 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 amphibian decline is recognized as a modern-day global mass extinction .













































