Bad news for Australian mammal extinction
AUSTRALIAN LAND MAMMALS Have been declining at striking rates in the past decades, according to the key finding of a recent report by a team of researchers from Charles Darwin University, Northern Territory.
Since Europeans settled in Australia in 1788, Australia’s terrestrial animals have been steadily wiped out says conservation biologist John Woinarski, lead author of the study.
“Mammal species started becoming extinct within about 60 years of that settlement, and extinctions at the rate of one to two species per decade have continued unabated since, such that a total of 30 of Australia’s land mammals are now extinct – more than 10 per cent of the original endemic land mammal fauna” he says.
The review of 3000 Australian mammal studies, published in the Proceedings of the National Academy of Sciences, represents the first comprehensive analysis of the true extinction crisis affecting Australian land mammals, says Dr Robert Davis, a conservation biologist from Edith Cowan University, in Joondalup, Western Australia.
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“Fauna disappearing before our eyes”
Each of the authors of this new report have been studying mammals for over 30 years, and has witnessed much decline over that period, says John. In the Top End of the Northern Territory the researchers started to notice a troubling trend.
“Initially, our survey traps were full of mammals, but over the course of one to two decades of research there, trap rates declined precipitously and we were unable to encounter some species that were previously common,” he says.
As John and colleagues expanded their sampling, they noticed their observation of declining mammals was not an isolated problem. “As our sampling got wider and wider and our sampling base more considerable, it became evident that this was not an isolated problem, nor a natural fluctuation, but rather fauna disappearing before our eyes,” he adds.
Extinction causes unique to Australia
The study identifies several extinction drivers that are unique to Australia, says Robert. “The impact of feral animals, particularly introduced foxes and cats are highlighted, along with inappropriate fire regimes, as the primary contributors of decline,” he says. “This sets us apart from much of the world where hunting and habitat loss are the primary causes of extinction”.
The impact of red foxes and feral cats are particularly important, notes Dr Mike Letnic, an ecologist from the University of New South Wales, because we have little means to deal with their impact.
“Sadly, however, there is only limited capacity to manage the threat posed by foxes and almost no answer to the threat posed by cats. We desperately need to put in place strategies to combat the impacts that foxes and cats are having on Australia’s mammals,” he says.
John also points to the impact caused by changes in fire management. Prior to European settlement “Aboriginal landholders managed fire skilfully, typically crafting their lands through many fine-scale fires,” he says. Now, fire is “less skilfully applied” says John, and they tend to be larger and more destructive.
On top of these problems, the authors say that Australian mammals are also affected by factors such as disease, habitat degradation, and even poisoning, a consequence of the introduced cane toad.
Australian animals extinct before we’ve found them
The decline affecting Australian mammals represents the highest mammal extinction rate reported anywhere in the world over this short time frame, the authors say, and their estimate are higher than previously reported.
So far, about 10 per cent of Australian endemic mammal species have disappeared since European settlement. Furthermore, many other species are in jeopardy, says John.
“Fifty-six Australian land mammals are now threatened, indicating that this extremely high rate of biodiversity loss is likely to continue unless substantial changes are made,” he says.
Until now, these declines have remained largely unremarked as many of species lost are small, elusive nocturnal species. “Few Australians know of these species, let alone have seen them, so their loss has been largely unappreciated by the community,” adds John. In addition, “much of the loss has occurred in largely natural areas remote from human population or obvious disturbance”, says John.
Hope for saving Australian mammals
Is there hope for Australian mammals? John says their fate can be improved, but it will be a “formidable challenge”. Future efforts need to quantify the extent of species loss, and estimate the odds for the future, he says.
“It comes down to a fundamental reflection on what it is that we value, and how much we should appreciate the distinctiveness of Australia’s environments and wildlife. If we care enough about our natural heritage, we will better make the effort to maintain it,” says John.
A promising sign, notices John, is the recent pledge by the Australian Minister for the Environment to improve the conservation status of 20 threatened Australian mammal species by 2020, and the appointment of Australia’s first Threatened Species Commissioner.
On other fronts, John says that Australia’s offshore islands may serve as havens for threatened species. “Many mammal species that are imperilled on mainland Australia can be translocated to islands – operating as arks – or to small mainland areas in which predators are excluded, by special fencing, or intensively controlled,” he says.
Other approaches that may help include broad scale baiting, which has shown some success for controlling introduced foxes, and will soon be tested against feral cats. Also, restoration and protection of some native fauna, such as dingo populations that were recently found to protect the dusky hopping mouse, may prove useful against introduced predators, John says.
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