Originally scheduled to conclude on Friday, the appeal hearing will run for an extra two days in August to allow for additional evidence to be provided before the Resource Management and Planning Tribunal.

The tribunal is hearing the appeal of proponent Wild Drake whose development application for visitor accommodation on Halls Island, at Lake Malbena in the Walls of Jerusalem National Park, was voted down by the Central Highlands Council earlier this year.

More from the Lake Malbena appeal:

On the fourth day of sitting on Thursday, the tribunal heard from planning consultant David Barnes that the proposed development would likely deter other users from continuing to access Halls Island.

Although the camp would be vacant for 240 days of the year, Mr Barnes said the proposed frequent use of the island in the summer, between November and May, amounted to the area being "permanently occupied".

Mr Barnes said the camp's "permanent seasonal facility" would encourage people seeking to access a recreation zone to go somewhere else.

"I consider that an adverse impact," he said.

Under questioning by solicitor Paul Turner, who was representing the Parks and Wildlife Service and Attorney-General Elise Archer in the appeal, Mr Barnes said this view was his expert opinion based on his review of the evidence.

Engineer Gustaf Reutersward, whose expertise was in environmental acoustics, told the tribunal, although the proposed helicopter path for taking guests onto Halls Island did not go through the World Heritage Area, the wilderness area would still be impacted.

"The helicopter noise will be audible in the wilderness zone," Mr Reutersward said.

The tribunal did not hear oral evidence from Parks and Wildlife Service Northern regional manager Chris Colley, however, his statement was tendered for consideration.

The hearing continues.