STEVE CANNANE, PRESENTER: Outback Australia is battling an ecological disaster.

According to today's estimates, 750,000 feral camels are roaming wild, and there's a warning they could change the environment so fundamentally that dust clouds could envelope Sydney.

In fact, some estimates put the number of camels at 1 million, maybe even more.

Whatever their exact number, for traditional owners they're destroying sacred sites, and farmers are finding it hard to manage their stock.

While it's agreed feral camels are changing life in the centre, a row's brewing between pastoralists and traditional owners about managing the pests.

Conor Duffy filed this report for Uluru for Lateline. And a warning, the story contains some coarse language.

CONOR DUFFY, REPORTER: It's the ancient heart of the continent, and a vista that's inspired and captivated for millenia. But now, signs warn of a foreign invader that's made itself at home. They roam in the shadows of Uluru and large herds are spreading ever further.

JAN FERGUSON, AUSTRALIAN FERAL CAMEL MANAGEMENT PROGRAM: Well the scale of the problem is huge. I'd love to sit here and tell you they can be eradicated, but our history with all sorts of other invasive species is such that I don't believe that's achievable.

ASHLEY SEVERIN, CURTIN SPRINGS STATION: Years ago I was only shooting maybe 200 a year. Now I'm shooting between 1,800 and 2,000 a year. Once where we used to see a bull camel with 15 or 20 cows and a few calves, we're now seeing groups of up to 80 bulls.

CONOR DUFFY: Arial surveys put camel numbers as high as a million, with herds 10 times as large as this one roaming the landscape. But they blend in so well that some say the true figure could be much higher - and with no natural predator to thin the herds, the outback's become their paddock.

JAN FERGUSON: If these camels increase in numbers to such an extent that they create a lot of denuding of the landscape - which they can do when Australia's very dry - the dust will turn up in Sydney and that's not going to be very pleasant for anybody.

CONOR DUFFY: For now, the damage is being felt much closer to home. Traditional owner and artist Rene Kulitja gave Lateline a rare visit to a sacred site. Called Walla Spring, it's the only reliable water for about 100 kilometres. Camels are drinking it dry and making it unsafe for humans to drink.

RENE KULITJA, TRADITIONAL OWNER (translated): I want to protect this waterhole. If the camels were isolated away from it, they wouldn't come here for water. This is people's drinking water, so we safeguard it.

CONOR DUFFY: It's hard for Rene Kulitja to continue cleaning Walla, but she sticks with the back-breaking work.

Government scientist Jayne Brim-Box and Pat Hodgins are chipping in, and regularly come and check on Walla. They're shocked by the damage the camels have done to their remote sensor cameras. Their vision shows the camels spending entire days at the springs, plundering the precious water so crucial to native wildlife.

JAYNE BRIM-BOX, SCIENTIST: What's going to happen as it dries out, and it eventually will, we'll just have ... I call it Dante's ecological inferno. I've seen it firsthand. In places like this the impacts are profound; and these places are so remote from cities and it's such small places that it's hard to get the message out, that the local damage can be profound.

CONOR DUFFY: As big as the camel numbers out here are now, the conditions out here are just so perfect for camels that most experts agree the herds are going to get even bigger, and there will be even more camels in the outback.

That's also bad news for local cattle producers Lyndee and Ashley Sevren. Their ability to control their herd of prime steers over a huge station has been made harder by the camels and the bill's already running to hundreds of thousands of dollars.

LYNDEE SEVERIN, CURTIN SPRINGS STATION: The feral camels are our biggest issue. They're our biggest management issue in running the entire property. So, the station is just over 1 million acres in size. We're heading out towards the WA border in the NT; we're in marginal country at the best of times.

CONOR DUFFY: Ashley Severin has had to replace hundreds of kilometres of fencing and make it bigger and camel-proof.

ASHLEY SEVERIN: We build it this high ... here comes a camel to a cattle fence - (acts out breaking through fence) and here we go. So we build it this high, he goes, "Jeez".

CONOR DUFFY: This harsh, remote country may be great for camels, but that distance and lack of development mean Ashley Severin's trial at making money out of the ferals didn't add up. He said herding wild animals and building special enclosures and trucks to transport them is too expensive.

ASHLEY SEVERIN: I can't control the camels so why am I going to buggerise around and put a camel in a yard to get $200? Only cost you $1.75 for a bullet.

LYNDEE SEVERIN: There should be and must be and will be camel industry based around meat, fat, hide, toe nails, milk - but it can only viably be based on a domesticated animal.

CONOR DUFFY: The Severins feel their management efforts are being frustrated by the neighbours.

ASHLEY SEVERIN: We uphold - or try to uphold - our end of the bargain. We can't keep up with what happens on Aboriginal land because they don't have to be responsible to anyone. And I bet you don't put that in the fucking film!

CONOR DUFFY: Many seasons are likely to pass before central Australia comes to grips with the problem. But the manager of the camel program says collaborations are forming, and a huge amount of work has gone into getting permission to cull right across the vast landscape.

JAN FERGUSON: The actual land clearances, which are enormous - to get landholders individual permission to work on their country over 3.3 million square kilometres - is massive. There are 75,000 less camels than there were.

CONOR DUFFY: Plenty more changes for a silent witness that's already seen many of them.