A project involving multiple groups in Te Tauihu (the top of the South Island) has been hailed as “a revolution” for its part in raising the profile of blue carbon in New Zealand’s Aotearoa.
Around 40 people from across the country gathered in Nelson this week to discuss findings from the Tasman Environmental Trust-led pilot study, which brought together local people from iwi to Cawthron scientists to raise awareness about the importance of improving estuaries in the context of climate change.
Sediment samples were taken in the “Core and Restore” pilot Waimea inlet And Goodbye Spit/Onetahuaas a first step to discover how much atmospheric carbon dioxide is stored in coastal ecosystems.
The carbon held in such marine ecosystems – including mangroves, seagrass meadows and salt marshes – is known as blue carbon.
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Andy MacDonald/Stuff
A Core and Restore team on Farewell Spit extracts sediment cores to test for “blue carbon”.
Some of those habitats worldwide were found to sequester many times more carbon than comparable forest areas on land.
Anna Berthelsen, a marine ecologist at the Cawthron Institute, told the hui that samples taken from two habitat types from salt marshes in Waimea Inlet showed that they contained an average of 38 tons of carbon per hectare down to 40 cm of soil depth.
That meant that an estimated 9,400 tons of carbon were stored in these inlet salt marsh habitats – where they accounted for 250 ha of the 3,462 ha estuary, between Nelson and Māpua.
Andy MacDonald/Stuff
Sediment from Waimea Inlet was analyzed for carbon stocks, as part of the Core and Restore project which has been described by a DOC consultant as “putting blue carbon on the map” in New Zealand.
Samples of seagrass at Farewell Spit/Onetahua — home to about a quarter of the country’s seagrass, according to others’ estimates — showed an average of 17 tons of carbon per ha, and 115,453 tons in total.
Project leader, Lauren Walker, said the findings offered a “first glimpse” of the sites’ carbon sink potential.
Comparisons with sites elsewhere were difficult, with still no clear picture of a national blue carbon range, and the Core and Restore samples are shallower than those at some other sites, she said.
Andy MacDonald/Stuff
A regional team, led by Tasman Environmental Trust, on their way to seagrass habitat on Farewell Spit as part of the Core and Restore pilot project to monitor blue carbon.
The Department of Conservation’s national spokesperson on blue carbon, Helen Kettles, said the project was being offered much more than simply measuring carbon.
A report by NGO The Nature Conservancy (TNC), in which the feasibility of a voluntary blue carbon market in New Zealand, “it wouldn’t have worked out” if it weren’t for Core and Restore, she said.
Competing with TNC’s offices around the world to run the report, the New Zealand branch had to prove that blue carbon was “something that was real, on the ground in New Zealand,” Kettles said.
“The only place where that was real and on the ground was here,” she said.
ANDY MACDONALD / THINGS
The Core and Restore project samples sediment from the salt marsh habitat in Waimea Inlet.
The project’s bicultural approach also helped “win over” the adoption of TNC, Kettles said.
“Having that relationship with an Indigenous culture was something that they really enjoyed because it didn’t happen anywhere else in the world.”
Groups involved in Core and Restore (including collecting the sediment cores) included Ngāti Apa ki te Rā Tō, Onetahua Restoration partners, and Manawhenua Ki Mohua; an organization representing Ngati Tama, Ngati Rārua and Te Ātiawa, as well as Cawthron scientific institute and Beca engineering firm.
The project “used the power of … being connected to each other and the environment” to respond to climate change, Kettles said.
Also included the project as a case study in the government’s greenhouse gas emissions reduction plan last year increased the profile for blue carbonshe said.
“You have been the revolution in putting blue carbon on the map.”
a tea bag studyrun concurrently by Nelson City Council with the help of volunteers, also demonstrated the benefits of “citizen science” in driving estuary restoration, speakers said.
The council said tea bags planted in the Waimea Inlet and Nelson Haven showed that the coastal wetlands contain high levels of carbon, compared to results from similar studies of terrestrial and wetland habitats worldwide.
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Coastal and marine scientist Vikki Ambrose of Nelson City Council along with Nelson Haven water quality scientist Paul Fisher who are surveying sites to conduct research on tea bags.
Hui participants scored Core and Restore highly on social outcomes and adaptability, including new partnerships, knowledge integration and innovation.
Other speakers included scientists who measure carbon in coastal ecosystems, mostly in the North Island, and are involved in calculating credits in blue carbon markets abroad.
The Tasman District Council outlined its restoration work on coastal wetlands, including excavating a channel on part of the Waimea Plains to re-wet the land.
CATHY JONES/included
Wairau Lagoon in Marlborough was one of several coastal wetlands in Aotearoa assessed by TNC as potential recovery sites in a voluntary blue carbon market.
Coastal ecologist Leigh Stevens outlined how an estimated 50% of the country’s salt marshes and most of the seagrass was lost, with estuaries drained to become urban or farmland and broken down by fine sediments, nutrients and pollutant loads.
Estuaries also protected against coastal erosion and “didn’t take much” to be restored — including things like opening up low-lying, low-value farmland so it could flood again, he said.
Project participants would now decide whether to do more testing of local estuaries.