Richard Robinson

The stuff of life

There are places in our seas where the great, whirring cogs of the world hold still. Where the process of decay pauses—for your lifetime, for your children’s, longer—and carbon sleeps, tucked safely away in the sludge. In New Zealand these places are the fiords, the ocean deeps, and the spongy, muddy fringes of our coastlines. And we’re only just beginning to understand them.

Written by       Photographed by Richard Robinson

The multicorer—an instrument designed to take samples from the seabed while barely disturbing it—is carefully lowered into Doubtful Sound.

With a clank and a shudder, the multicorer shuffles off the University of Otago’s scientific vessel Polaris, splashes into the fiord, and sinks slowly out of sight. Looking like a metal spider or miniature moon-lander, the expensive American-made instrument is a futuristic collection of weights, springs, wires, stainless-steel legs, and transparent plastic cylinders. It’s designed to gently land on the seabed and take four simultaneous samples, easing in and embracing the top layer of sediment and the seawater just above it.

“The first time we did this, we were so nervous,” says expedition lead and Otago earth scientist Chris Moy. “We didn’t want to lose it somehow.” All around, the November rain falls into the fiord—as it has all day long, and all yesterday, too. The sheer cliffs of Hall Arm in Doubtful Sound/Patea are ribboned with lacy waterfalls, their collective roar easily audible over the boat engine’s rumble. Leaves speckle the water’s dark surface, and the occasional log floats past: carbon moving from forest to sea.

After a few minutes, the hydraulics winch the multicorer back up. It doesn’t always deploy properly, but this time, as it breaks the surface, Moy’s relieved. “Got mud!” he shouts. Sediment the colour of coffee grounds meets seawater halfway up each cylinder.

By the end of this three-week expedition, Moy and his team will have dropped the multicorer a dozen times in four fiords from Tamatea/Dusky Sound to Kaikiekie/Bradshaw Sound, and they’ll use other devices to collect longer cores of more deeply buried sediment. They hope that this mud will help to answer the question of just how much carbon is locked up in New Zealand’s various fiords—and just how secure those vaults really are.

“We think the equivalent of 10 to 20 per cent of New Zealand’s carbon emissions are being sucked down by Fiordland’s fiords and forests every year,” says Moy’s collaborator Rebecca McLeod, a marine ecologist at Otago. “We don’t really know anything about how it does that, or how vulnerable that might be as the climate and ocean conditions change in the future.”

The Otago team also use other devices to take much longer, deeper cores that enable them to look back in time.

The sea and the air have been playing pass-the-parcel with carbon for aeons. Algae and phytoplankton photosynthesise, drawing in carbon dioxide from the surrounding ocean and in turn from the atmosphere. When a plant dies in the sea, marine microorganisms break it down—just like scraps rotting in your compost—and the carbon dioxide escapes again into the atmosphere.

Some specific ecological nooks, however, can trap carbon long term—and those marine sediments provide the largest store of organic carbon on Earth. When it’s buried in the mud beneath fiords, estuaries, mangrove forests, seagrass beds, salt marshes, and in the deep ocean, the carbon is kept out of the atmosphere, and doesn’t contribute to heating up the planet—it’s safely held tight by the sea.

It’s estimated the oceans have absorbed around 40 per cent of the carbon dioxide humans have emitted since 1850. New Zealand seas, our experts estimate, are holding on to about one per cent of the world’s seabed carbon. That’s 2.24 billion tonnes.

Around the world, scientists, policymakers, and companies are increasingly interested in this blue carbon. And in New Zealand, a multitude of universities, NGOs, iwi Māori, communities and commercial start-ups are beginning to investigate how much carbon our salty sinks hold, how we might prevent their loss or help them to capture more—and whether there’s big money to be made.

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On Polaris, despite the weather, there’s a party atmosphere on deck. An Italian pop song is playing, and half a dozen people in waterproof overalls are huddled over two cores. The sediment in each tube is fine and silky, the consistency of chocolate ganache, and it’s a deep, glossy, pāua-foot black—a sign of its rich organic content. “This is why we come here to study the carbon, because it looks like this,” says master’s student Luke Whibley, wielding a thick slug of the mud on a metal paint-scraper.

