A ute cruises along the windy, rugged coastline of State Highway 35.
On one side of this East Cape route is the Pacific, a vivid white and blue swirl, on the other, the dense Raukūmara forest.
Pōhutukawa tilt their branches across the highway, pointing the way to a narrow entrance. The ute makes a sharp turn up a gravel driveway overshadowed by massive tōtara. It stops, and all that can be heard is the occasional swoop of a kererū and the relentless shrill of cicadas.
Kararaina Te Puni gets out, hoists a sturdy, well-worn black box from the boot and trudges off into the forest. She’s been here before and knows exactly where she’s headed. Tucked in the scrub, Kararaina spots the glint of the instruments she placed here more than a year ago.
Over the past three years, Kararaina, an atmospheric scientist and PhD student, has been to the East Cape of New Zealand’s North Island more than a dozen times.
At carefully chosen sites – just inside the forest, out around the coast, and inland near the base of Mt Hikurangi – she has collected air samples each time.
Each sample contains a snapshot of the forest’s breath. Her goal is to collect air upwind and downwind of the forest to understand how much carbon dioxide (CO2) it absorbs.
Specifically, Kararaina is investigating the ability of New Zealand’s native forests to sequester carbon. Her work is part of CarbonWatch NZ, a five-year, NIWA-led research project to better understand the carbon processes across New Zealand.
She is looking at the vast Raukūmara Forest, 200,000 hectares of steeply dissected hillsides with many areas more than 1,300m above sea level – the largest mountain-to-sea forest landscape in the North Island.
Forests primarily act as carbon sinks, sucking up carbon dioxide from the air and using this through photosynthesis to form the building blocks they need for growth.
Indigenous forests cover about 6.2 million hectares in New Zealand, yet these mature, old growth forests are often overshadowed by exotic pine, their faster-growing, rapid carbon sequestering counterparts.
“People have always assumed our native forests are acting at equilibrium where the decay and release into the atmosphere is similar to the amount of carbon they take up,” Kararaina says.
Preliminary research using a limited number of atmospheric measurements suggested that this was not the case, and that native forests were likely taking up more carbon than previously thought.
Yet, that study did not include data from forests in the North Island, so it was not clear whether this effect was replicated across the country.
This earlier work provided the impetus for the CarbonWatch NZ project, and subsequently, for Kararaina’s PhD.
“Our native forests are dynamic ecosystems, ranging from low-lying shrubs to the massive tōtara, which are sustainable for a long time, far longer than the quick-fix solution we see with pine,” she says.
“If a mature indigenous forest down in Fiordland is taking up more carbon than we thought, what is happening up here in the Raukūmara forest?”
Kararaina works closely with the iwi-led Raukūmara Pae Maunga restoration project which manages the forest. Like Kararaina, they are driven by a strong passion for seeing the forest flourish and thrive.
Kararaina’s PhD has involved developing a new method and instrumentation to measure the air samples she collects, including to measure the uptake of carbonyl sulphide (COS) in the soil.
Similar in structure to carbon dioxide, COS enters plants and trees in the same way, but is not released. By measuring COS, Kararaina can get a better understanding of how the forest is storing carbon.
When she collects air samples in the forest, she uses metal cylinders embedded in the ground to collect flasks of air that has interacted directly with the soil.
“Just like the trees, the soil breathes gases in and out. I look at how the soils are breathing and what they are breathing in and out, and how that affects the composition of gases the trees breathe.”
From a single forest to an entire country
While Kararaina spends time in the field collecting atmospheric data, others in the team work on high resolution models that show how the air moved before arriving at Kararaina’s observing sites. That is where Daemon Kennett comes in.
Like Kararaina, he is in the final stage of his multi-year research looking at New Zealand’s native forests and the role they play in carbon sequestration. His research uses an atmospheric inverse modelling approach to estimate carbon uptake in forests and grasslands.
What started as a pilot project using data from just two stations, has expanded to five in situ sites across New Zealand and more than 10 years of atmospheric observations.
This is no easy feat, starting with an initial theory; a hypothesis of what the uptake and release of carbon may be and then running the model through a statistical analysis with atmospheric observations; “adding information into the system” to make an accurate estimate for what the carbon uptake is in forests and across New Zealand.
