The following is a letter to the editor of an environmental magazine."The decline in the numbers of amphibians worldwide clearly indicates the global pollution of water and air. Two studies of amphibians in Yosemite National Park in California confirm my

In this editorial the author asserts that the decrease in the numbers of amphibians worldwide is because of the global pollution of water and air. To support this assertion he cites two studies of amphibians in Yosemite National Park in California showing that seven species of amphibians in the park with abundant numbers of each species has declined to four species with drastically reduced numbers of each one from 1915 to 1992. He also claims that this decline can not be attributed to the introduction of trout into the park's waters since it has occurred only in Yosemite and is not a worldwide event. A close scrutiny to the evidence reveals that it lends little credence to this argument.

First, the author provides no evidence that the studies’ results are statically reliable. In order to establish a strong conclusion, the studies’ sample must be sufficient in size and representative of the overall population of amphibians worldwide. Lacking evidence of a sufficiently representative sample, the author cannot justifiably rely on the studies to draw any conclusion.

Second, the author unfairly assumes that the decline in the population of the amphibians in the park is due to the water and air contamination. There might be other reasons such as lack of medical care and dearth of healthy foods for the amphibians which lead to outbreak of diseases among the animals or to their malnutrition and consequently their high number of mortality. And without considering and ruling out these and other possible causes the author cannot substantially impute this decline to pollution.

Third, the author unreasonably concludes that trout cannot be the real reason for the Yosemite decline since it does not explain the worldwide decline. Even assuming that this decline has been experienced worldwide, different places around the world can hold distinct reasons for this decline based on the various environmental and climate features in different areas. Therefore, lacking clear opposite evidence, the trout can be the distinct reason in decrease of amphibian in the Yosemite National Park without contracting with the worldwide decline.

In sum, this conclusion is not well supported. To bolster it the author must assures me that the studies’ results reflect the cause of decline in the whole population of amphibians worldwide. To better assess the strength of this argument I need to know about other probable factors which has contributed to this decline in the park.