Fiords are carbon hotspots—all over the world, they bury more organic carbon per square metre than any other ecosystem. And early atmospheric studies suggest that New Zealand’s fiords are in a class of their own, packing away carbon even faster than those in Norway, Scotland, Canada, Greenland or Chile. On a map, our fiords are a series of insignificant-looking claw marks on one stretch of coast. Yet they account for eight per cent of all the carbon held in New Zealand’s vast sea sediments.

“You couldn’t invent a better carbon burial system than Fiordland,” says Moy. There’s the rain, perhaps 10 metres of it per year, driving the growth of a luxuriant year-round rainforest—and then, during storms, whooshing leaves and logs and carbon-laden soil straight down the steep valleys and into the fiords, scooping up marine plants and animals as well on its way to the depths.

On board Polaris, the University of Otago’s Rob Smith works in the wet lab.

Then there’s the Alpine Fault and a network of smaller faults, lurching in regular earthquakes that shake still more organic material into the sheltered seas. “The carbon just gets shoved in there really quickly, so it doesn’t have the chance to break down and get released as it drops down through the water column,” says McLeod. The forest rapidly regenerates on the bare slopes—that rain again—like a conveyor-belt pulling yet more carbon in from the atmosphere and storing it in wood, leaves, soil.

Importantly, as a national park, that forest is allowed to grow unmolested. At the same time, the marine environment is relatively well protected via marine reserves, special fishing restrictions, and a group called the Fiordland Marine Guardians, of which McLeod is the chair.

Finally, there are the qualities of the fiords themselves. Deep in the middle but shallow at their entrances, they hold carbon-rich sediment undisturbed at the bottom. Down there it’s stagnant, with not much oxygen—an inhospitable place for the bacteria whose job it is to break down organic matter and release carbon dioxide. It’s an almost-stasis, a kind of fortuitous pause in the flow of the carbon cycle—trapping the potent greenhouse gas out of harm’s way for centuries or even millennia.

Sulphur-producing bacteria thrive in the anaerobic mud instead, making the slick dark sludge in the core smell like Rotorua—though “we’ve definitely sampled stinkier”, says master’s student Jorgee Robb, using a spoon to scoop up a dollop of core.

McLeod adds that deep inland, at the carbon-rich heads of some of the fiords, bubbles of hydrogen sulphide can sometimes be seen wriggling to the surface. “It’s like the whole fiord farts.”

The researchers scrape pucks of mud from the core, layer by layer, then save them in plastic tubes, bags, and aluminium-foil packets folded over like origami. “They get sliced and diced and sent all over the world,” says McLeod. To Moy, the cores are “time machines”. From them, we can glean which fiords, or which parts of them, store carbon fastest, and where that material comes from: trees, seaweeds, soil, or algae. Chemical analysis can also reveal how carbon sequestration rates, sea-surface temperatures and even wind speeds have changed over the centuries. “You can build all of that up by looking at the secrets hidden in the mud,” says McLeod.

Knowing the past could help predict the future. For now, Fiordland’s mud is a giant carbon sink hundreds of metres thick. But as the Arctic’s thawing permafrost is  demonstrating, a changing climate can flip a sink to a source, heaving carbon invisibly into the skies.

Jorgee Robb (left) and Rebecca McLeod examine the carbon-rich mud and seawater drawn up by the multicorer.

Moy and McLeod also plan to investigate whether the Lake Manapouri tailrace—the 300 to 550 cubic metres of fresh water released per second from the hydropower station into the head of Doubtful Sound’s Deep Cove—could be destabilising the fiord’s enduring carbon sink. At full capacity, the tailrace is New Zealand’s second-largest river by volume: “it really is a river on top of the sea,” says McLeod.

The Otago team will use mud samples from this spot to establish whether the arrival of the artificial current, in the 1970s, altered carbon sequestration rates or even reversed them. “If it was found that it actually has resulted in carbon being emitted into the atmosphere,” says McLeod, “it might change the way we think about clean green energy from this particular hydro station.”

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For now, the fiords hold on to many of their secrets. But the shallows are easier to study: we know much more about how carbon works in coastal environments like mangroves, salt marshes and seagrass beds. Restoring or expanding them is one of the best ways we know to suck extra carbon out of the atmosphere.

