Feral cats and red foxes, both introduced from Europe, are behind the alarming rate of extinction of a number of native mammal species in Australia, which in turn threatens the continent's biodiversity, researchers say.
In what conservationists are terming an "extinction calamity," Australia has lost 10 percent of its native animals species in the last two centuries.
A further 21 percent are threatened and 15 percent near threatened, conservationists say.
Australia's rate of land mammal loss is the highest of any country in the world, scientists at Australia's Charles Darwin University report in in the journal Proceedings of the National Academy of Sciences.
"We knew it was bad, but I think our tallies were much worse than previously thought," says John Woinarski, a conservation biologists who led the study. "The fact that we're losing such a large proportion of our species is a problem of international importance."
Europeans brought both cats and foxes to Australia in the late 1700s. Cats, kept on ships by sailors for on-board rat control, moved onshore where they found easy pickings among the continent's small "meal-sized" mammals, while foxes brought to be hunted likewise found Australia to their liking.
Seven native mammal species once common on the Australian mainland now exist in the wild only on islands foxes and cats have not yet reached, the researchers say.
In a country with a relatively small population, it might seem Australia's wildlife would be relatively secure from threats such as habitat loss, but that's turned out not to be the case, says Stuart Pimm, an expert in species extinction.
"Other than just the sheer awful news that Australia has lost so many of its species is the fact that it's done it across areas that are very, very sparsely populated," he says. "It tells us that by being careless, particularly with invasive species, that we can do an extraordinary amount of environmental harm even in places where there aren't a lot of people."
The severity of the problem has been for the most part underestimated because many species lost or at risk are small, shy and nocturnal species many Australians have never heard of, such as the northern quoll and brush-tailed rabbit-rat, Woinarski says.
With little public profile, "few Australians know of these species, let alone have seen them, so their loss has been largely unappreciated by the community," he notes.
Invasive species are a problem in many regions of the world, the researchers point out.
"There are parts of the world where invasive species have gone amok," Pimm says, "and that tells us we need to be very careful not to bring in any more to do any more harm."
