The Artesian Range. Credit:Nick Moir The north-west Kimberley is now the only area of mainland Australia where no mammal, and quite possibly no plant, has become extinct since white settlement. The local inhabitants are not all that makes the region remarkable. For two decades, it has become a refuge for almost all northern Australia's small mammals that have been pushed out of native habitats across the top of the continent. This lost world, largely inaccessible to humans without a helicopter, has become a modern-day Noah's Ark on a landscape with the world's worst animal extinction rate. While the region's remoteness means the populations of many species remain abundant, the broader Kimberley faces a variety of threats.

Feisty - but under threat ... a quoll encountered by the team surveying the region's rare species. Credit:Nick Moir Fire, feral cats and wild herbivores will push up to eight kinds of mammals to extinction in the next 20 years if business as usual continues. And the populations of a dozen or more species will continue their steep decline. Feral cats are by far the biggest threat to the Kimberley's biodiversity. There are at least 100,000, eating a million-plus native animals each day. They have a more direct impact than wild herbivores such as donkeys. And the impact of fire is far greater because it allows cats to hunt down small species more easily. Pressure from tourism and mining could take its toll on the region, one of the continent's 15 biodiversity hotspots, if left uncontrolled. A giant cave gecko. Credit:Nick Moir Despite Canberra's decision to place vast tracts of the west Kimberley on the National Heritage List, the scale of the problem has grown too large for governments to manage alone. It is this predicament that convinced the Australian Wildlife Conservancy, a non-profit conservation organisation, to take over the management of 150,000 hectares of wilderness in a narrow corridor of the north-west Kimberley.

Just under half the property is a mix of grassland savannahs and rolling basalt hills, bounded to the north by the mighty Charnley River. The rest of the reserve comprises the Artesian Range, from which the sanctuary takes its name; a network of sandstone ranges and dramatic escarpments carved by deep, rainforest-filled gorges. It is here that Dr Smith and his colleagues have been for the past two weeks surveying the native species. "That is a pretty rat,'' laughs Dr Sarah Legge, the AWC's national conservation and science manager. She has just arrived by helicopter to join her team and is handed a Kimberley rock at, a small native rodent endemic to the region. ''I think she's preggers,'' Legge says, examining the animal's engorged teats. Ecologist Dr Katherine Tuft weighs, measures and releases the rodent before the conversation turns to the other species the team have caught or spotted on the trip. So far they have seen many northern quolls (now regionally extinct in the Northern Territory), monjons (small rock wallabies), and a few scaly tailed possums, called wyuldas.

Around the campsite, the deep red dirt, rich with iron oxide, is pockmarked with bandicoot and rodent diggings. ''You come to a place like this and it's what the rest of northern Australia should be like,'' says Legge. While eating dinner on their first night the team had even spotted an elusive golden-backed tree rat, whose habitat has shrunk from most of northern Australia to a tiny fringe around the Artesian Range. ''We were just eating papadams and James heard a noise,'' Tuft says. ''We looked up and it was a golden-backed tree rat.'' The rodents are so rare, Legge has not seen one. She hopes they'll catch one now she has arrived. The contraction of the rat's range is symbolic of more than half of northern Australia's small mammals, whose populations over the last two decades have crashed. In the iconic World Heritage-listed Kakadu National Park, 75 per cent of small mammals have vanished in the past 15 years, despite an annual conservation investment of $18 million. To ensure they do not disappear from the Artesian Range, the AWC will conduct annual animal inventories. ''We need to know what is here, where it is and in what density,'' Legge says.

