The news that Niwa scientists are going to make a proper investigation of the environmental impact of seabed mining will be welcomed by both sides of this debate. New Zealand sits atop a large continental shelf stretching to the limits of its exclusive economic zone and apart from drilling for oil and gas we have barely scratched the surface of its potential mineral resources.

"Scratching the surface" of the seabed would be a fair description of the two mining applications that have been considered by the Environmental Protection Agency in recent years. One company wanted to extract iron sand from mud off South Taranaki, another proposed to scrape phosphate nodules from the a section of the Chatham Rise. Under strong opposition from environmental and fishing lobbies, the applicants were obliged to try to prove that no significant harm would be done to marine life.

The Chatham Rock Phosphate application has been turned down, the Taranaki iron extraction project by Trans-Tasman Resources, initially refused, was given the go-ahead on a second application but environmental groups immediately announced an intention to challenge the decision in the High Court. Groups such as Forest & Bird and Kiwis Against Seabed Mining have been able to argue that too little is known about seafloor habitats and sediment clouds in the sea to properly assess the environmental impact.

Niwa plans to simulate mining in the Chatham Rise using a device it calls a "benthic disturber" and underwater photographic and water-sampling equipment to find out what happens to fish and seabed organisms during mining or bottom trawl fishing. Principal scientist Dr Malcolm Clark says they will be looking for the level of resilience of organisms there.

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It is probably too much to expect that the results will make seabed mining applications more straightforward. Whatever the level of disturbance to aquatic life is found to be, it will be unacceptable to environmental objectors. And the Government is likely to be divided on any ocean mining proposals.

The Niwa investigation has been commissioned by the Ministry of Business, Innovation and Employment, probably before the change of government. In the wake of its ban on future oil and gas exploration announced last month it is surprising the Government is letting seabed mining research go ahead. But it is the right decision.

Minerals are essential in the manufacture of just about all the equipment of modern life, including the digital devices that are reshaping the future. It is one thing for New Zealand to renounce any further wealth from petrochemicals and the many products they provide besides motor fuels, it would be quite another thing to lock up all minerals that might lie in the mountains, valleys and basins of our vast undersea continent.

Resource use requires balanced decisions. Once it is scientifically evaluated, some ecological damage may be accepted.