Plans to set up 3000-hectare ecosanctuary in Wainuiomata Lower Hutt have taken a step forward, with a feasibility study from Zealandia's founder.

The project would see 29km of predator fencing around native bush which would then be restocked with kākāpō and other endangered birds.

The study, by Jim Lynch, said it could cost about $42 million over a decade in consents; to build the fence and other infrastructure; and to eradicate pests.

Greater Wellington Regional Council owns the land, but the government would have to pay for the setup cost.

Council environment committee chair Penny Gaylor said the ecosanctuary could add $160m to the local economy over 10 years, and create 16 permanent and nearly 50 short-term jobs.

The council would help maintain and manage the sanctuary, called Puketahā, once it was up and running.

Site too good to let slip

The endangered kākāpō, of which just 200 remain, could find a home there with room for about 150 of the parrots.

Kākāpō were last seen near Wainuiomata in 1905.

Rowi kiwi and hihi, or stitchbird, among other threatened manu māori (native birds) could also live there.

Councillor Thomas Nash said there would be a massive benefit to biodiversity to the area and at popular nearby walking tracks.

"It would be pretty stunning.

"This is the sort of nugget of biodiversity goodness that's too good to let slip for our grasp."

Expanding the kākāpō breeding programme close to an urban centre would lower costs and carbon emissions, the regional council said.

Lynch said the forest in Puketahā was ideal habitat for kākāpō.

"Virgin forest of this kind is incredibly rare in Aotearoa.

"In Wainuiomata, we have an abundance of ancient rātā, miro, mataī, hīnau and tawa but, most importantly, rimu, which covers 85 percent of the site. Kākāpō require abundant rimu to trigger and sustain their breeding," Lynch said.

"The site is surrounded by accessible ridgetops making it well configured for fencing. Having 40,000 hectares of adjacent forest in the Remutaka Range is also an advantage, as it's likely that many bird species will eventually migrate from the sanctuary."

Taranaki Whānui Trust chair Kara Puketapu-Dentice said his iwi was aware of the enormous commitment required to care for kākāpō, should Ngāi Tahu allow the critically threatened manu to return from their takiwā in Te Waipounamu.

"The sanctuary cannot happen without permission and knowledge transfer from their kaitiaki," Puketapu-Dentice said.

"Taranaki Whānui will work alongside its partners, including Ngāi Tahu, to ensure the project upholds our kaitiaki responsibilities as mana whenua and enables the meaningful reconnection of our uri (descendants) to this special place."

The Department of Conservation said the sanctuary had the potential to contribute to the country's biodiversity strategy.

Some challenges to overcome

Nash said there were some tricky problems that needed to sorted.

One was how to fence off the area while still letting fish move up and down the river, and there was a steep section which would be challenging to build a fence on.

Nash said it would be unlikely resource consent would allow them to remove dirt from earthworks, and they would have to find somewhere onsite to carefully and sensitively put it.

But he said the main issue would be whether the government was willing to fund it.

It is possible private philanthropic donors might want to get involved, he said.

There have been concerns raised about the need to clear about 10 hectares of forest to build the fence.

But Nash said the payoff for felling a small number of trees to establish thousands of hectares of predator free bush was worth it.

And he said it would not be necessary to cut down large, old podocarps.

He said the sanctuary would not restrict any of the walking tracks in the area.

Republished by Arrangement