Each evening for the past two weeks the team have set close to 200 traps with mammal-style delicacies of peanut butter and oat balls laced with honey, fish oil and tuna to give them a distinct, pungent odour. The Artesian Range is rugged and unruly. There are no boarded walkways or paths to follow. To inspect the traps early the next day (sunrise is at 4:30) the scientists clamber over fractured sandstone ridges, whose size and jagged edges would pose a death trap to most people, while pushing past spiky pandanas palms and clumps of waist-high spinifex. The fine hairs on the branches of the native hibiscus are also best avoided. ''Watch those, you'll spend the rest of the day pulling them out of your hands,'' Tuft warns. The rich and abundant biodiversity of the Range has remained intact largely because of the terrain. The region's characteristic fractured rock structures, which formed when sandstone laid down some 1.8 billion years ago folded and crumpled under the pressure of several periods of tectonic plate shifting, provide considerable shelter for native animals, especially from fire. Every year about 40 per cent of the Kimberley, roughly the size of Victoria, is razed. While fire is natural here - when grass growth from the preceding wet season dries and cures it is easily ignited by lightening strikes - bushfire patterns have been adversely influenced by humans over the past few decades. This has created the situation in which intense, devastating fires burn in the hottest, driest part of the year.

While studies in North America show that fires claim few animal casualties, they strip the landscape of significant habitat, limiting the amount of food and shelter available for survivors. A day before, Legge had sat in her office at another AWC property, Mornington Sanctuary in central Kimberley, pointing to a digital map of fires in the area this year. ''This one was started by a spark from a bulldozer or a grader,'' Legge says, indicating a large purple blotch that represents an intense, late-season fire, east of Mornington. ''And that one was a campfire that got away.'' The gradual movement of Aborigines from the country to cities, coupled with increases in tourists and farming contractors, led to the jump in the number of out-of-control fires. In an attempt to minimise the negative impact on wildlife, the AWC has set up a fire management program, called EcoFire, with neighbouring land managers, including pastoralists and Aboriginal communities. In early April and May, at the start of the dry season when there is still some moisture in the vegetation, the AWC prescribes burns across more than 5 million hectares. While it cannot control the acreage that burns - past rainfall is the key predictor of the proportion of an area that will ignite - the program can alter when the fires burn. ''Burn in August, September [at the end of the dry season] and it's like a holocaust,'' says the AWC chief executive, Atticus Fleming. Whereas prescribed burning in April leaves areas of vegetation unburnt, he says.

The objective is to break up the landscape into a patchwork of burnt and unburnt vegetation that stops the spread of late-season fires and protects areas of old growth vegetation, says Legge, who flew 30,000 kilometres in eight weeks, dropping 50,000 incendiaries over the EcoFire area, earlier this year. ''We call ourselves the bombardiers,'' Legge says. ''Make that the conservation bombardiers,'' Fleming adds. To escape the relentless midday heat on the Artesian Range, the ecologists take refuge under a large tarp. Cross-legged, they hover like excited children on Christmas morning waiting to inspect the calico bags that contain last night's catches. ''What have you got now, Sarah?'' asks Dr Alex James. Legge cups a small marsupial in her hands. The team is not sure if it is a northern brown bandicoot or a much rarer golden bandicoot, whose range has contracted so severely the Artesian Range is likely the last place it exists. Legge consults the books. The animal she holds in her hand is smaller than an average-sized northern brown bandicoot, but it could be a juvenile. She peers inside the creature's pouch to find two sets of black beady eyes. ''It would be very significant to find a golden bandicoot,'' Legge says. After measuring the marsupial's head, tail and a foot, and inspecting its tail, she concludes it is a northern brown bandicoot, but she take some hairs for a DNA sample to confirm her assessment. ''These are just the type of small mammals cats love to eat,'' she says.

Legge suspects feral cats are the greatest threat to the Kimberley's biodiversity. She estimates there are at least 100,000 in central and northern Kimberley. When they opened the stomach of several cats they found they were eating up to 12 animals a night, which equates to about a million native animals being eaten daily by cats. Determined and strategic predators, feral cats often hunt animals thought to be rare in the landscape. ''I remember opening up one cat and it had 10 dunnarts [small carnivorous marsupials] in it,'' she says. ''That's not an animal we catch very often.'' Not only are feral cats effective hunters, they fill a niche in the food chain. ''They can exert maximum pressure downwards but there is nothing controlling them,'' Legge says. She has collaborated with several Australian universities, three national park agencies and the CSIRO on a cat-tracking project that has revealed surprising insights into feral behaviour. So far they've attached GPS collars to 20 cats and recorded the animals' movements over several months. Late last year they found a collared tomcat, Bruce, travelled more than 14km to hunt along the edge of a fire scar. ''It was such a shock for us to see this cat travelling out of his home range, through other cats' territories, to pick off the refugees at the edge of this fire scar,'' Legge says.

