species, the predicted population size decreased and the prob-
ability of extinction increased as fire frequency increased from
an average of one fire every 100 years to one every 10 years.
This means that as severe fires, like those of Black Saturday,
become more frequent there is a greater likelihood of frog popu-
lations becoming extinct. However, we did find that these
effects were substantially reduced if the rate of migration between
populations was sufficiently high.
Under all our modelling scenarios, the conservation-listed
growling grass frog had a higher risk of extinction than the
other frogs. The results from this predictive modelling indicate
that species with an initially lower genetic diversity and/or
isolated populations of frogs with low rates of migration are
more vulnerable to extinction under the increasing fire frequen-
cies expected in south-eastern Australia due to climate change.
While natural bushfires are considered an ecologically impor-
tant part of the Australian landscape, it is predicted that current
and future climate changes will have unprecedented impacts
on the frequency and severity of fires in south-eastern Australia.
However, it is difficult to predict how changing fire regimes
might impact populations and species –even those thought to
have evolved in areas that benefit overall from natural fire over
the long-term. In the context of global change, it is important
to consider how seemingly distinct human activities, such as
changing climate, landscape modification and fragmentation,
interact when impacting natural systems. Understanding how
predicted changes might contribute to a species’ likelihood of
disappearance or persistence is a vital part of making informed
decisions about management and conservation.Previous studies have shown an intricate relationship between
climate change, habitat loss and disease in the extinction risk
of frogs. Our study on the Victorian frogs found evidence of an
additional cause of extinction risk for frogs with anthropogenic
climate change. The additional pressures of increasing bush-
fire frequency could have a profound impact on the persistence
of many small vertebrates. While it is true that many small
vertebrates living in fire-prone areas may benefit, or simply
show higher genetic diversity, from infrequent fire regimes,
increasing fire incidence is likely to be detrimental to even well-
adapted species. Our results support the disturbing suggestion
that, at least in some environments, extinctions may result from
climate-mediated causes, such as more frequent fires, long before
the physiological inability to adapt to high temperatures becomes
an issue.
Although these results portray a gloomy future for Victo-
rian frogs with a multitude of compounding extinction risks,
it does provide a warning call that some factors are particu-
larly important in the management of the long-term prospects
of our fauna. In particular, maintaining connectivity between
populations and minimising fragmentation seem to be reoc-
curring themes when assessing the ability of frogs to recover
from the impacts of ecological disturbance. We hope that our
study, and others that provide strong predictive evidence of
extinction risks in our already dwindling frog species, will be
taken into account in the development of future management
and conservation strategies.
Jane Melville is Senior Curator in Herpetology at Museums Victoria. Dominique Potvin was
a project officer at Museums Victoria for this research, and is currently lecturing in animal
ecology at The University of the Sunshine Coast.40 ||MAY/JUNE 2017
Dominique Potvin searching for frogs in the Kinglake area.
D. Paul/Museums VictoriaA pond near Kinglake 4 months
after the Black Saturday fires.
B. Bray/Museums Victoria