A community group set up in the 1980s to protect Western Australia's island paradise, Rottnest, says it is appalled by the erosion damage to the dunes at one of the island's latest tourist developments.

Pinky Beach has been closed since mid-August to allow the operator of the luxury "glamping" resort on its doorstep to replace access stairs and rehabilitate the dunes, following severe winter storms.

But the Rottnest Society, which was set up in 1984 in response to plans for an international hotel and marina on the island, is not satisfied that the sensitive bay on the island's northern side is being adequately protected.

"I've been deeply concerned about the state of Pinky's," long-time society treasurer Trish Bevan said.

"I could see the destruction of the dunes coming."

Call for government help

The society has written to WA Tourism Minister David Templeman, saying the resort should never have been approved at the beachfront location.

It has argued far more "active management" needed to be carried out by the Rottnest Island Authority to protect the area, given the additional visitors the resort is attracting to the beach.

Ms Bevan and society deputy chairman Ian MacRae, a retired town planner, visited Pinky Beach last week to try to survey the erosion damage firsthand.

But they were promptly shown the door by a ranger who explained the beach was closed to allow for the construction work to be carried out on the new access stairs.

Ms Bevan, who has led dozens of tree planting expeditions to Rottnest over her 14 years with the group, was not impressed.

"I think the beaches belong to everybody and to be pushed away, with no signage to stop us, was appalling," she said.

Erosion a long-running problem

It is not the first time the dunes and stairways have taken a battering at Pinky Beach.

Within a few months of the resort opening for business in March 2019, a storm caused erosion damage and forced the closure of the stairways built to keep beach-goers off the dunes.

Resort operator Discovery Rottnest Island said this year's severe winter weather meant most of the northern side of Rottnest had been impacted by coastal erosion.

In a statement, it said it was replacing the access stairs with others that could better withstand severe weather events and was also putting in place extra measures to protect the dunes, including additional balustrades, matting and replanting of native vegetation.

"The environmental protection of Pinky Beach and the land upon which our property sits has always been of the utmost importance to Discovery Rottnest Island and central to all development and design decisions."

While authorities aim to reopen Pinky Beach by September 10 ahead of the busy school holiday period, just around the corner at Thompson Bay South, the erosion is severe.

The state government has allocated over $1.7 million to build a sea wall at the erosion hotspot, with construction planned for April 2022.

Erosion will only get worse: expert

Professor Charitha Pattiaratchi of the UWA Oceans School said this year's conditions had been unusual.

"They have been almost continuous, one after the other, so it is not giving beaches any time to recover and be prepared for the next storm to come," he said.

Professor Pattiaratchi warned erosion along the entire WA coastline was only going to get worse with rising sea levels and more frequent severe storms forecast for the coming decades.

"The state and federal governments do not have enough money to protect all the beaches where we are going to have erosion," he said.

"So somewhere we have to make a business decision and a social decision to say, 'well this beach is going to be far too expensive to protect for the next 50 years,' and walk away," he said.

Hopes environment will be a bigger priority

That is not an outcome Ms Bevan and the Rottnest society want for the island or Pinky Beach.

In the society's latest newsletter to members, it said that while there seemed to be plenty of money for other projects, environmental work seemed to be a low priority for the Rottnest Island Authority.

Ms Bevan, who has been visiting Rottnest since she was a child, said she was saddened by the way the island was heading.

"I think it's our island and it's being taken away from us with expensive development," she said.

"There is less and less interest in the environmental side.

"I feel that it's becoming impossibly expensive for the average family to be part of Rottnest and that saddens me.

Neither the Rottnest Island Authority nor the Tourism Minister were available for an interview.

In a statement, Mr Templeman said the authority was working on a number of projects to better understand and manage coastal erosion on the island, including monitoring erosion, developing a coastal hazard risk management plan, developing site-specific plans and conducting dune stabilisation work.