Already devastated by a fungus made worse by changing temperatures, Australia’s frogs are at risk because of water availability and lack of refuge

Australia’s frog species, already threatened by habitat destruction and disease, are being put under extra pressure by shifting rainfall and rising temperatures from climate change.

Some of Australia’s leading frog experts are worried that serious impacts could be unfolding out of sight, with one saying climate change could push certain species to extinction before they are documented by science.

Many of Australia’s frogs are found nowhere else in the world, but the continent is also at the coalface of climate impacts with extreme heat, droughts and rising temperatures.

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Frogs are known to be at a high risk from climate change because they are ectotherms, animals with a body temperature regulated by their environment.

Global populations of frogs and other amphibians have already been devastated by chytrid fungus, a disease that broke out in the 1980s and 90s. Now climate change could wreak havoc too.

Prof Michael Mahoney, of the University of Newcastle, has spent three decades studying the amphibians. “It’s the cumulative impact,” he says. “Yes there are some frogs that were greatly reduced because of the fungus. If they now face the added insult of climate change impacts, it just makes everything all that harder.”

How many refuges are there?

To make matters worse, Australia’s 2016 national plan to reduce the impacts of the fungus speculated that climate change and warmer temperatures could also increase the vulnerability of amphibians to the disease.

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Mahoney says all frogs have a different “critical thermal maximum”, a temperature above which they die, so they have to find places to hide and stay cool and moist.

“The problem then is, how many refuges are there? The effective habitat that’s available is getting smaller and smaller. Can the frogs keep pace with current climate change? We don’t quite know the answer to that.”

Mahoney says some Australian frog species live in high elevation rainforests and cool temperate areas with a thermal maximum of 29C. “Anything above that, and they die,” he says. “In the last four to five years, there have been four or five days that have gone above 32C [in those areas].”

Climate change will have a slower impact than the fungus outbreak: “It will be a much more steady process of decline. That gives us more time to look at adaptation, but it’s also frightening because people become complacent.”

Dr Jodi Rowley, a frog expert and biologist at the Australian Museum and the University of New South Wales, says there are about 240 known frog species in Australia. However, it’s estimated about 20% of all the likely frog species in Australia have not been named and described in scientific journals.

Facebook Twitter Pinterest There’s been a decline in crawling frog (pseudophryne guentheri) numbers. Photograph: B. Maryan for Western Australian Museum

She said in south-east Asia “deforestation is happening faster than we can discover species in the forest” and the same problem could be hitting frogs in Australia.

“It’s theoretically possible that same thing could happen due to climate change, even in Australia,” Rowley said. “We also don’t know how the fungus will change and interact with climate change. Because frogs are so influenced by temperature and humidity – like the fungus – in warm dry years they huddle together and transmit disease between themselves.”

Dr Laura Brannelly, a conservation biologist at the University of Melbourne, studies how frogs cope with climate change and disease. “For frogs in particular, climate change is a real threat because they rely so much on water availability, and water patterns are changing across Australia particularly in regions like the Australian Alps,” she says.

For example, the habitat of the endangered alpine tree frog, says Brannelly, has been hit by drought and reductions in snowfall. “If there’s no snowfall, it messes with their breeding cycle. I suspect a lot of declines will be happening [in alpine regions] and climate change is a contributing factor.

“One or two consecutive bad years of extreme drought could cause an entire small population to completely disappear, which is a huge worry for species on the brink.”

Tabitha Rudin, of the University of Western Australia, is researching the crawling frog that is widespread across the southwest, an area, she says, that has seen a drop of about 19% in winter rainfall since the 1970s, with further declines predicted.

“Such drying conditions pose a growing challenge for many amphibians, particularly for terrestrial-breeding species as they deposit their eggs on land rather than water and rely on consistent rainfall whilst embryos are developing.”

Crawling frogs are able to live in places with markedly different average annual rainfall, meaning even within the species some might be better adapted to drier climates than others.

Solving the problem?

Rudin is looking to see if a technique known as “assisted gene flow” could be used to help this species, and perhaps many others, by breeding to encourage tolerance for drier conditions.

She has already produced hybrid offspring in the laboratory with greater tolerance to drying conditions. “We now have to test whether this positive effect remains over multiple generations,” she says. Rowley says a major problem for frogs is that there is comparatively little data about where they are, and so tracking changes caused by climate change or disease is hard.

To tackle this, she co-founded FrogID, a citizen science project that’s trying to track frog locations by getting users to record their calls.

“People want to know what’s going on out there with frogs and they notice changes, but the data just isn’t there,” she says. “We get lots of anecdotal stories from people who say they just don’t hear them around any more.”