Fiordland's lush green wilderness is used to push New Zealand's brand overseas - and scientists suggest it could also be sucking up far more carbon dioxide than we realise. Photo / File
Fiordland's lush green wilderness is used to push New Zealand's brand overseas - and scientists suggest it could also be sucking up far more carbon dioxide than we realise. Photo / File
Fiordland's lush green wilderness is used to push New Zealand's brand overseas - and scientists suggest it could also be sucking up far more carbon dioxide than we realise.
Scientists have begun a new study that will use the spectacular region as a "natural laboratory" to answer long-standing questions around how much CO2 enters and leaves our atmosphere today.
It follows the striking findings of a recent study that suggested our forests and other areas could be pulling in 60 per cent more CO2 than we'd estimated, with native trees likely to thank for most of it.
Being able to accurately measure our greenhouse gas emissions was critical to predicting how climate change would affect us in the future.
But being able to measure those emissions demanded a clear understanding of what scientists call "fluxes" - CO2 being pulled out of and pushed into the atmosphere.
Fluxes in Fiordland, home to one of our largest native forests, have been particularly contested.
Getting the true picture could lie in a new method - developed by Niwa and based on permanent measurements of atmospheric CO2 concentrations at critical sites around the country - to quantify national CO2 sink and source fluxes.
By analysing these measurements, scientists could work out the country's net CO2 fluxes, which was crucial for reporting of national greenhouse gas emissions that New Zealand has pledged to slash by 11 per cent below 1990 levels, by 2030.
Niwa atmospheric scientist Dr Peter Sperlich said it was this new method that had indicated native forests in Fiordland may absorb much more CO2 than previously estimated.
In a project, supported with a $300,000 Marsden Fund grant, he and international colleagues will use Fiordland as a "natural laboratory" to build and test other new observational methods to quantify CO2 fluxes, on a regional scale.
The new method factored in monthly air sampling during phases when oceanic air was advected from the ocean towards Fiordland's coast, followed by the sampling of those same air masses after they'd passed over the region's forests and reached an inland site.
The bush of Fiordland National Park. Photo / Mike Scott
"This sampling strategy will enable us to interpret measurable differences between coastal and inland air as a function of trace gas exchange within Fiordland to derive a regional CO2 flux estimate."
The team would also draw upon a range of just-developed isotope tracers, each revealing the specific processes - such as CO2 being absorbed by plants or emitted by plants and soil - at play.
Importantly, isolated Fiordland represented an untouched ecosystem where scientists could hone in on small natural atmospheric signals that might otherwise be masked by large man-made ones.
Results of the new tracer tests would later be compared against those of two earlier, contradicting Fiordland-based studies, one of them based on tree physiology observations and the other based on atmospheric modelling.
The project stood to not just gain more clarity around Fiordland's contribution to our carbon budget, he said, but to offer a blueprint for similar studies elsewhere in the future.
"One of our goals is to determine the most efficient combination of atmospheric tracers to determine natural CO2 fluxes on regional scales with highest possible accuracy," he said.
"This may inform future tools to evaluate regional efforts to reduce CO2 emissions, inside and outside of New Zealand."
New Zealand scientists had already played a big part in a global scientific effort to gauge CO2 fluxes on a national scale.
"We expect that our study will further New Zealand's contribution to the improvement of existing methods to quantify and understand regional CO2 fluxes."
New Zealand and climate change
• Under present projections, the sea level around New Zealand is expected to rise between 30cm and 100cm this century. Temperatures could also increase by several degrees by 2100. • Climate change would bring more floods; worsen freshwater problems and put more pressure on rivers and lakes; acidify our oceans; put even more species at risk and bring problems from the rest of the world. • Climate change is also expected to result in more large storms compounding the effects of sea-level rise. • New Zealand, which reported a 23 per cent increase in greenhouse gas emissions between 1990 and 2014, has pledged to slash its greenhouse gas emissions by 30 per cent from 2005 levels and 11 per cent from 1990 levels by 2030.
