Frogs, toads, and other amphibians throughout the world are disappearing at an alarming rate, according to the biggest statistical study of the topic ever completed, published in today’s issue of the journal Nature. Researchers found that the overall numbers of amphibians dropped 15 percent a year from 1960 to 1966, and continued to decline about 2 percent a year through 1997. The data indicate that the amphibian decline began well before scientists first sounded the alarm about the issue in the 1980s. Scientists aren’t sure about the cause, but they suspect a combination of factors, including the widespread use of pesticides and fertilizers, loss of wetlands to development, the introduction of exotic predators, and increased ultraviolet light as a result of a thinning ozone layer.