Decline in Amphibian Populations - Background

Background

In the past three decades, declines in populations of amphibians (the class of organisms that includes frogs, toads, salamanders, newts, and caecilians) have occurred worldwide. In 2004, the results were published of the first worldwide assessment of amphibian populations, the Global Amphibian Assessment. This found that 32% of species were globally threatened, at least 43% were experiencing some form of population decrease, and that between 9 and 122 species have become extinct since 1980. As of 2010, the IUCN Red List, which incorporates the Global Amphibian Assessment and subsequent updates, lists 486 amphibian species as "Critically Endangered".

Habitat loss, disease and climate change are thought to be responsible for the drastic decline in populations in recent years. Declines have been particularly intense in the western United States, Central America, South America, eastern Australia and Fiji (although cases of amphibian extinctions have appeared worldwide). While human activities are causing a loss of much of the world’s biodiversity, amphibians appear to be suffering much greater effects than other classes of organism. Because amphibians generally have a two-staged life cycle consisting of both aquatic (larvae) and terrestrial (adult) phases, they are sensitive to both terrestrial and aquatic environmental effects. Because their skins are highly permeable, they may be more susceptible to toxins in the environment than other organisms such as birds or mammals. Many scientists believe that amphibians serve as "canaries in a coal mine," and that declines in amphibian populations and species indicate that other groups of animals and plants will soon be at risk.

Declines in amphibian populations were first widely recognized in the late 1980s, when a large gathering of herpetologists reported noticing declines in populations in amphibians across the globe. Among these species, the Golden toad (Bufo periglenes) endemic to Monteverde, Costa Rica, featured prominently. It was the subject of scientific research until populations suddenly crashed in 1987 and it had disappeared completely by 1989. Other species at Monteverde, including the Monteverde Harlequin Frog (Atelopus varius), also disappeared at the same time. Because these species were located in the pristine Monteverde Cloud Forest Reserve, and these extinctions could not be related to local human activities, they raised particular concern among biologists.