 Although scientists observed reduction in populations of several European amphibian species since the 1950s , awareness of the decline of amphibian populations and its classification as a modern @-@ day global mass extinction only dates from the 1980s . By 1993 , more than 500 species of frogs and salamanders present on all five continents were in decline . Today , the phenomenon of declining amphibian populations affects thousands of species in all types of ecosystems and is thus recognized as one of the most severe examples of the Holocene extinction , with severe implications for global biodiversity . 
