Calls have been made for urgent protection of fragile marine areas in the Marlborough Sounds, which are rapidly disappearing.
In a new report, the Marlborough District Council said that large areas of the Sounds' environmental systems were being seriously harmed by dredging, boats anchoring and the effects of flooding on marine habitats.
Mayor Alistair Sowman said the sites were mainly in Queen Charlotte Sound.
"There have been a number of sites identified in the Sounds that we decided to monitor that had a fragile ecology and this report is quite damning, but they are not marine farm sites - they are sites of ecological value that the researcher decided to put forward for examination."
Mr Sowman said the blue cod habitat, in particular, had been endangered in areas near where forestry run-off had occurred and where large numbers of boats had anchored.
The report, which takes in analysis over a four-year period, was prepared by a Nelson marine biologist.
It was jointly funded by the council and the Department of Conservation and presented to the council's Environment Committee.
Chairman Peter Jerram said the report was a "wake-up call" as the speed of deterioration was frightening.
"Losing 70 percent of the area of significant sites in only four years tells us there are major problems in the way we are treating the Sounds."
The council's regional planning and development committee will now consider the report and use it to guide decisions on how to manage the problem.
"We have a new [Resource Management] Plan coming out which will address this issue for remaining sites of ecological significance but the inner and outer Sounds, in particular, are desperately fragile environments and it really needs the Ministry for Primary Industries to engage with the council and the community to save our sensitive sea beds from on-going decline," Mr Jerram said.