Harbour Restoration Group member Peter Hayden said the organisation had been "galvanised into action" after sitting through Otago Regional Council hearings on Port Otago's application to dredge material from the lower Otago Harbour.
He said the group, which includes members of fisheries, wildlife, ecological and recreational organisations, believed the fine material dredged from the harbour could be used to build a "necklace" of small islands up to 100m in diameter at the Portsmouth Dr end of the harbour, and a much larger 30ha island near Ravensbourne or Macandrew Bay.
The proposal was not an original idea. Mr Hayden said it came from a study by the Dunedin City Council, Port Otago, the University of Otago and the Otago Polytechnic in 1991, which was aimed at creating a vision for the future of Dunedin.
The concept was dredged up again after finding favour with the Harbour Restoration Group.
Mr Hayden said it was still early days and everything was hypothetical, but the man-made islands could create a tremendous asset for the city and boost the harbour's ecosystems.
The larger island could be planted out to support wildlife, while the smaller islands could be used for recreational fishing.
The islands could be positioned to create a windbreak for rowers on one side of the harbour, and more windy areas for kite surfers, wind surfers and sailors in other parts of the harbour.
One of the greatest beneficiaries would be the intertidal habitat, he said.
"The intertidal habitat has gone in the past 100 years since land was reclaimed for the city.
"Those areas, which popped out of the sea at low tide, created the basis of the coastal marine food chain and contributed to the health of the harbour."
The islands could help re-establish these areas, he said.
In a submission to the ORC hearing panel, University of Otago emeritus professor of plant ecology Alan Mark shared the considerable concern for the proposed dumping of up to 7.2 million cu m of material in the open ocean close to the coastline, and supported the Harbour Restoration Group's idea.
He said the vision had been discussed with Port Otago officials, and the need for appropriate feasibility studies had been raised.
He brought the issue to the hearing panel's attention in the hope it would provide an important offset for a later stage in the proposal.
He said the issue had not been addressed in the Port Otago application, the draft management plan or the ORC's staff report and recommendations, but he believed it may be able to be considered by the panel during the hearing.