Daemon has also developed capability to include measurements from two of NASA’s CO2 observing satellites, making observations from places even if no in situ station is there.
As Kararaina describes it, their differing research adds to the tools used to look at carbon uptake across New Zealand.
Looking ahead
The Ministry for the Environment (MfE) reports annually on the country's carbon emissions and uptake through New Zealand's Greenhouse Gas Inventory. However, the research of the CarbonWatch NZ team confirms that we may be underestimating the role of native forests in this inventory.
Another modeller on the project, Dr Beata Bukosa – and Daemon’s PhD supervisor – has spent the past five years compiling a decade of the team’s atmospheric data – from 2011 to 2020 – into a crucial research paper.
The team’s findings could have implications for New Zealand’s greenhouse gas reporting, carbon credit costs, and climate and land-use policies.
They used an inverse modelling technique combining atmospheric greenhouse gases with a model showing how air is transported through the atmosphere to identify the CO2 sources and sinks.
They compared their results against New Zealand’s Greenhouse Gas Inventory as well as ‘bottom-up’ models. While the Inventory applies a combination of field inventory, modelling, and remote sensing to quantify forest carbon stocks and stock changes, the ‘bottom-up’ models use calculations based on ecosystem processes, land use and climate across the country. The NIWA-led inverse model showed greater CO2 uptake than both of these other methods, particularly across Fiordland native forests and extending up the West Coast.
Meanwhile, with CarbonWatch NZ having reached its end, Kararaina and Daemon are also wrapping up their PhDs.
For Kararaina, it’s her last time (for now) working in the Raukūmara Forest and time to head home. After three years of travel between the labs in Wellington and the East Cape, she has completed all her fieldwork and is almost at the end of her PhD.
But, she says: “This is just the first step in a long journey of understanding our native forests and their impact on our atmosphere.”
CarbonWatch NZ: A bird’s eye view of our carbon balance
CarbonWatch NZ was a five year $11.5 million Endeavour research programme funded by the Ministry for Business, Innovation and Employment that finished earlier this year. The research combined measurements of greenhouse gases in the air above New Zealand with high-resolution weather models that show where those gases came from, giving a bird’s eye view of the country’s carbon balance.
The project looks specifically at carbon emitted from fossil fuels and agriculture and reabsorbed by four important environments: forests, grasslands, pasture and urban.
By weaving together decades of atmospheric data with an expanding network of in situ atmospheric monitoring stations, the project has built a more complete picture of New Zealand’s carbon profile.
For CarbonWatch NZ programme leader Dr Sara Mikaloff-Fletcher this is crucial for building on previous findings.
In 2017 the team found a large carbon sink in the Fiordland Forest. Since then, they have discovered that this carbon sink is actually distributed across a larger range of indigenous forests throughout New Zealand.
“With current carbon strategies primarily focused on planting exotic pine, this new research offers fresh insights into how we can make more informed decisions about planting and land management to better support climate mitigation with significant biodiversity co-benefits,” says Dr Mikaloff-Fletcher.
Sharing research and knowledge
Once silent, pest-invaded, eroding, and facing ecological collapse, Raukūmara was on the brink of collapse. With restoration urgent, the Raukūmara Pae Maunga Trust was born.
An iwi-led group of Ngāti Porou and Te Whānau-ā-Apanui in partnership with the Department of Conservation, it’s the largest iwi-led pest eradication project in New Zealand.
For both Kararaina, and the wider CarbonWatch NZ team this partnership has presented a unique opportunity to work alongside the restoration project and investigate how carbon uptake changes as the pests are knocked back and the forest regenerates.
“Kararaina has created a space that brings together a western science approach and a mātauranga Māori approach. By doing this I believe the research is enabling the forest to thrive,” says Raukūmara Pae Maunga’s Michaela Insley.
Kararaina agrees and says the biggest highlight has been the relationships she has built in her work. “We have come together to support one another, share research, and educate rangitahi.”
Meanwhile, the forest is healing. The birds have returned. The trees have fruit.
Raukūmara Pae Maunga’s Rangitahi Wharepapa says Kararaina is no longer a visitor to the East Cape.
“She is part of this place, she has done all this mahi in the Raukūmara, for the Raukūmara, she is part of the Raukūmara.”