Since Bruce, they've witnessed similar behaviour in two other feral cats. While the AWC ecologists have not seen any of these predators in the Artesian Range, Legge is confident they are there. ''They are found across all four corners of the continent, they're in rainforests, deserts.'' A collaborator on cat-tracking program, wildlife conservationist Professor Chris Johnson, believes the role feral cats play in the north closely mirrors the impact red foxes had on mammals in the arid and semi arid woodlands of central Australia from the 1870s to the 1950s. Nineteen species became extinct during that time, giving Australia the claim to the world's worst extinction rate, says Johnson, of the University of Tasmania. The feral cat invasion has been, at least in part, facilitated by the spread of introduced herbivores such as cattle, donkeys and pigs. With most of the Kimberley under pastoral lease, these animals have become ubiquitous across the landscape, including national parks. The grazing and trampling of these animals, both captive and feral, creates large patches of barren, functionless land across the tropical savannahs, destroying the habitat of many small animals in the process.

In an attempt to measure the impact of these introduced species, Legge led a four-year study to destock more than 40,000ha of Mornington Sanctuary. Three years after removing the beasts, the team, which included scientists from Charles Darwin University, the Australian National University and the Northern Territory government, found native animals almost doubled in abundance. While Legge concedes that removing introduced herbivores from the land is not a wholesale solution, they should be moved off conservation land. ''That will be an interesting challenge for parks, because they don't have the staff on the ground to carry out the removal,'' Legge says. The final assault on the Kimberley will be the arrival of cane toads. They have already reached Kununurra in the state's north east. Evidence from other states shows Australia's most notorious pest has a severe impact on several species unfortunate enough to eat them, such as goannas, snakes, northern quolls and freshwater crocodiles. For wildlife ecologist Professor Brendan Mackey, it is the interaction of all the threats to the Kimberley that have created the current situation.''If we don't do something now, it will be too late in 10 years,'' says Mackey, director of Griffith University's climate change response program.

To save the Kimberley and its unique wildlife, a group of scientists and conservationists formulated a priority list of programs and their cost to safeguard key animals. An author of the study, ecology and mathematics professor Hugh Possingham, says a cost-benefit analysis shows the area's wildlife can be secured with an initial $95 million investment, followed by another $40 million each year. He says it is not good enough to just fence off an important piece of land and call it a national park. ''A national park doesn't mean anything unless you manage it,'' says Possingham, director of the Australian Research Council's Centre of Excellence for Environmental Decisions at the University of Queensland. As part of a new conservation strategy for the Kimberley, the Western Australia Department of Environment and Conservation has committed $63 million over the the next five years. It includes $21.5 million for a landscape-scale program of fire, feral animal and weed control. Possingham doubts this will be enough to save many of the region's most vulnerable creatures. He says that if in 10 years several key species have vanished, as predicted, governments can blame no one but themselves. ''We told them what to do, and they chose not to act,'' he says.

For Fleming, the AWC's chief executive, the scale of the problem in the Kimberley is too great for governments to solve alone. ''We've got to do something different if we want to prevent extinctions and save the wildlife,'' he says. The conservancy's model of placing people on the ground to manage conservation areas based on published science is going against the trend in the state's national parks, whose administrators have dramatically cut numbers on the ground. ''How can you effectively manage a national park if you don't have people living there, getting to know the place?'' Fleming asks. ''The wave of extinctions that have swept across northern Australia is crashing on the Kimberley's right now. If we don't act, it will be too late.'' Back at the Artesian Range campsite, the AWC ecologists are preparing for a final night of spotlighting.

''It's a good night for pythons,'' says Alex James, who has already spotted a couple of Olive pythons on the rocky ledge between her tent and the nearby creek. Due perhaps to the victory of hope over experience, she was confident her team would find their rarer cousin, the elusive rough-scaled python. The tracking gods were not to be with with the group that night, but hope lives. Loading Nicky Phillips travelled to the Artesian Range courtesy of the Australian Wildlife Conservancy. Follow Environment on Twitter