Barrister for the joined parties of the Wilderness Society, Tasmanian National Parks Association and two individuals, Juliet Forsyth, said proponent Daniel Hackett's evidence regarding the impact of the proposal on the wilderness values of the national park was "more opinion than evidence".

The Resource Management and Planning Tribunal is hearing an appeal from Mr Hackett whose development application for visitor accommodation on Halls Island, at Lake Malbena in the Walls of Jerusalem National Park, was rejected by the Central Highlands Council earlier this year.

In the final two days of the hearing on Thursday and Friday, the tribunal heard evidence from two experts regarding the impact of the proposal on wedge-tailed eagles and closing arguments from the parties.

In her closing submissions, Ms Forsyth said because Mr Hackett was set to gain financially if the appeal were to succeed his evidence must be considered to have been given to the tribunal in self-interest.

"Mr Hackett has no formal qualifications. His only experience is as a guide and business operator," Ms Forsyth said.

Ms Forsyth said the development "significantly underestimated" its impact in a number of areas, including the proposal that only 10 litres of water would be used per day.

"What happens if [visitors] are not satisfied with one shower and only [one hot meal]?" Ms Forsyth said, referring to the $4250 per person price tag for the three night, four day trip.

"If the demographic is as Mr Hackett proposes, the water use will be much higher."

Lawyer for the Central Highlands Council David Morris said the council voted against the proposal due to the use of helicopters ferrying visitors to and from the island being classifiable as a transport depo.

Mr Morris said the distributing of passengers was a "prohibited use" under the management act.

"The pick up and drop off of passengers - it does not allow it," Mr Morris said.

Mr Morris also stated the council's position in regards to the proposal's impact on eagles was any risk was unacceptable.

"It's too much of a risk to take in one of the most pristine environments," he said.

Mr Hackett's lawyer Shaun McElwaine raised a number of arguments around the issue of jurisdiction.

Mr McElwaine said the tribunal was not able to determine criteria such as the social benefits or the financial viability of the proposal.

"It's subject matter that strays beyond [planning]," Mr McElwaine said.

Mr McElwaine said the tribunal had to consider the dual character of the land management acts, both state and Commonwealth, for Lake Malbena.

"If the Federal [Environment] Minister has said there will be no detrimental impact on eagles, it's not up to the tribunal to draw a contrary conclusion," he said.

The tribunal is expected to hand down its decision in September.