In February 2019, Mark Magee was scraping the bucket of his 40-tonne excavator through a hillside when it hit something 10 metres down that wouldn’t budge. Magee, a construction foreman, was clearing a platform for a new geothermal power plant near Ngawha, a tiny community in New Zealand’s Northland region, the long peninsula that stretches north from Auckland.
He called in extra excavators to help. Gradually, as the machines peeled away the mudstone encasing the obstinate object, they realised it was a tree. When the thing finally lay uncovered, it measured 20 metres long and 2.4 metres across, and weighed 59 tonnes. It was a kauri tree, a copper-skinned conifer endemic to NZ. The Maori hold the species sacred, and use its honey-coloured softwood for carvings and canoes. Though this kauri tree had clearly been buried for thousands of years, Magee was astonished to see leaves and cones stuck to its underside that were still green.
A local sawmiller named Nelson Parker was called in to examine Magee’s find; he had been digging up, processing and selling kauri logs like this one since the early 1990s. As soon as his chainsaw bit into the bark, he knew from the colour of the sawdust (dark yellow) and from the smell (subtle, resiny) that this tree was very old, and worth a lot of money.
Parker also knew that this swamp kauri, as the buried trees are known, would be of special interest to a group of scientists who study the information that the ancient trees have coded into their rings. After removing the massive root ball, he cut a 10-centimetre-thick slice from the base of the trunk and sent it to them.
What he couldn’t know then was that this particular tree held the key to understanding an ancient global catastrophe, and how it may have shaped our collective past.
Boom and bust
The kauri tree, , is one of the largest and longest-lived tree species in the world. An individual kauri can live for more than two millennia, reaching 60 metres tall and more than five metres in diameter. Today, the living trees grow only in remnant pockets in northern NZ, where they are listed as threatened. Yet for tens of thousands of years, kauri forests dominated a vast swath of the upper North Island. As the trees grew, they recorded information in their annual
