Swamp kauri unearthed at the construction site of New Zealand's largest retail store could yield important insights about future climate change.
After being dug up at the site of the new Nido furniture store in Henderson, scientists assessed the kauri and found it was more than 45,000 years old - placing it within the Paleolithic age of human prehistory.
For that reason, Niwa principal scientist Dr Drew Lorrey expected the secrets locked within it would be of global interest.
Due to the sensitivity of kauri to regional climate patterns, important knowledge could be gained on how El Niño operated in the past and how it might change in the future.
"I thought initially it was going to be less than 10,000 years in terms of radiocarbon dating but we now have enough certainty to establish a radiocarbon date of more than 45,000," Lorrey said.
"That much older than we expected. It is rare to find a site where all the wood has the same date, so more work on the Nido wood is still required."
The ancient wood was discovered at a depth of four metres and assistant site manager Lisa Wade identified the significance of the find straight away.
The swamp kauri was sealed off underground which has kept the timber preserved in exceptional condition but as the wood was saturated, the scientists needed to let it dry for some time before they can investigate further.
"Once it's dry enough, we take it back to the lab and sand it down, so that we can see the rings clearly and measure the sequences. It's like a time barcode," Lorrey said.
"We'll then run those barcode sequences against other reference chronologies that have already been dated and see if we get a match.
"It will be interesting to see when these trees were growing, and if it tells us something about when a kauri forest may have been present there."
He said it was hard to know precisely what they were dealing with until they measured it and tried to match the ring patterns against other trees that have a close radiocarbon date.
But because kauri tree rings are annual, it was effectively a high-resolution time capsule.
If the swamp kauri was as ancient and unique as now believed, more significant
information could be retrieved from its discovery.
"That time period was characterised by rapid climate changes, most probably caused by the Northern Hemisphere ice sheets and sea level fluctuating wildly," Lorrey said.
"We think that by looking closely at these trees, we can learn something new about the global climate system.
"When we get all the data together on the same timescale, we'll get an interesting picture of climate and environmental changes on the planet."
Swamp kauri was an ideal natural archive to give indications of what's happening with El Niño in the Pacific region.
"Kauri contains patterns that appear sensitive to that particular climate mode, which has a strong impact on New Zealand. From examining El Niño's behaviour back in time, this wood could be a hugely valuable tool.
"It can help us examine periods of El Niño activity during the times when humans weren't around in the landscape to modify it.
"We can get a good picture of what's going on with this major climate mode, which impacts billions of people all over the world. It also gives us an idea about the range of natural climate variations that impact on New Zealand, which is important for planning future climate extremes."
The kauri has been gifted to traditional Māori carvers ahead of the store's opening this summer.
The find comes after a 60-tonne kauri log recovered from ground near Kaikohe was recently dated as being between 41,000 and 42,500 years old – making it the only tree found anywhere in the world that was alive during a mysterious shift in the world's magnetic field.