Ancient kauri with secrets to share
Niwa scientists are turning to ancient swamp kauri in search of clues to climates history.
Dr Andrew Lorrey said kauri was a special species, with a lifespan of up to 1000 years “if left to their own devices” and provided important insights into long-term climate change.
Swamp kauri is predominantly found in Northland, where trees, preserved in relic peat bogs for tens to hundreds of centuries, contain information about climate in the past and clues about what might happen in the future. Scientists use them to create a record of the weather going back centuries.
“These trees appeared to listen to what was going on with the El Nin˜o-Southern Oscillation, which is very important to our regional climate, as well as driving huge climate anomalies such as droughts and floods around the globe,” Dr Lorrey said.
“There are a couple of outstanding questions in climate science at the moment. One is how the El Nin˜o-Southern Oscillation will respond to global warming. A paleoclimate record can provide good information about that.”
In a paper published in the Quaternary Science Reviews, outlining the scientific potential of swamp kauri, Dr Lorrey write that scientists obtained climate data by taking a cross section of the trunk of swamp kauri and measuring the width of the rings
"There are a couple of outstanding questions in climate science at the moment. One is how the El Nin˜ oSouthern Oscillation will respond to global warming. A paleoclimate record can provide good information about that." Dr Andrew Lorrey, Niwa scientist
after cutting the cross section into radial strips, like the spokes on a bicycle wheel. After polishing, the tree ring samples were analysed under a microscope.
“One measurement after the other creates a ring width sequence that tells us about the environment the kauri grew in and how that varied through time, largely driven by climate. This provides us with a rich history of the range of natural variation New Zealand can experience.” The currently calendar-dated kauri tree ring record went back 4500 years.
“But further back than that we have segments of about 1000 or 2000 years scattered across 30,000 to 60,000 years ago, floating in time anchored by radiocarbon dates”.
Scientists were concerned, however, that time periods could be lost if they were not told about swamp kauri excavation sites. The accelerated rate of extraction and export was a paradox for science, providing new material but also meaning wood could be lost from unknown excavations.
“For instance, we have a big gap of wood between 13,000 and 27,000 years old. If we were to get our hands on that we would have a shot at putting together an absolutely epic calendardated tree ring record,” he said.
Links between scientists and the swamp kauri industry had improved following a period of rapid market growth between 2011 and 2014, when things were very difficult to keep track of. Most practitioners would now advise scientists where they’re going to open up a site so they could be there from the onset.
“There’s a lot of other information that we can record about trees at a site before they’re taken out of the ground. Even the direction the trees are pointing in can tell us about past storms,” Dr Lorrey said, adding that New Zealand was the only place in the world that had such preserved trees, creating the possibility of testing hypotheses about the role of the climate in major changes throughout history.
“That is one of its most exciting potentials,” he said.