The backers of a plan to plant and protect native forests say sucking carbon out of the atmosphere using homegrown projects could be cheaper than buying carbon offsets overseas.
They are taking their concept to the COP28 climate summit, which starts on Wednesday - but say they need government backing.
The government has committed to lopping around 150 million tonnes off New Zealand's greenhouse gas emissions during the decade to 2030. Based on current policies, around two-thirds of that will have to be met by buying offshore carbon savings, costing billions of dollars.
The rationale is that taking more action inside New Zealand is even more expensive than meeting commitments offshore.
But lobby group Recloaking Papatūānuku says investing in indigenous trees could suck in the equivalent of 20 times New Zealand's annual greenhouse gas emissions between 2024 and 2100.
Costings released by the group on Tuesday said the price per tonne of carbon removed could be around half what the government would pay to offset emissions using overseas projects - $32 a tonne versus an average of $60 for offshore credits (under Treasury's projections).
The whole projected cost of the project between now and 2050 would be $8.5-12.1 billion, said the group - but it would only work if the government bought in.
Meeting climate targets
Recloaking Papatūānuku's estimates included only land the group said was suitable for planting, and excluded high-quality cropland and other land that was not beneficial to plant in native forest. The resulting land totalled around 5 million hectares, and the group aimed to reforest at least 2.1 million hectares of that.
The aim was to create healthy forest, through a mix of planting new seedlings on some land, regenerating scrubland, and better protecting existing forests from deer, pigs and goats. Culling these hoofed animals would also reduce methane emissions, the group said, but that was not factored into the estimates.
That group said the project could help New Zealand meet its international climate obligations under the Paris Agreement, as well as generate jobs, help biodiversity and protect landowners downstream from slips and flooding.
Eventually, the trees could suck in more carbon dioxide than New Zealand needed to meet its climate targets, and could be available for selling credits to other countries, it said.
However, new trees take a while to reach peak carbon-sucking potential. The group's estimates showed the project would only supply a minority of the carbon savings needed between now and 2030, the period of New Zealand's first commitment under the Paris Agreement.
In the short-term, most gains would come from protecting existing forests from introduced predators, which eat large amounts of biomass, it said.
Even with a mass forest push, New Zealand would still likely have to pay billions of dollars for carbon offsets from other countries to meet its domestic shortfall between now and 2030. Treasury has not provided a targeted projection of what offshore credits could cost beyond its very wide projection of anywhere from $3b-$23b.
Help for landowners
Recloaking Papatūānuku put forward different suggestions for funding the plan, including landowners getting government grants and then sharing carbon credit income with the Crown, or taking Crown loans for planting to be repaid from carbon credit income. Its preferred option was for Recloaking Papatūānuku to be funded to plant a mix of indigenous forest and shrubs on 2.1 million hectares over the next 10 years, then to care for and protect forest from predators for decades afterwards.
Rangi Ahipene, one of the experts consulted for the project, said having access to funds for reforesting land would help keep land in Māori ownership, if it was not economic to own at the moment. The only alternative otherwise was to sell it, he said. He has heard feedback from landowners in his iwi land trust for years that they would like to look at alternatives to planting pine trees.
"The feedback was, 'We'd love to do it, but does it pay for itself?' And my understanding of Recloaking Papatūānuku is, it does.
"Māori trusts spend millions dealing with pests, and Recloaking Papatūānuku… goes some way to solving that."
Sir Stephen Tindall, one of the project's backers, said he was concerned about the future for New Zealand business unless the country started stepping up with real climate action.
"I believe we will start to fall behind unless we have something we can point to as a country that we are making a difference.
"We agree with the Climate Change Commission that the first thing we should do is reduce fossil fuel emissions… but what are we going to do about the carbon that's already there?"
Rob Morrison, chairperson of Pure Advantage - one of two groups backing the scheme (along with Tāne's Trees Trust) - said New Zealand's climate commitments were binding.
"It's possible we walk away... but if we do, we think the damage.. to our economic outlook will be catastrophic. There's no country in the world that relies on clean and green credentials as much as New Zealand does.
"We didn't make the progress we wanted to make under the last government and we can't afford to slip back under this government."