992, nad shouw that air and water pollution have at least contributed to the park's amphibian decline. In any event, the author must provide data about amphibian population changes and pollution at diverse geographical locations; and this data must show a strong inverse correlation between levels of air and water pollution and amphibian population worldwide.