Environmentalists are warning we need to protect our wetlands if we want to meet our climate goals.
New Zealand has lost more than 200,000 hectares of our original wetlands, and Forest and Bird is calling for a national plan to restore them. Freshwater spokesperson Annabeth Cohen says despite being “absolutely vital”, wetlands have been treated as “out of sight, out of mind”.
“Wetlands in New Zealand have been drained over the years. Historically over the last 150 years we've seen wetlands drained to make room for agriculture and urban development,” Cohen said.
Particularly valuable for carbon storage are peat wetlands, where waterlogged conditions slow the process of plant decomposition to create peat. Peatlands cover just 3% of the earth’s land surface, but store more carbon than all other vegetation types in the world combined.
On the Hauraki Plains, the Kopuatai Peat Dome stores two-and-a-half tonnes of carbon per hectare every year, 10 times more than a pine plantation.
The problem is when they’re drained. Melanie Dixon from the National Wetland Trust says dry peatlands turn from carbon sinks into carbon producers.
“Once you've drained it, the peat is breaking down. It swaps round, it’s emitting carbon dioxide… it’s suddenly the worst thing for our carbon,” Dixon said.
“If we don't look after [the peatlands] they'll send us into rapid, dangerous levels of climate change.”
It’s estimated dried peatland is responsible for up to 6% of agricultural emissions in New Zealand, but wetlands aren’t part of climate accounting, meaning you can’t get carbon credits for restoring them.
In Waikato 83,550 hectares of former peatland is currently used for intensive agriculture.
“If we hope to meet our goals in regards to climate change as a country we need a national plan to restore our peat and coastal wetlands” Cohen said.
A plan is in place to restore 80 hectares of peat-filled paddocks at Wellington’s Queen Elizabeth Park. The four-year project was brought about after pressure from environmental groups.
Friends of Elizabeth Park chair Russell Bell says re-wetting the land is much more efficient than planting trees to offset the carbon.
“Offsetting is a long-term strategy and we haven't got a long time, go for reducing emissions. This [restoration] reduces a huge amount at the stroke of a pen basically, fill in some drains and you've got it sussed,” Bell said.
“Once it’s restored it'll start building itself into a really good wetland – you’ll see flaxes, toitoi, carexes springing up… It will be fantastic for the public, more of the public will come to this park, but the real benefit is for climate change.”
While Dixon says it’s not feasible to restore all 200,000 hectares of former wetland in New Zealand, alternatives like paludiculture, where crops are grown on wet soil, need to be investigated.
“We need to find alternative uses for some of this land. Not all of it, but some of this land that’s in agriculture is not really sustainable.”