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Construction workers' ancient swamp kauri discovery could aid research on global climate change

An environmental scientist is looking to a cache of swap kauri, found by construction workers at a West Auckland building site earlier this year, to better understand information about climate change.

The kauri has been radiocarbon dated to 45,000 years or more by NIWA scientists. It's is significant because it is 35,000 years older than expected and places it within a Paleolithic age of human prehistory.

NIWA’s principal scientist, Andrew Lorrey, said the data gained from the unearthed wood, found at the Nido furniture store site, could have considerable significance internationally. 

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, he said.

"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."

Initially, Mr Lorrey thought the swamp kauri was going to be less than 10,000 years in terms of radiocarbon dating, but experts now have enough certainty to establish a radiocarbon date of more than 45,000 years.

"That's much older than we expected," he said. "That time period was characterised by rapid climate changes, most probably caused by the northern hemisphere ice sheets and sea level fluctuating wildly. 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.

"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 four metres underground, but assistant site manager Lisa Wade, who is of iwi Ko Kahungunu kia Heretaunga me Rongowhakaata me Te Aitanga A Mahaki toku descent, identified the significance of the find straight away. 

Since the swamp kauri was sealed off underground, its timber was preserved in exceptional condition. But as the wood was saturated, scientists need 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," Mr Lorrey said.

He said it was hard to know precisely what scientists were dealing with until they measure it and try to match the ring patterns against other trees that have a close radiocarbon date. Scientists will run the barcode sequences against other reference chronologies that have already been dated to see if there's a match.

Mr Lorrey described the annual rings as "like a high-resolution time capsule".

"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."

The swamp kauri has been gifted to traditional Māori carvers ahead of the store's opening this summer.

The ancient swamp kauri found at an Auckland building site could help scientists better understand climate change. Source: Supplied