A popular roadhouse in South Australia that played a pivotal role in the rescue of two kidnapped backpackers in 2016 has closed in protest against what its owner says is government "neglect".

Adam Stewart said the Salt Creek roadhouse in the Coorong was losing up to $300,000 a year due to a crackdown on informal campsites and a lack of infrastructure spending in the region.

He told ABC Radio Adelaide that of the 80 "fenced-in little areas" that had marked campsites in Coorong National Park for 40 years, only about six were left.

A closure notification posted on the Salt Creek Roadhouse's Facebook page. ( Facebook: Salt Creek Roadhouse )

A remote support network

The business is the only roadhouse along the 150-kilometre Coorong stretch of the Princes Highway, and Mr Stewart regularly helps campers who run into trouble including those who become bogged or are caught by high tide.

"Most of them would be avoidable if there was the correct signage," he said.

Salt Creek made international headlines in 2016 when two backpackers who'd accepted a ride to Melbourne were attacked by Morphett Vale man Roman Heinze at a dune campsite.

One of the victims, a German woman, was found bloodied and severely injured by nearby fishermen who took her to the roadhouse.

Mr Stewart then helped police through the dunes in search of her Brazilian companion, who had been found by another group of fishermen.

Mr Stewart said an access track in the dunes "collapsed 10 years ago" and was never replaced; he said a broken concrete table beside the highway took 15 months to fix.

"That was the only facility provided by government at the two-hour mark from Adelaide or Millicent.

"There hasn't been a cent spent from council or highways down here in 30 years and it looks like rubbish in the area."

4WDs damaging 'fragile' terrain

Environment Minister David Speirs said the Coorong faced significant challenges and, as a "fragile, natural environment", it deserved the Government's best protection.

"We have had difficulties around the Salt Creek area in terms of people doing illegal four-wheel driving, so we have closed certain campsites where that has been a big problem," he said.

"It's tearing up that fragile environment, causing huge damage, so we are trying to work out a strategy where we can have central points for camping within the Coorong."

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Mr Speirs said he considered the closures to be "temporary measures", stating the Government had to strike the right balance between preserving the "incredibly sensitive natural environment" and people visiting the region.

He acknowledged the importance of the Salt Creek Roadhouse, and said its staff had helped him in the past due to family connections in Millicent.

"It plays an important role in that district and I want to be able to work alongside Mr Stewart," Mr Speirs said.

"Visitation to the Coorong has gone up in recent years ... but it's not for me to comment on Mr Stewart's business model in terms of attracting people to his business."

Most people stay on-track

Mr Stewart said only a "miniscule" number of four-wheel drivers did the wrong thing, and that if the area received better support and more patronage was encouraged, there would be increased pressure on everyone to do the right thing.

"Yes, it's an extremely sensitive environment but it's also a harsh environment that's constantly getting wind-blasted, sand-blasted and with waves washing over it," he said.

"These people are camping within the first 30 to 40 metres of the beach up from the high tide line.

"The damage we're talking about, nothing is everlasting because it's constantly changing with the weather."

The Salt Creek campsite where two backpackers were attacked in 2016. ( ABC News: Dean Faulkner )

Mr Stewart said the Coorong National Park website had at one time said the park in front of the roadhouse would be closed for three months.

"It ended up being 10 months, and that's the first thing people saw when they visited the Coorong online.

"These little things are costing tourism and driving people away."