The International Union for the Conservation of Nature, Conservation International and other groups said they plan a series of emergency actions and long-term research.
It will include describing at least 1,000 new species, preventing future habitat loss and reducing trade in amphibians for food and pets.
The groups are looking to governments, private institutions and individual donors for money.
“The frogs are trying to tell us something,” said Andrew Dobson, a professor at New Jersey’s Princeton University who studies infectious diseases in the wild.
“We’re making the world a sicker place and, mercifully, the frogs have picked up on it before us humans.”
Almost a third of known species of frogs, toads and other amphibians are considered “globally threatened” by the IUCN, which is based in Gland, Switzerland.
By comparison, 23 per cent of mammal species and 12 per cent of bird species are threatened.
Declines and disappearance of amphibian species are occurring mostly in North and South America, Puerto Rico and Australia.
The chief causes are a fungal disease that tends to occur at higher elevations and by streams, habitat loss and degradation, climate change, chemical pollution, nonnative species and over harvesting of amphibians for food and pets.
“The fungus is the cause of a lot of the massive die-offs we’re seeing in recent years,” said Claude Gascon, a senior vice president at Conservation International.
Scientists have discovered 5,743 species of amphibians so far, but believe about 10,000 exist.
Those include frogs, toads, salamanders and caecilians, snakelike creatures that live mostly underground.
At least 43 per cent of species are declining in population size, including 1,856 that might soon become extinct, according to a team of 500 scientists in 60 countries.
In the past 35 years, they believe, 122 species already might have disappeared.