It’s more than 50 years since an Australian mammal became extinct, so my generation has been spared the shame of the loss of the thylacine and any of the other 20 unique creatures to have vanished from Australia since European settlement. Many of us believed we’d won the war to preserve Australia’s biodiversity – that a more caring attitude towards our wildlife, more national parks and better management practices by rural Australians had brought the extinctions to an end. But now we know better, for the extinctions are about to resume, and there is no doubt that without urgent action they will build into the biggest extinction wave of all.

The destruction of Australia’s unique biodiversity began almost as soon as Europeans arrived. The last time anyone saw Lord Howe Island’s white gallinule (a waterbird) was in 1788, when the First Fleeters pillaged the island for food. Western Australia’s big-eared hopping-mouse was last seen in 1843; the white-footed rabbit-rat (which was very cute), in 1845; and Gould’s mouse, 1857. All were once common: convicts recorded that the rabbit-rat raided their precious grain stores in Sydney in 1789, and the naturalist John Gould wrote of seeing Gould’s mouse (which he named in honour of his wife) nesting by a homestead gate in the Hunter Valley in the 1840s.

The loss of these creatures constitutes the first wave of Australian extinction. The cause of their demise is difficult to determine, but the changed use of fire, the introduction of livestock and the spread of cats all probably played a role. Whatever the case, it’s likely that our ancestors bid them good riddance, for so little did they think of them that all that remains of these animals today is the odd desiccated museum skin or drawing.

The second wave of extinction began with the introduction of foxes and rabbits, in the late nineteenth century. It rolled on right up to 1956, and by the time it was finished 15 unique mammal species had gone forever, including almost every mammal in the drier country bigger than a rat and smaller than a kangaroo. Indeed, all of the land south of the tropics was devastated to the point that most Australians my age have never seen a wallaby or a bandicoot outside a zoo. Yet these creatures were once so common that bounties were paid on millions of their scalps, and they gave rise to such distinctively Australian sayings as ‘on the wallaby track’ and ‘lousy as a bandicoot’. I was born in the same year as the last extinction of the second wave – that of the crescent nailtail wallaby. The skin of the last wallaby to be preserved resides in the Australian Museum, Sydney, where I once worked. It was the most gorgeous creature, with fur so plush it would shame a chinchilla.

Most Australians of my parents’ and grandparents’ generations hardly seemed to care about this second wave of extinctions. I once asked an older colleague why Australian scientists didn’t act to save such beautiful and unique creatures – which would not have been hard to do, as many similar species breed prolifically in captivity. He replied that in the age of Watson and Crick and nuclear power, no Australian researcher worth his salt wanted to stay in the country. Cambridge and Harvard were where the real scientific action was. And so the extinctions rolled on unchallenged, depriving all Australians forever of the joy of knowing a continent alive with its marsupial heritage.

With the third wave of extinction swelling, a generation of Australian scientists is at last mounting a rearguard action to preserve our unique biodiversity. But so miserable is the funding, and so immense the task, that species are slipping away before their eyes, even in the best-protected wildernesses. Mount Lewis, in north-east Queensland, is a jewel in the crown of Australia’s World Heritage wet tropics. It’s a place seemingly untouched by the modern world, full of ancient rainforest life, much of it found nowhere else on Earth. If you had taken a night-time walk through that forest a few years ago, you might have seen a distinctive white possum with eyes like coals peering down at you from the treetops. Known as the lemuroid possum, they are easy to spot, for they are noisy and constantly leaping from one tree to another. Even now you can see a dwindling number of lemuroid possums further south, on the Atherton Tablelands, but the Mount Lewis animals are genetically distinct, about one in five being albino.

Scientists have been studying the Mount Lewis ringtails for decades. In the 1980s the possums were so abundant that more than one was seen per hour of spotlighting. In the ’90s they were less common; but then suddenly, in 2005, scientists stopped seeing them. For three years there was not a single sighting until, in early 2009, a tiny remnant population was located. What could possibly have destroyed a creature living in such pristine habitat?

