Farmers building wetlands on their land are urging the Government to do more to explore their potential to absorb carbon.
A Cabinet paper released to Newshub said New Zealand's reliance on exotic forests to remove carbon from the atmosphere is risky and could be costly, and recommends exploring other options like restoring wetlands.
New Zealand has lost 90 percent of its original wetlands, with most of them turned into farms. But now, many farmers are working to reverse that trend.
Donna Cram and her husband Philip built a wetland three years ago to improve water quality.
"The purpose was to do the right thing for the environment and for our farm," said Donna, a farmer in south Taranaki.
Their wetland is monitored regularly by scientists who say this is a hardworking swamp.
"As well as removing nutrients, they're also sequestering or storing carbon in the wetland, and they're also reducing the greenhouse gas emissions from those contaminants as they pass down through the waterways," said Chris Tanner, NIWA aquatic ecologist.
That puts wetlands on Climate Change Minister James Shaw's radar.
"At the moment, in order to draw carbon dioxide out of the atmosphere, we really only have one technology available to us and that's planting trees," he said.
The newly-released Cabinet paper said New Zealand's reliance on forests to remove carbon from the atmosphere has risks and costs. It recommends the Government incentivise other carbon removal activities, like restoring wetlands.
"We know that there are other things that also draw carbon dioxide out of the atmosphere, such as mangroves, wetlands, peatlands soil sequestration and so on," Shaw said.
The problem is that while wetlands absorb carbon and store it, they also emit greenhouse gases, so their benefit is hard to measure.
"We certainly have to do some more work to be able to quantify those benefits from the on-farm wetlands given the huge diversity of different situations that they're operating in," Tanner said.
He Waka Eke Noa, the farming partnership tasked with deciding how to cut emissions from the primary sector, decided we don't know enough about wetlands' ability to suck carbon from the atmosphere, so left them out of consideration as a way farmers could offset their emissions.
The Government said that work is underway, but farmers said it needs to move faster.
"As farmers, in order to make the investment in a wetland, we need to know how much carbon it will sequester," Donna said.
Restored peatlands like Sinclair Wetland near Dunedin have a better chance of quick gains for cutting emissions, so the Government's looking to include them in our emissions accounting.
"They tend to be rainfed and be very low nutrient and quite acidic, so they tend to store a lot of carbon and a lot of the plant material that grows in them gets accumulated in the bottom of those wetlands and builds up the peat," Tanner said.
In the future, new systems like the proposed biodiversity credit scheme could be a way for farmers like the Crams to cash in on their hard work. But for now, they're reaping the environmental benefits of their wetland.