And when they’re healthy, they hum along. According to international research, these shallow-water habitats can haul in carbon up to 55 times faster than tropical rainforests do, and hold up to four times as much carbon in their soils per hectare (though that storage varies significantly across individual places and species).

Everywhere, these ecosystems are at risk from development and sea-level rise. In New Zealand, we’ve lost 90 per cent of our wetlands, including the salty ones.

It’s January 2023. The tide is out in Nelson and little clumps of rimurehia, or seagrass, lie flat in the estuary like trampled pasture. A group of Cawthron Institute scientists are on their knees in the mud, searching through the tough, slender seagrass blades for tiny flowers.

“Once you get your eye in they can be pretty obvious,” marine ecologist Dana Clark says, her wetsuit booties sucking at the silt. “The blades are thin and the flower is a bit fatter. It’s actually easier to feel for them.” She takes a few strands of the fronds and runs them between a muddy thumb and forefinger, trying to perceive the tiniest of swellings.

When the tide is in, this spot, Nelson Haven, is a pretty, calm expanse that reflects sunsets and draws windsurfers and paddleboarders, its millpond blue spreading into the sky. Tide out? Just mud, to most people.

But the seagrass which grows here is a humble powerhouse. It is habitat and food for fish and a feeding ground for wading birds. It takes up contaminants such as metals, and absorbs nutrient runoff from land. When seagrass is healthy, it buries carbon, stabilising it amongst its interwoven roots. But when the meadows die out—as they are now doing all over New Zealand, smothered by river-borne sediment or dug up for our reclamation projects—the carbon goes back into the atmosphere.

After half an hour on hands and knees, one of the group finds a single seagrass flower, and Clark demonstrates how to ease open the fronds a little to see a slight difference in form. It is so much smaller than you’d think. The flower is a pale spike that catches motes of seagrass pollen dispersed in the water. But when seagrass meadows are struggling and the water is full of sediment, that job is a lot harder.

Fiordland’s endless rain, landslides, and steep-sided fiords all help channel huge amounts of plant material into the ocean. This tree’s carbon will be broken down by bacteria and marine animals. But eventually, some of it will end up buried in the seafloor, where it will become part of the fiords’ enormous, ancient carbon sink.
Seagrass sways in the current at Snells Beach, north of Auckland. Its deep root system buries carbon in the seafloor, but only if the bed stays alive. Pollutants and sediment from land threaten the seagrass or block the light it needs to photosynthesise.

Half a year before this seed hunt, a storm thrashed Nelson and sent plumes of silt, including runoff from newly cut forestry, down into these estuaries. Clark points out the patches that remain of the once-flourishing seagrass meadow. “The sediment hasn’t moved as much as I was expecting it to,” she says. In Delaware Bay, a few kilometres away, the sludge formed a film on the seagrass clumps, and the tides did not wash it off.

The plants’ roots usually trap particles in the water. But they can’t cope with too much; by themselves, these meadows may not recover. “It’s like a tipping point,” Clark says. “Once you lose too much of it, it won’t come back.” This estuary alone has lost half the intertidal seagrass it had in 1840. Many other meadows around the country have gone under completely, releasing their stored carbon as they succumbed.

But what if we could find a way to regrow them? That’s why these scientists are picking flowers: for the seeds. Seagrass is a cryptic plant, Clark says. Until recently we thought that the single species of seagrass in New Zealand, Zostera muelleri, flowered only rarely. Scientists believed it mostly eschewed seeds, instead reproducing by sending out rhizomes.

But then an Australian team started using seeds to restore their seagrass meadows—the same species as New Zealand’s. Clark watched with interest. The Nelson team discovered that seagrass flowers had in fact been spotted in estuaries around New Zealand, and in the summer of 2022, interns went out hunting and came back with exciting news. The seagrass in Cawthron’s own backyard was flowering. Supported by nine funders and mana whenua, the team started trying to use the seeds to restore Nelson’s struggling  meadows.

Until recently, scientists thought our seagrass mostly reproduced by sending out rhizomes—creeping underground shoots. Now, they’re learning how to germinate the tiny, inconspicuous seeds, and hope to teach communities how to do it at scale.

