Amphibians include about 7000 species of frogs, toads, salamanders and caecilians. They are one of the most highly threatened groups of animals. Almost one-third of all amphibian species are listed as globally threatened and almost half are experiencing population declines. This means that amphibians more highly threatened and are declining faster than either birds or mammals. Over 30 amphibian species are thought to have become extinct in recent decades. Extinct frogs include the iconic Australian Gastric Brooding Frog, which famously raised its eggs in its stomach to protect them from predators.
Dramatic declines in amphibian populations were first noticed by scientists around the world in the 1980s. Surprisingly, many of these declines occurred in protected areas and pristine habitats, far from obvious human impacts.
The causes of amphibian declines are varied, complex and are poorly-understood. Some reasons for their decline include habitat loss and modification, disease, exploitation for food, medicine and the pet trade, pollution, introduced species, ultraviolet-B radiation (UV-B) and climate change.
One of the biggest reasons that amphibian population are declining is the disease chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis. This disease was discovered only in the late 1990s and is thought to be responsible for mass deaths, population declines and extinctions in Australia, New Zealand, Central and North America, Europe and Africa. Controlling the global movement of live amphibians as pets is an important way to protect amphibians from this and other diseases.
Why should we care if amphibian populations decline or disappear altogether? Amphibians are an essential part of healthy ecosystems. They are an important consumer of invertebrates and a key source of food for many other animals. In places where amphibian populations have dramatically declined, the impact is clear: snakes are starving to death and disappearing from areas, and streams are becoming choked with algae without tadpoles to feed on it.