Black Saturday frog study finds extreme bushfires threaten amphibians' future
28 June 2017
published by www.abc.net.au
Australia - The risk of an increasing number and intensity of bushfires
should be added to the list of long-term threats facing Australia's frog
species, according to an ecologist.
The results of a seven-year study suggest that, as bushfires became more frequent due to a changing climate, there is a greater chance of some frog species becoming extinct.
University of the Sunshine Coast lecturer in animal ecology Dominque Potvin modified her research after the Black Saturday bushfires destroyed the local frog population to investigate how severe bushfires affected their survival.
"When the fires went through it was devastating — not just for the people and the land but also for our research," she said.
"But we took it as an opportunity to go out afterwards and try to see how the frogs in the area were doing.
"What we discovered was disheartening and should act as a warning call when developing future management and conservation strategies for the survival of our fauna in all fire-prone areas.
"While one species, the brown tree frog, seemed to recover quite well by that point … the Victorian tree frog, still had not recovered its original genetic variability even five years after that fire had ripped through."
Wiping out genetic variability
The Black Saturday bushfires burned across Victoria in February 2009, killing 173 people and destroying more than 3,500 structures.
In total, it burnt 4,451 square kilometres of land, with 1096 square kilometres of bushland, private forest and plantation timber destroyed.
The findings of the frog study, published in the Journal of Applied Ecology, centred around the Kinglake area.
"For two years leading up to Black Saturday, we were doing research into the ecological and genetic diversity of two common species," Dr Potvin said.
Having the baseline data was critical to the research as the team could then measure the recovery of the frog species over the following five years.
Sound recordings of frog calls in the early stages of research gave the researchers hope, but mostly turned out to be male bravado.
"We went out with a microphone and recorded the sounds of the frogs and we actually thought that the populations were doing quite well, they were resilient, they had made it through and we were really excited," Dr Potvin said.
"They're in really high competition and the males are calling because they each want a female.
"It could be if there is a very limited pool of females, for instance if they all got wiped out by a fire, the competition for those females is even more intense."
The research team also used genetic testing on the frog population, which is where they found that both species were more inbred after the fires, putting at risk their ability to adapt to future change.
"[Genetic variability] is just one of those things that is really important for long-term persistence, survival under multiple scenarios, and for reproduction into the future," Dr Potvin said.
"If you only have a limited pool of genes, if one disease comes through and nobody has the gene to be immune to that disease then they're all wiped out.
"When a species faces a new environment, changes in its environment or a new disease comes through, it relies on genetic variability to deal with that."
A climate of increasing bushfire risk
Climate models predict that large bushfire events in Australia will become more common.
In 2016, the study Natural hazards in Australia: extreme bushfire found that a major factor contributing to extreme fires was atmospheric stability.
Unstable atmospheric conditions mean fire plumes can develop higher than they normally would, which leads to more severe fires at ground level.
Unfortunately, climate change means Australia will experience more days of atmospheric instability, and Dr Potvin said we should be paying attention to how frogs adapted.
"Frogs are a really good indicator species of troubles that might occur in an environment due to changes such as climate change," Dr Potvin said.
"Nobody had really been able to do what we had done before, to look at a snapshot before a big intense fire.
"So to find that these patterns might emerge, where you might get a lot of inbreeding, was something that had been considered in the past but not actually tested."
A brown tree from sits atop a large blade of green grass.
The implications of the study Dr Potvin said could be applied to other species living in areas that are subject to bushfires, and should play a larger role in discussions around conservation.
"We used frogs because we had the data, but it's likely indicative of other species that have similar patterns of movement, require similar habitats, and could be similarly susceptible to fire," she said.
"[But] it's not just about frogs, it's about a whole lot of other species that live in our natural environment that keep things balanced.
"So when we're looking at how to keep our environment healthy long term, we really need to consider the different factors that might play into that health."