Scientists in the US have had success using such seed-based restoration; they grew back 3,500 hectares that had been lost to a fungal wasting disease, using a highly automated system of mechanised harvesters. The Cawthron team are using buckets and fingertips, but they also have help from their Australian colleagues in figuring out how to sterilise, store and germinate the finicky seeds. Germination, for example, takes several pulses of fresh water—the equivalent of big summer storms that tell the seagrass it’s time to go.

The Cawthron scientists found 100 flowers that January day in the mud, and added them to the 500 or so others they collected at three estuaries that summer. They stored the flowers until the following spring, when PhD student Ellie Brettle trialled various germination methods, tweaking conditions such as the temperature of the room and those gushes of fresh water.

In late 2023, the team went back out collecting, and they brought back a bounty: 5000 seeds, their biggest haul by far. A few months later, they had not only germinated some of these seeds in aquariums lined with their home sediment, but had also grown their first seedling, a tiny three-leafed plant they dubbed Seymour after a botanical character in Little Shop of Horrors. Seymour was sort of an accident: the team weren’t trying to grow seedlings just yet. He was three months old as this magazine went to press.

As they work to coax other seedlings from the mud, the team keep one goal in mind: to come up with a blueprint for regrowing meadows from seed, so that communities can one day do it themselves. It will take a lot of people kneeling in a lot of mud, but estuaries in Nelson and all over New Zealand might once again be covered with the olive-green fronds, providing fish habitat, stabilising marine sediment, and taking up carbon, rippling in the tidal waters like a tiny forest.

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Coastal restoration has huge payoffs for plants, animals, people and climate. But it’s expensive and time-consuming. Land prices are sky-high, returning “productive” land to nature often means sacrificing income, specialised tools are needed, weeds grow like wildfire, government support is limited, and through all of it, people have to spend days, weeks, years wading in the muck.

That’s where the carbon market comes in. There is increasing hope that we could actually make money from restoring our blue carbon sinks—those salty, swampy places where land meets sea, so good at holding carbon still.

It’s January 2024 in the Bay of Plenty, and mare’s tail clouds flick across the high-summer blue. Seven hundred years ago, the Te Arawa waka came ashore around the point at Maketu. Those early arrivals would have quickly discovered the rich food basket of Te Wahapū o Waihī—the Waihī estuary. Seagrass carpeted 80 per cent of the shallow sea floor, and hundreds of species of plants thrived in the edging salt marsh.

Even 60 years ago, when Bay of Plenty regional councillor Te Taru White (Ngāti Pikiao) was a boy, the estuary was a place of abundance and connection. He used to camp here with his whānau and gather pipi and watercress, tuatua and tuangi/cockles, sharing kai and kōrero with his community. “No longer can we do that,” he says. “That is a travesty.”

Local students Te Pohoi Ngawaka (10), Tukzee Komene-Williams (12), and Damien Ngakau Petley (13), examine seeds taken from estuaries around Nelson, with Cawthron scientist Ellie Brettle.

After half a century of drainage, forestry runoff, and dairy and horticultural intensification, Te Wahapū o Waihī is paru, polluted—its shellfish toxic, its salt marshes high and dry, its rivers unnaturally straight. The seagrass beds have withered, now covering less than a hectare. E. Coli bacteria are present at five times safe levels, and high nitrate concentrations place Waihī among the top-five most contaminated estuaries in the country.

“I could cry,” says University of Waikato marine scientist Kura Paul-Burke (Ngāti Whakahemo), “but kaitiakitanga denotes action.” So to set things right, the catchment’s five iwi—Ngāti Whakahemo, Ngāti Whakaue ki Maketu, Ngāti Mākino, Ngāti Pikiao and Tapuika—formed a collective called Te Wahapū o Waihī and began collaborating with the regional council to return the mauri to this storied place.

White is the independent chair of the collective, and Paul-Burke the project lead. Today, along with project coordinator Roana Bennett (Ngāti Whakaue) and the council’s coastal catchments manager, Pim de Monchy, they’ve brought 10 teenagers with them to the estuary.

