Australian frogs are on the brink of extinction, and four species likely already lost, scientists say

2021-08-20

Australian frogs are being pushed towards the precipice of extinction by disease, climate change and invasive animals.

Key points:

• Eight Australian frog species are at “high risk” of becoming extinct in the next 20 years

• Chytrid fungal disease, climate change, and invasive species are behind the decline

• Creating safe refuges for frogs in the wild and captive breeding are key to averting more species loss

A team of 29 scientists from across Australia has warned that a number of frog species will go extinct in the next two decades if no action is taken.

Eight species are at “high risk” of extinction in the next 20 years, but four of those are likely to be already lost, according to the research published in the journal Pacific Conservation Biology today.

The study ranked the extinction probability for Australia’s threatened frogs to identify the species most in need of intervention, according to study author Graeme Gillespie of the Northern Territory Department of Environment, Parks and Water Security.

Dr Gillespie said frogs would soon follow the path of Australian reptiles, mammals, birds and plants that have already become extinct, adding to the country’s already dire biodiversity record.

“The evidence is there, the patterns are there, this study tells us we’re about to lose more,” he said.

The study’s lead author, Hayley Geyle of the NESP Threatened Species Recovery Hub, said urgent action was needed to protect these unique species.

“Current resourcing and management is just not cutting it in terms of preventing declines,” she said.

Disease causing extinction

The amphibian disease chytridiomycosis (or chrytrid), caused by the fungal skin pathogen Batrachochytrium dendrobatidis, has likely already driven four species extinct, according to Dr Gillespie.

Species likely extinct:

• Northern tinker frog, Taudactylus rheophilus, QLD.

• Northern gastric-brooding frog, Rheobatrachus vitellinus, QLD.

• Mountain mist frog, Litoria nyakalensis, QLD.

• Yellow-spotted tree frog, Litoria castanea, NSW/ACT.

“This disease has been responsible for the extinction of hundreds of species of frogs around the world, including in Australia, and the decline of many others,” he said.

“For the species which we believe are extinct, chytrid is probably the exclusive factor.”

But for many of our other critically endangered frogs, the threats of climate change, invasive species and habitat loss are also at play.

“What these things do is they reduce the overall resilience of the species to cope with a new threat,” Dr Gillespie said.

“If a frog occurs on one mountaintop like Kosciuszko, there is a chance for the entire species to be knocked out by one event like a fire.”

Climate change may be impacting lowland frog species too, according to Ed Meyer of the Queensland Frog Society, who has been involved in monitoring frogs in groundwater dependent wetlands.

“We think the rainfall deficits we’ve had in south-east Queensland have resulted in the local extirpation of populations of some of those species,” Dr Meyer said.

Dr Meyer said the study clarified just how dire the situation was for a large number of Australian frogs.

“We risk losing additional species in a very short time space, perhaps shorter than people realise,” said Dr Meyer, who was not one of the authors.

Disparity in frog conservation investment

After the Black Summer bush fires tore across Mt Kosciuszko in 2019/20, a rescue mission was launched to see how the critically endangered southern corroboree frogs had fared in their protected enclosures in the alpine bogs.

Several enclosures were destroyed and close to two-thirds of the frogs died, but scientists hope frog numbers could bounce back thanks to an extensive captive breeding program for the species.

But there isn’t adequate data on the ecology or populations of many other frog species at risk of extinction, let alone captive management programs.

“There’s definitely a big disparity in those frogs on the list in terms of the amount of investment that’s gone into securing their future,” Ms Geyle said.

“So one of the key actions would be to put in place more research and monitoring of the populations.”

Dr Meyer agreed that because some species receive more attention than others, we don’t have a good understanding of their vulnerability to threats.

“We perhaps don’t appreciate just how how much of a knife edge they’re on, until they fall over the other side,” he said.

Captive breeding challenges

Even for species that do have captive management programs underway, their release into the wild is not immediately guaranteed.

The Kroombit tinker frog that lives in rainforest streams in central Queensland is the species most likely to go extinct by 2040 according to the new study, after the four species already believed to have disappeared.

Dr Meyer has been studying the frog since the mid 1990s and has witnessed its decline in the wild.

He said his team faced political and funding challenges when they set up a captive breeding program for the Kroombit tinker frog 13 years ago, but they’ve now successfully bred the frog in captivity.

“We’re currently putting together a formal captive release plan strategy to make sure that we get [the release] right,” he said.

“We’re going to give it a red-hot go and hopefully we can buy the species some time and maybe give it a brighter future.”

Captive breeding programs are expensive, time-consuming and the last resort, said Dr Gillespie, but there are other things that can be done.

“We can build resilience in these species by addressing management issues that we do have some control over,” he said.

“In some cases, it’s just a matter of putting in appropriate fencing or undertaking appropriate pest management.

“We know how to control pigs. It’s not technologically very difficult.”

Relocating frogs to safer habitats or even wild refuges is another potential solution.

Dr Gillespie also thinks crisis funding for threatened species could be put to better use.

“If the resources that were being thrown around in response to those [2019] fires had been spread out uniformly over the previous 10 years, we would’ve had a better outcome,” he said.

“We would have been more informed about the likely impacts, and there would have been more resilience in the system.

“But a big bag of money gets thrown at it, it gets spent in a short period of time, and then it goes back down to being inadequate until the next crisis.”

A spokesperson for the federal environment department said they welcomed the research findings, and that the government was committed to recovering threatened species.

They said government programs were “increasingly incorporating monitoring for on-ground projects to better assess the outcomes of Australian government investment and to inform future actions”.

abc.net.au, 20 August 2021
; https://www.abc.net.au