Tauranga's Waikareao Estuary walkway. A just-published study has pointed to the immense sequestering potential lying within in our coastal and marine ecosystems like estuaries and mangrove forests.
Tauranga's Waikareao Estuary walkway. A just-published study has pointed to the immense sequestering potential lying within in our coastal and marine ecosystems like estuaries and mangrove forests.
Repairing our degraded coasts could help suck up the equivalent carbon produced by tens of thousands of cars each year, reveals the first national stocktake of its kind.
While pine forests might first come to mind when we think of carbon sinks, a just-published study has pointed to the immensesequestering potential lying within our coastal and marine ecosystems.
Scientists have found habitats like mangrove forests, salt marshes and seagrass beds can trap carbon for hundreds or even thousands of years – making for a powerful natural asset for offsetting the climate-heating greenhouse gases we produce.
Around New Zealand’s coasts, many of these habitats, and the countless species that rely on them, are under threat after decades of decline.
Still, interest was quickly growing: a hui in Nelson last year drew dozens of experts and leaders from around the country, and blue carbon was specifically cited in the coalition agreement between National and NZ First.
In the new study published in the journal Restoration Ecology, marine ecologist Dr Richard Bulmer and colleagues set out to explore how reviving them might offer a win-win for our environment and climate goals.
Using 20 years of data, including satellite imagery and spatial mapping, they were able to quantify our blue carbon potential – with promising results.
They found New Zealand’s estuaries and coastal regions currently housed around 20,900ha of salt marsh, 30,500ha of mangroves and 61,300ha of seagrass.
Together, these areas sequester approximately 57,800 tonnes of carbon each year – or about the same as taking more than 40,000 cars off the road each year.
However, beyond that, the study identified nearly 88,000ha of low-lying land that could be suitable for blue carbon projects, with the potential to sequester an additional 91,680 tonnes of carbon annually.
“While it’s unlikely that carbon credits alone will offset all the costs of restoring coastal and marine ecosystems – like transitioning low-lying marginal farmland to saltmarsh or mangroves – they could still generate revenue for landowners,” said Bulmer, who serves as director of consultancy at Tidal Research.
“It could also provide an additional pathway to meet our domestic and international climate change targets, and a range of other ecological, social and cultural benefits that come with coastal restoration.”
Bulmer said further research to fully explore those benefits would be crucial for driving investment and efforts in the space.
“This needs to be part of collaborative action between iwi and hapū, central and regional government, researchers, business and community,” he said.
“A healthy marine ecosystem can support a thriving, sustainable blue economy, and vice versa, but action is needed now to prevent ecosystem decline and support ecosystem recovery.”
At Fiordland’s Waitutu Forest, scientists are trialing new remote sensing technology to get a better measure of native forestry's carbon-sucking capacity. Photo / Alex Fergus
The new study comes as scientists have been using helicopter-mounted 3D lasers to measure New Zealand’s native forests for their carbon storage potential.
Indigenous forestry covers about 6.2 million hectares of the country and have been shown to be particularly powerful carbon sinks, storing billions of tonnes of CO2 equivalent.
One new study, co-authored by Scion’s Dr Alan Jones, suggested mature natural forests could absorb extra carbon even when CO2 levels reached what the world is likely to see in 2050.
That natural benefit made it crucial to get an accurate picture of tree sizes currently in our native forests, which have been traditionally measured with manual instruments.
“Now we have more sophisticated measuring technology, such as remote sensing, at our disposal,” Department of Conservation science monitoring adviser Terry Greene said.
“However, we need to do rigorous testing and ground-truthing to ensure the new technology is giving us accurate data on the size of trees.”
At a field test site in Fiordland’s Waitutu Forest, Manaaki Whenua researchers are trialling light detection and ranging technology called LiDAR.
A second test site is being set up in Coromandel, with six further locations across New Zealand being planned.
Assuming planting from 2027, it estimates there could be plantings of indigenous trees of 5000ha in 2027 and 7500ha from 2028, and exotic planting of 10,000ha from 2027.
Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.
