Stuart et al., 2004. Status and trends of amphibian declines and extinctions worldwide. Science, 306 (5702): 1783 - 1786. - [
public link -
NUS link]
"Scientists first became concerned about wide-spread amphibian population declines when they met in 1989 at the First World Congress of Herpetology. Historical data indicate that declines began as early as the 1970s in the western United States, Puerto Rico, and northeastern Australia. Subsequent reports revealed the severity of the declines."
"The lack of a comprehensive picture of the extent and severity of amphibian declines prompted us to conduct the IUCN–The World Conservation Union Global Amphibian Assessment (GAA) to gather data on the distribution, abundance, population trends, habitat associations, and threats for all ... described species of amphibians".
"The lack of conservation remedies for these poorly understood declines means that hundreds of amphibian species now face extinction."
The Global Amphibian Assessment is the first-ever comprehensive assessment of the conservation status of the world's 5,918 known species of frogs, toads, salamanders, and caecilians.
They found that nearly one-third (32%) of the world’s amphibian species are threatened, representing 1,856 species.
To find out more about Amphibians WorldWide, see Amphibiaweb - which says, by the way, that "the current number of amphibian species: 6,234 (Oct 31, 2007)".