These rangatahi all whakapapa to this place, and have spent the summer helping collect data and restore the estuary while learning both coastal ecology and mātauranga Māori. “It was a call home,” says 15-year-old Bella Ngawhika (Ngāti Whakahemo)—the stories and science both give the whenua a deeper meaning, she says.

“To me, it’s all about the young rangatira standing up and doing it for ourselves,” adds 16-year-old Charles Butler (Ngāti Whakaue). “It’s really changed our perspective—our view of the environment and how we can restore it.”

Their hi-viz vests bright orange among the long grasses, the group walk along a stopbank on the edge of the Pongakawa River. Dairy cows graze on the far side—starting in the 1950s, the stopbanks and pumping stations claimed paddocks from the tides.

“Have you noticed that all the canals, all the awa that feed into our estuary, are straight?” Paul-Burke asks the students. “Weird, eh? Cos Papatūānuku, she don’t go straight. She meanders. So all of the paru from the land just goes whoosh, like a hydroslide—straight into the estuary.”

On a bright Nelson day in December 2023, students from Te Kura Kaupapa Maori o Tuia te Matangi help Cawthron scientists collect seagrass flowers in the Waimea inlet. Despite covering only 0.1 per cent of the ocean floor, seagrass meadows are highly efficient carbon sinks, storing up to 18 per cent of the world’s oceanic carbon. Fish love them too—when NIWA scientists carpeted a patch of sea floor off Coromandel with lush, fake seagrass, 19 species of fish and other animals immediately moved in.
New Zealand’s mangroves—Avicennia marina—are estimated to bank 120 tonnes of carbon per hectare in their trunks, roots, and the soil beneath them, with 88 per cent of the stuff held tight under the ground. They’re only found from the Bay of Plenty north, but these carbon-storing superstars have been spreading their coverage of our coasts by about four per cent a year.

On the other side of the stopbank is a flat expanse of empty farmland, 109 hectares of which has just been bought by the council (though the iwi collective helped to pay for it, using funding from the Ministry for the Environment). This spot was once called Te Heriheri, Paul-Burke says. It was a salt marsh, where the ancestors collected harakeke and tī kōuka leaves to weave into nets.

The easiest way to bring the back the repo, the wetlands, de Monchy explains, would be to simply switch off the pumping stations. “It would restore itself to repo with very little effort. The difficulty in doing that is a whole lot of people have bought farms and businesses that rely on that low ground-water level, and you have to find a way of compensating them for the loss of that business opportunity. So we’re looking for opportunities to create wetland without sending everybody in the catchment out of  business.”

Later this year, the council will split off the Te Heriheri farm’s wettest 30 hectares and sell the rest to a willing neighbour. With Te Wahapū o Waihī, they’ll breach the stopbank, let the tides in, plant natives. “For us, the wetland is a korowai,” explains Paul-Burke. “A cloak you put in front of the estuary to trap the pollution and sediment that’s coming in through the rivers or canals.”

That korowai will also help to defend the coastline against the storm surges and flooding climate change is bringing to our shores. And it will almost certainly trap carbon, too. The Nature Conservancy (TNC), an international NGO with offices in New Zealand, found out about the Waihī project and approached the council and iwi with an offer to collaborate.

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The organisation’s project manager, Olya Albot, sees real opportunity for salt marsh restoration, in particular, to generate cash in the form of voluntary blue carbon credits. Typically, she explains, these credits are bought by environmentally motivated and reputation-oriented companies, non-profits or individuals to offset their own greenhouse-gas emissions. And demand for them is outstripping supply.

Overseas, there’s already a firm scaffolding around various kinds of coastal blue carbon credits: good sturdy science and well-established monitoring, reporting and verification schemes. This makes it simpler for those working on restoration projects to prove they really are tying up carbon. New Zealand doesn’t yet have that sort of infrastructure. There’s no reason to doubt that our mangroves, seagrass beds and salt marshes will be carbon superstars, but so far, very little research has been done to stack that up.

Te Wahapū o Waihī—alongside six other projects TNC is piloting around New Zealand—provides a perfect opportunity to do that. Before and after the restoration of this estuary, Albot’s team will take sediment samples, and compare the carbon stored in each muddy plug.

