The causes of these historical extinctions are difficult to determine. Amphibians evolved around 350 million years ago during the Devonian period and have survived 3 mass extinction events. The three main groups of amphibians are frogs, salamanders, and caecilians. Declining amphibian populations have also been attributed to regional phenomena like changes in climate, introduction of non-native competitive species, or exposure to pathogens. Many herpetologists believe that a combination of stresses is being placed on amphibian populations, and that the combination of stresses puts some species more at risk than others.
Amphibians have many unique or unusual developmental characteristics.
There is a need for a better understanding of habitat suitability and the stressors that affect amphibian populations over a wide range of ecoregions. References Alford, R.A. and Richards, S.J., 1999. A problem in applied ecology. Alvarez, L.W., Alvarez, W., Asaro, F., and Michel, H.V., 1980. Extraterrestrial cause for the Cretaceous-Tertiary extinction.