Greening the Red Zone says it can turn 428 hectares of red zoned land into native forest for $2.5 million.

Christchurch's residential red zone could be turned into native forest for $2.5 million, a group in favour of the idea says.

Greening the Red Zone submitted its proposal to Regenerate Christchurch on Friday, saying 80 per cent of the Otakaro/Avon River Corridor, in the city's east, could be turned into forest for that price.

The estimated cost, spread over five years, was based on the Tuhaitara Coastal Park in North Canterbury.

SUPPLIED This was Avonside in 2015...

School and community groups have helped plant and maintain the 575-hectare park, between the Waimakariri River mouth and Waikuku, as part of a project to return it to native coastal forest.

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"Ongoing annual costs in terms of management, labour and capital expenditure are likely to be around $250,000 per annum," the Greening the Red Zone's proposal says.

SUPPLIED ... Greening the Red Zone wants it to look like this by 2115.

"As at Tuhaitara, we anticipate that significant volunteer input will help to keep costs low."

The proposal, called the Avon-Otakaro Forest and Wetland Park, says the large forest would attract native birds like tui, ruru and kaka.

"This area must essentially be continuous, without substantial interruptions by anything more than pathways or necessary roading."

SUPPLIED Greening the Red Zone's plan for a native forest park in the red zone.

It would provide a flooding buffer between the Avon River and housing. It would absorb pollution, the proposal says.

Anyone could access the proposed park, which would have paths for walking and cycling.

Though it would take up most of the available area, the forest would tie in with other red zone developments.

It would be "most successful" if other red zone proposals that changed the landscape or were "indifferent" to nature did not encroach.

Regenerate Christchurch chief executive Ivan Iafeta said the forest could be complimentary to other proposals the organisation had received.

There are more than 20 red zone proposals.

Others ideas include a flat-water facility for rowing and other water sports, surf and whitewater parks and a 38-hectare Eden Project eco-tourist attraction.

The Eden Project was estimated to cost $90m to $120m. There were no estimates yet for the flat water facility, but a similar project pitched 10 years ago by Canterbury Rowing was proposed to cost about $30m.

Regenerate's letter of expectation includes investigating building an international open water course.



"One of the potential benefits from the proposal from Greening the Red Zone are the wellbeing benefits that it offers to people who live around the area as well as visitors," Iafeta said.

"Potentially it's a viable option for the red zone to be considered."

The Greening the Red Zone proposal said the forest would take 30 to 40 years to reach maturity.

"During this time it will provide an ever-changing, regenerating natural environment that will benefit all of Christchurch.

"For example, Travis Wetland was established only 20 years ago and is already a much-loved and often-visited natural attraction in the east. Kahikatea and totara planted when it was established are now fruiting and birds as rare as bittern are breeding there."

Regenerate would assess a shortlist of options for public exhibition, then release consultation documents and draft regeneration plans in September.