This paddock at the edge of Kaipara Harbour was once salt marsh, and flooded during Cyclone Gabrielle. Farmer Gill Adshead says the family are keen to know whether rewilding it could make a significant difference to carbon storage. Here, the site is being sampled by The Nature Conservancy, an NGO which is running a pilot study at six sites around the country.
The Nature Conservancy (TNC) Aotearoa’s Blue Carbon pilot project, is looking at the potential of coastal wetlands to store carbon, provide rich biodiversity habitats and offer carbon credits.

They’re also measuring salinity and water temperature. Four times a year they will bring in an instrument that quantifies the movement of carbon dioxide, nitrous oxide and methane gases between the air and the soil, to figure out what’s being stored and emitted.

With that data in hand, advisory firm TerraCarbon will then help investigate how viable a carbon-credit scheme could be. Depending on how much the Waihī restoration site locks away each year, it’s possible that carbon credits on their own may not generate a fortune—although they would certainly help support the restoration efforts.

Paul-Burke points out a tiny school of īnanga in a small area of wetland that’s recently been reshaped and replanted, in part to provide breeding habitat for this beloved whitebait species. Bennett, the project coordinator, emphasises that for the five iwi, any potential carbon credits are just a bonus. “Our core mahi here is to restore the estuary.”

That’s the focus for the council, too, says de Monchy. “The blue carbon work isn’t the driving force—it’s kind of like a nice cherry on the top. If it works, great. And if it doesn’t work, there are still lots of reasons it’s a good idea to restore this place.”

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There’s also a lot of excitement about seaweeds. Some start-ups have proposed building offshore farms where they would grow vast quantities of seaweed at the surface and then sink it into the ocean depths, perhaps after extracting a few key pharmaceuticals first.

It’s a simple concept, but a lot of science needs to be done before these ideas are even remotely plausible as carbon offsets, says seaweed expert Catriona Hurd from the University of Tasmania. Seaweeds do store carbon in their graceful fronds and stems—but kelp forests are a bit different from mangroves and salt marshes and the bush.

Trees pull carbon from the atmosphere and store it underground and in their wood for tens, hundreds, even thousands of years. Mangroves and seagrasses trap it among their roots and rhizomes, creating carbon-rich soil. In the carbon cycle, these time outs—ideally lasting 100 years or longer—are what make a difference for slowing the heating of the planet.

But seaweeds don’t live anywhere near as long as trees, and unlike the seagrasses, they don’t make soil, holding fast instead to rocks. A kelp frond’s contribution to sea-floor carbon lies entirely in whatever pieces of it make it to the bottom and get buried in mud for a century or more—without first being eaten by animals or decomposed by bacteria.

From place to place, and species to species, that contribution still needs to be worked out. Globally, Hurd says, it’s thought seaweeds are responsible for less than one per cent of long-term carbon storage pools in ocean sediments—the rest is all the work of phytoplankton. But New Zealand has lots of bushy brown macroalgae, and good environments for growing it—so how does it compare?

NIWA doctoral student Mari Deinhart collects seaweeds from Wellington’s wild coasts to test how quickly different species break down, and how they’re likely to contribute to carbon stocks in deep-sea environments. Whatever the results, she says, the research “will tell us a really incredible story of what’s going on in these habitats we hardly get to see, let alone study.”

In a dark, fridge-like room at NIWA’s Wellington offices, dozens of seaweed samples are rotting under layers of mud in plastic buckets. It’s a chilly six degrees in here, and each bucket is wrapped in a slice of pastel-coloured foam mattress to keep it cool, mimicking conditions 900 metres below the surface of Cook Strait.

A year ago, Victoria University of Wellington and NIWA doctoral student Mari Deinhart collected samples of native brown macroalgae—Cystophora, Carpophyllum, Macrocystis, Ecklonia, and Lessonia—from the capital’s southern coasts. She tried to head out after storms, so she could collect free-floating fragments that nature had already ripped off—as a seaweed-lover, she didn’t want to kill plants if she didn’t have to.

Some of the samples were placed in seawater, and others in sediments Deinhart’s NIWA colleagues hauled up from the bottom of Cook Strait for her. “I’m becoming known as ‘mud girl’,” she says. Every month, Deinhart removes four samples from each species and takes a bundle of measurements: environmental-DNA tests (see feature page 94), stable isotope and chemical biomarker analyses, and weight.