The fate of the lemuroid possum had been predicted in 2003, when a group of researchers used computer models to assess the impact of increasing temperature on rainforest animals. Many species, they found, could not tolerate even a small rise in temperature. The lemuroid ringtail was one of the most vulnerable, being unable to tolerate temperatures above 28° Celsius for more than a few hours. The scientists predicted that extinctions would begin to occur when the average temperature rose by around 2°, and would pick up pace when the temperature rose by 3.6°. Because such warming was not expected until 2050 or later, scientists believed we had decades to deal with the problem. No one, however, anticipated the effect of extreme weather.

Researchers have now shown that short-lived heatwaves are killing Australia’s animals. After each heatwave fewer possums were spotted, until an exceptionally hot day in 2005 brought the creature to the brink of extinction. With more heatwaves inevitable, the white lemuroid possum will almost certainly become extinct in the wild in the next few years. And this is a tragedy, for the lemuroid ringtail is a truly ancient Australian, with a fossil record going back more than 5 million years.

The white lemuroid possum is just the photogenic tip of a huge extinction iceberg. A tiny bat, the Christmas Island pipistrelle, will probably beat the possum to extinction. A few years ago it was abundant on the island, but by early 2009 just 20 remained. Such is its rate of decline that it will be extinct by the end of this year, unless the most determined effort is made. The mountain pygmy-possum is an ancient Australian with a fossil record going back around 20 million years, and it’s not far behind the bat in the extinction stakes. Restricted to Australia’s alpine country, its population has recently plunged by more than 90%, prompting its 2008 listing by the International Union for the Conservation of Nature as “critically endangered”. Ominously, no one has assessed its population since the catastrophic Victorian bushfires. Computer modelling, though, indicates that just a 1° rise in the average temperature will drive it to extinction; and, as temperatures rise further, most of Australia’s unique alpine habitat is likely to follow.

Behind these species teetering on the brink are whole ecosystems in peril, for the extinction wave that devastated southern Australia a century ago is now sweeping the north. Around half of northern Australia’s medium-sized mammals (such as bandicoots and wallabies) have declined in population by 90%, and most of the remainder are so poorly studied that we have no idea how endangered they are. Three quarters of the region’s native rodents have declined catastrophically, and even many of the smaller, more resilient species are in seemingly terminal decline, having been found in many surveys to have diminished in abundance by 95%. All of this has happened over the past ten to 30 years, as national parks have grown, along with environmental awareness. While the causes remain uncertain, altered fire regimes, cats and a changing climate are likely all playing a part.

The rusted-on climate sceptics and those who don’t give a stuff about their natural heritage argue that it’s impossible to know whether a species is extinct, or what caused a species’ extinction. If that argument fails they’ll say that it doesn’t matter anyway, because species are always becoming extinct. Such deceptions are a gross insult to scientists and, indeed, all Australians. Of course there’ll always be arguments about the cause of extinctions, and there’s a slim hope that some remnant populations have survived. But the trend is clear. We are losing our precious native animals, and it’s happening on our watch. And it really matters. The extinctions we’re seeing are stripping our heritage from us at a rate thousands of times faster than occurred in pre-European times, and that is leading to ever more fragile and less-well-functioning ecosystems.

The success of groups such as the Australian Wildlife Conservancy (a not-for-profit organisation of which I am a director), funded by donations from ordinary Australians, shows just how out of step with public sentiment are the sceptics. Without the work of the AWC, species such as the woylie and the Shark Bay mouse would be on the verge of extinction today, and the group’s work in northern Australia is turning the extinction tide wherever it manages land. But without a concerted national effort, more extinctions are inevitable.

If the Australian government was at all serious about climate-change mitigation, it would be pumping millions of dollars into surveys and captive-breeding programs for the most critically endangered species. Instead, we see business as usual: mouthed concern, but no meaningful action to deal with the consequences of our coal burning. Without doubt, climate change is only one factor at work, but no one can gainsay that it’s a deadly serious one, with computer models indicating that we face losing three out of five species on Earth to global warming if the worst-case scenario eventuates.

What should we think of an Australia that pours $42 billion into a brown economic-stimulus package to save a faltering economy, yet stands by with hands in pockets as one species after another slides towards extinction? Any thinking person would look on such short-sightedness with disgust. We’ll have our say again soon, most likely in 2010, and if enough Australians make themselves heard, one day we just might be led by a government that really cares about this country – animals and all – in the way it deserves.