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Saltmarsh a carbon sink opportunity, but Bay of Plenty’s have dwindled

Ōhiwa Habour, between Ōhope and Ōpōtiki, could help soak up carbon, a local forum heard.

Posted on March 27, 2023

As well as being an important habitat for marsh birds and other wildlife, improving water quality and flood resilience, salt marshes may also have implications for combating climate change.

At a six-monthly meeting of the Ōhiwa Harbour Implementation Forum in the Bay of Plenty, chairman Toi Iti pointed to a report received at the previous week’s monitoring and operations committee of the regional council’s on work being done to unlock the blue carbon value of salt marshes.

Blue carbon describes coastal and marine areas’ abilities to sequester and store carbon.

“So we’re looking at it as a possible way that the regional council can look at improving our carbon sequestration. As our scientists and teams look into that, saltmarsh restoration is definitely on the ticket,” Iti said.

The report he referred to, presented to the committee on March 7, stated that there was little understanding in New Zealand of carbon storage in salt marsh.

The council was taking part in a study with Niwa and the University of Waikato to take deep sediment core samples from healthy saltmarshes to develop a blue carbon accounting framework. It was hoped that creating this framework would help provide some financial incentive through carbon credits for farmers to take part in salt marsh restoration.

The report showed that the Bay of Plenty had lost 60% of its salt marsh areas between 1840 and 2000, around 1400 hectares.

While the regional council had been restoring wetland on private and tangata whenua land mostly through grants for plants and fencing, so far, between 45 and 100ha had so far been restored.

A mapping exercise looking into areas suitable for marsh restoration, based on elevation, identified 4887ha of land in the Bay of Plenty with potential for saltmarsh restoration. The majority of this is currently in use as pasture.

A large proportion of these low-lying areas lay in the Whakatāne and Rangitaiki catchment areas though the lack of any large estuaries in these areas made more suitable for freshwater wetland areas than the Tauranga, Kaituna and Pongakawa catchments.

Iti asked environmental scientist Erin Fox to speak about a mapping exercise that had been undertaken by the regional council at Tuesday’s meeting.

“It’s quite a rough tool for the whole region, but it does give us some ideas of areas that are of the right elevation to support salt marsh. That’s something we would be willing to share if it would support some of the work [the forum] are looking at.”


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