Great Mercury Island owner Sir Michael Fay believes the island and the group it belongs to have a strong future now that they have been declared free of pests.

After four decades of hard slog, the Mercury Islands group off the eastern Coromandel coast are pest- and predator-free.

At a ceremony on Great Mercury Island on Friday, May 13, Minister of Conservation Maggie Barry made the announcement to the delight of the small crowd of supporters, volunteers and Department of Conservation staff.

Barry said areas becoming predator free are the holy grail and it's encouraging to see the passion and drive from the people involved in the project.

Along with David Richwhite, Sir Michael Fay owns Great Mercury Island and he said becoming pest free is a result of decades of work from a lot of pioneers in island rat eradication.

Now that the island has joined the rest of the Mercury group as pest free, with the help of passionate volunteers and co-ordination by DOC, Sir Michael said it is time to look forward.

"We've got a good opportunity sitting here."

He said the next thing is to co-ordinate the Mercury group in a management plan, which could look at further relocation of tusk weta or tuatara.

"There is nothing we can't do if we keep the pests away and get the public support in keeping them off Mercury Island, and then we can transform this place in the decades ahead."

Greater Mercury Island is rich in cultural history. Signs of human settlement date back hundreds of years.

"The New Zealand story is unique in the world. In terms of the last large landmass to be inhabited 800 odd years ago, it's fairly young," Sir Michael said.

"In the New Zealand story, these islands are a very special part of history."

He said while the island has a lot of significance and history, it also has a robust future.

Representing Ngati Hei, Joe Davis said at the ceremony that having the group of islands pest free has a positive effect on the whole of Hauraki.

"For Hauraki, every island that they can restore is a move in the right direction.

"It gives our flora and fauna a way better chance of survival on these islands."

When he purchased the island 40 years ago, Sir Michael knew that the rats, cats and other predators needed to go.

Greater Mercury Island project manager for DOC Peter Corson said it will only take a moment of inattention and the islands would return to square one.

"It's a plea to all the boaties to take some responsibility. A little bit of effort will save these islands."

Instrumental in Great Mercury Island becoming pest- and predator-free, Dr David Towns agreed that while it was one of the most biodiverse places in the country, its future is everyone's responsibility.

"We're starting to deal with the social and cultural aspects of the restoration," he said.

"We're learning how people relate with the environment and we're telling people about the dangers of the pests being on the islands."