Without periodic fires, the forests are over ridden with growth, and the frogs' marshland homes turn into woods. A third theory blames all of the non-native fish being added to the high elevation lakes. These fish often carry diseases that native frogs are not immune to. Herbicides and pesticides have also added to the disappearance of frogs. The poisons usually end up in the lakes and streams and, since frogs have very sensitive skin, they are the first to be affected.
Some scientists think they have found another grave threat to amphibians - increasing UV radiation.
They fear UV radiation hurts the amphibian immune system and stunts their growth. UVC, the most dangerous kind, ranges in wavelength from 265 nanometers to 280 nanometers. UVC cannot be found in the Earth's lower atmosphere because the ozone layer and upper atmosphere block all of it out. UVB, the second form of ultra-violet radiation, ranges from 280 nm to 320 nm. Before the recent depletion of the ozone layer, UVB was almost completely blocked out.