Rare Booroolong frogs, native to the NSW Northern Tablelands, are being supported to build up numbers in captivity after a severe drought pushed the species to the brink.

The 58 frogs are an "insurance colony", Michael McFadden, unit supervisor of the Herpetofauna Department at Taronga Zoo said.

The frogs had been affected by drying streams in recent droughts, sediment build-up in waterways, and chytrid fungus, Mr McFadden said.

The widespread fungus causes a highly infectious disease that can kill amphibians quickly.

"In the recent 2019 drought, the Boorolong frog's habitat was drying up," he said, adding many failed to breed in that period.

The alarm was raised that the amphibians were disappearing "at a rapid rate".

Work was quickly undertaken to salvage the species, with a survey of the habitat finding 60 Booroolong frogs, with help from Taronga Zoo, the Australian Museum and the NSW government's Saving Our Species program.

"That was almost all we could find of the species at the time," he said.

The frogs have been moved into a $178,000 dedicated breeding facility, funded by the Saving Our Species program.

"The extended drought we had in northern NSW certainly had a big impact on this species," he said.

"It's evident they probably disappeared from some of the local streams they were found in."

The most benefit for the species would come from captive breeding before the species could be reintroduced to the wild, he said.

Australian amphibians numbers were in decline due to threats from droughts, bushfires and the "devastating" chytrid fungus, Environment Minister James Griffin said.

"That's why this World Wetlands Day, we're celebrating the success of the Booroolong frog captive breeding program, and we're hoping it'll ultimately help revive their wetland habitat."

"We know that habitat protection and conservation is critical for securing the future of this important native species."

Australian Associated Press