In a separate study, she’s collecting more mud from the depths of the Kaikōura Canyon and the mouth of the Marlborough Sounds. She’s looking for any traces of carbon that used to be seaweed, testing along a gradient from the coast to the deeps. She’s trying to understand how quickly different species of seaweed break down in the water column, and how much carbon each sequesters in these two different deep-sea environments.

If the algae decompose quickly, before they can be buried in the mud, more of their carbon is likely to be lost back to the atmosphere. Already, the difference between species is stark. In Deinhart’s experiments, the Macrocystis/giant kelp samples broke down completely after a few months, whereas the Lessonia and Carpophyllum are still kicking on a year later.

Deinhart’s work will be an essential first step for potential seaweed blue carbon projects here in New Zealand. But there’s another way kelp is extra tricky, says Hurd. Seaweeds take up carbon dioxide from the water, not the air. That patch of water will work to rebalance by slowly pulling in carbon from the air. But try measuring that.

“You’ve got to follow that water to work out how much carbon dioxide was drawn down,” says Hurd. “You’ll need an armada of sensors, and this is not trivial stuff to do. It’s going to cost a fortune.”

But without that information, she says, “we can’t accurately measure carbon dioxide removal by seaweeds”. She’s therefore intensely sceptical of the carbon component of seaweed aquaculture schemes—cutting our emissions, she notes, would be more straightforward.

“There’s no doubt that seaweed should be protected and restored, in that they’re critically important coastal ecosystems. But for carbon trading schemes? Almost certainly not.”

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Political appetite—for blue carbon, at least—is not a problem here. New Zealand First’s coalition agreement with the National Party promises to “progress work to recognise other forms of carbon sequestration, including blue carbon”. The Ministry for the Environment is already investigating including blue carbon in New Zealand’s greenhouse-gas inventory and our Emissions Trading Scheme.

Elizabeth Macpherson, a professor of law at the University of Canterbury, plans to spend the next five years mapping the legal and policy context of blue carbon schemes.

Our coastlines and oceans are subject to interlocking local, national, and international laws, property rights and customary rights, she says. Throw in unresolved Treaty of Waitangi claims and evolving court decisions. “It gets super complex really quickly.”

Her research, in partnership with Ngāi Tahu, will have a particular focus on how rangatiratanga might be embedded in blue carbon legislation and action. Macpherson—a former Treaty lawyer—knows that any exploration of blue carbon risks opening old wounds, especially those inflicted during the bitter fight over rights to the foreshore and seabed 20 years ago. “It’s extremely important that we don’t repeat any of the historical mistakes that we’ve made in terms of overriding Māori rights, interests and authority,” she says.

The prospect of using blue carbon schemes to pay to restore areas of coast is promising, she says, but would have to be set up with care and foresight. “This has to be right for our place.”

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When Kura Paul-Burke’s father was dying, the one food he wanted in those last days was pipi. Where from, she asked? “He gave me one of those looks that only your father can give you.” He meant Waihī. The whānau waited for the incoming tide—healthier water, fewer contaminants—and got him his pipi.

The shellfish, she says, is an important tohu for the estuary—a symbol of its health or otherwise. “The role of our generation is to make sure that those same pipi are there for our mokopuna,” says Paul-Burke. “Otherwise we’ve failed. We call it inherent guilt: it’s kaitiakitanga, where you feel so responsible and obligated, but it’s a beautiful thing at the same time. This is how we identify as ourselves.”

There are other signs here, too, and some are hopeful: despite the degradation, the remaining salt marshes are still a stronghold of the secretive matuku, the Australasian bittern—a bird almost as rare as the kākāpō or takahē. “One of our tohunga, our wisdom man, he gave us the vision: ‘He oranga te wahapū, he oranga te iwi,’” says White. “‘Let the health of our estuary be a metaphor for the health and wellbeing of our people.’”

When today’s elders were young, they knew only the richness they could see and taste, and the stories of abundance and connection passed down. Paul-Burke’s generation is writing a new story: learning to value the sea also for what it hides, and holds safe.

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